Assessing the Effectiveness of Limestone from Oterkpolu Area in the Eastern region of Ghana as a Suitable Adsorbent for Water Defluoridation A thesis presented to the: DEPARTMENT OF NUCLEAR SCIENCE AND APPLICATIONS SCHOOL OF NUCLEAR AND ALLIED SCIENCES UNIVERSITY OF GHANA By ERIC KWABENA DROEPENU; 10506650 B.Ed. Science (University of Education, Winneba), 2007 In partial fulfillment of the requirements for the degree of MASTER OF PHILOSOPHY IN NUCLEAR AND ENVIRONMENTAL PROTECTION JULY, 2016. University of Ghana http://ugspace.ug.edu.gh ii DECLARATION This is to certify that this thesis is the result of research work undertaken by Eric Kwabena Droepenu towards the Degree of M.Phil. Nuclear and Environmental Protection in the Department of Nuclear Science and Applications, School of Nuclear and Allied Sciences (SNAS), University of Ghana, Legon, under the supervision of Prof. Samuel B. Dampare and Dr. Dennis K. Adotey. ………………………… Date …………………….. Eric Kwabena Droepenu (Student) ……………………………… Date …………………….. Prof. Samuel B. Dampare (Principal Supervisor) ……………………………….. Date ……………………. Dr. Dennis K. Adotey (Co-Supervisor) University of Ghana http://ugspace.ug.edu.gh iii DEDICATION This work is dedicated to my whole family and friends. University of Ghana http://ugspace.ug.edu.gh iv ACKNOWLEDGMENTS My first and foremost thanks and appreciation go to the Most High God for Protecting and Guiding me, giving me the Sound Health, Wisdom and Knowledge throughout this research work. May His Sovereign Name be Praised now and forever more. With maximum respect and standing ovation, I sincerely salute my two able and indefatigable supervisors, Prof. Samuel B. Dampare and Dr. Dennis K. Adotey for working tirelessly day and night, painstakingly going through my write up. Actually, their constructive criticism, corrections, encouragement and pieces of advice they bestowed on me have contributed immensely in coming up to this far. My special thanks also go to Mr. John Senu, Mr. Courage Argbey, Mr. Nash O. Bentil and Miss Ruby Torto, all of Nuclear Chemistry and Environmental Research Centre, GAEC for their skilled technical assistance. The following also deserve special thanks for their enormous and selfless services rendered. They include; Mr. David Okoh Kpeglo of Radiation Protection Institute, GAEC, Mr Ekow Quagraine and Mr. Isaac Baidoo of GHAR-1- Reactor Centre, GAEC, Dr. Martin Egblewogbe, Miss Beatrice Agyapomah, Mr. Emmanuel Abitty, Mr Peter Duduchoge, Mr. Sedem Garr and Mr. Emmanuel Awunyo of the Earth Science and Physics Department, UG, Legon, and the management of the Limestone Companies (Agyapaado, Love and Fanj) contracted by GHACEM for granting the permission to have access to Oterkpolu site for sampling. Finally, my profound gratitude goes to my wife, Mrs. Veronica Adae-Dropenu, my parents, brothers, and Staff of Benkum Senior High School, Larteh-Akuapem, for their encouragement during the course of this study. May God be gracious unto them University of Ghana http://ugspace.ug.edu.gh v and lift His light of countenance upon them all and be a blessing to this present and future generations. University of Ghana http://ugspace.ug.edu.gh vi TABLE OF CONTENT DECLARATION .......................................................................................................... ii DEDICATION ............................................................................................................. iii ACKNOWLEDGMENTS ........................................................................................... iv TABLE OF CONTENT ............................................................................................... vi ABSTRACT ...................................................................................................................1 CHAPTER ONE ............................................................................................................3 INTRODUCTION .........................................................................................................3 1.1 Background to the Study ......................................................................................3 1.2 RESEARCH PROBLEM .....................................................................................8 1.3 RESEARCH OBJECTIVES ..............................................................................10 1.3.1 Principal Objective......................................................................................10 1.3.2 Specific Objectives .....................................................................................10 1.4 JUSTIFICATION ..............................................................................................10 CHAPTER TWO .........................................................................................................12 LITERATURE REVIEW ............................................................................................12 2.1 Water occurrence in Ghana ................................................................................12 2.2 Importance of fluoride and its environmental occurrence .................................12 2.3 Fluoride in Bongo ..............................................................................................14 2.4 Chemistry of fluoride .........................................................................................16 2.5 Fluoride in humans and its health effects ..........................................................17 2.5.1 Fluoride intake and metabolism ..................................................................17 2.5.2 Health effects of fluoride ingestion .............................................................18 2.6 Defluoridation techniques/methods ...................................................................21 2.6.1 Precipitation method ...................................................................................22 University of Ghana http://ugspace.ug.edu.gh vii 2.6.2 Chemical method ........................................................................................23 2.6.3 Adsorption/Ion-exchange method ...............................................................23 2.6.3.1 Adsorption............................................................................................24 2.6.3.2 Types of Adsorption ............................................................................25 2.6.3.3 Factors affecting Adsorption................................................................25 2.7 Use of limestone as an adsorbent .......................................................................30 2.8 Natural Background Radioactivity ....................................................................30 2.8.1 Terrestrial Radionuclides ............................................................................31 2.8.2 Cosmogenic Radionuclide ..........................................................................33 2.8.3 Artificial (Man-made) Radionuclide...........................................................34 2.8.4 Transport, Fate and Distribution of Radionuclides in the Environment .....34 2.8.5 Effects of Radiation on Humans .................................................................35 2.8.6 Methods of Assessing NORMs ...................................................................35 CHAPTER THREE .....................................................................................................36 MATERIALS AND METHODS .................................................................................36 3.1 The Study Area ..................................................................................................36 3.1.1 Geographical location of Yilo Krobo-Oterkpolu ........................................36 3.1.2 Oterkpolu Limestone Deposits ...................................................................38 3.1.3 Commercial Mining of Oterkpolu Limestone.............................................38 3.2 Reconnaissance Survey ......................................................................................39 3.2.1 Ethical Approval .........................................................................................39 3.2.2 Site Visitation..............................................................................................39 3.2.3 Identification of Limestone during Site Visit .............................................39 3.3 Collection of Limestone .....................................................................................40 3.4 Sample Preparation and Analytical Methodology Development .......................41 University of Ghana http://ugspace.ug.edu.gh viii 3.4.1 General Overview of Experimental Work ..................................................41 3.4.2 Sample Preparation .....................................................................................43 3.4.2.1 Mineralogy Using Petrographic Thin Section .....................................43 3.4.2.2 Determination of Mineral Composition Using X-Ray Diffraction (XRD) ..............................................................................................................45 3.4.2.3 Assessment of Radiological Risk Posed by Oterkpolu Limestone ......47 3.5 Development of Limestone Defluoridation Technique using Batch Analysis ..53 3.5.1 Preparation of Limestone Samples .............................................................53 3.5.2 Batch Adsorption Experiment .....................................................................54 3.6 Application of Developed Technique ................................................................58 3.6.1 Collection of Water Samples from Bongo District .....................................58 3.6.2 Determination of Physico-chemical Parameters .........................................60 3.6.2.1. Determination of pH ...........................................................................60 3.6.2.2 Determination of Electrical conductivity (EC), Total Dissolved Solid (TDS), Turbidity, Colour and Salinity .............................................................60 3.6.3Column Adsorption Experiments ................................................................61 3.6.4 Determination of Cations ............................................................................62 3.6.4.1 Magnesium (Mg2+) ...............................................................................63 3.6.4.2 Determination of As by HG-AAS............................................................65 3.6.5 Determination of Anions.............................................................................66 3.6.5.1 Determination of Fluoride (F-), Chloride (Cl-), Phosphate (PO43-), sulphate (SO42-) and Nitrate (NO3-) using ICS-90 Chromatographic System .66 CHAPTER FOUR ........................................................................................................68 RESULTS AND DISCUSSION ..................................................................................68 4.1 Petrographic Thin Section..................................................................................68 4.1.1 Sample EKL R102 .......................................................................................69 University of Ghana http://ugspace.ug.edu.gh ix 4.1.2 Sample EKL D01 ........................................................................................69 4.2 XRD Analysis ....................................................................................................70 4.2.1 Limestone Samples EKL- R102 and EKL-D01 ..........................................71 4.3 Radiological Safety of the Limestone Samples .................................................71 4.3.1 Activity Concentration of Naturally Occurring Radionuclides in Limestone Sample..................................................................................................................71 4.4 Batch Adsorption Experiment ............................................................................74 4.4.1 General Procedure .......................................................................................74 4.4.2 Effect of Varying Residence Time on Residual Fluoride Adsorption in 1 mg/L Fluoride Solution ........................................................................................75 4.4.3 Effect of Varying Residence Time on Residual Fluoride Adsorption in 5 mg/L Fluoride Solution ........................................................................................83 4.4.4 Effect of Varying Residence Time on Residual Fluoride Adsorption in 10 mg/L Fluoride Solution ........................................................................................89 4.4.5 Effect of Grain Size on Percentage Mean Fluoride Adsorption .................96 4.4.5.1 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 1 mg/L NaF Solution..................................................96 4.4.5.2 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 1 mg/L NaF Solution ...................................................98 4.4.5.3 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 5 mg/L NaF Solution..................................................99 4.4.5.4 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 5 mg/L NaF Solution .................................................100 4.4.5.5 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 10 mg/L NaF Solution..............................................101 4.4.5.6 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 10 mg/L NaF Solution ...............................................102 4.4.6 Effect of Fluoride Concentration Variation on Percentage Mean Fluoride Adsorption..........................................................................................................103 University of Ghana http://ugspace.ug.edu.gh x 4.4.7 Effect of pH of Fluoride - Limestone Mixture on Percentage Mean Fluoride Adsorption..........................................................................................................105 4.4.8 Effect of Varying Adsorbent Dose on Percentage Mean Fluoride Adsorption..........................................................................................................106 4.5 Column Adsorption Experiment ......................................................................109 4.5.1 Anion Analysis from Column Adsorption Experiment ............................110 CHAPTER FIVE .......................................................................................................114 CONCLUSION AND RECOMMENDATIONS ......................................................114 5.1 CONCLUSION ................................................................................................114 5.1.1 Mineralogy ................................................................................................114 5.1.2 Radiological Safety ...................................................................................115 5.1.3 Particle Size - % Adsorption .....................................................................115 5.1.4 Resident Time - % Absorption .................................................................116 5.1.5 Adsorbent Dose - % Adsorption ...............................................................116 5.1.6 Fluoride Concentration - % Adsorption ....................................................117 5.1.7 pH - % Adsorption of Mixture (Limestone - Fluoride solution) ..............117 5.1.8 Column Adsorption ...................................................................................118 5.2 RECOMMENDATIONS .................................................................................119 REFERENCES ..........................................................................................................120 APPENDIX A ............................................................................................................137 APPENDIX B: Petrographic Thin Section of limestone samples .............................144 APPENDIX C: Activity Concentrations of Samples……………………………….149 APPENDIX D: Batch Adsorption Analysis………………………………………...155 APPENDIX E: Preparation of NaF solutions ...........................................................158 APPENDIX F: Ion Chromatography .........................................................................160 University of Ghana http://ugspace.ug.edu.gh xi APPENDIX G: Standard Calibration Curve ..............................................................161 APPENDIX H: Batch Adsorption Analysis ..............................................................163 University of Ghana http://ugspace.ug.edu.gh xii LIST OF TABLES 2.1: Fluoride concentration in drinking water and its health effects ..........................14 2.2: Fluoride concentration distribution in groundwater (upper regions, Ghana) .................................................................................16 2.3: Fluoride composition in some major mineral .....................................................17 2.4: Fluoride content in some food crops in Bongo district .......................................21 3.1: Concentration (prepared and measured) of standard solutions using Ion Chromatograph ..............................................................56 4.1: Percentage composition of mineralogical content of selected samples ..............67 4.2: Comparism of reported activity concentrations with the present study ..............72 4.3: Absorbed Dose and Radioactivity Indices associated with Oterkpolu limestone samples ..........................................................................73 4.4: Percentage fluoride adsorption for 1 mg/L fluoride solution ........................103 4.5: Percentage fluoride adsorption for 5 mg/L fluoride solution ........................104 4.6: Percentage fluoride adsorption for 10 mg/L fluoride solution ........................104 4.7: pH variation of F- - Limestone mixture with % mean fluoride adsorption ....................................................................................106 4.8: Variation of Adsorbent Dose on % Fluoride Adsorption for sample EKL-R102 ....................................................................................107 4.9: Variation of Adsorbent Dose on % Fluoride Adsorption for sample EKL-D01 ....................................................................................107 4.10: Physico-chemical and anion analysis of water samples from Bongo district ....................................................................................110 4:11: Summary of the effect of co-existing anions in the water samples before and after the defluoridation process ................................................113 University of Ghana http://ugspace.ug.edu.gh xiii LIST OF FIGURES 2.1: Fluoride concentration in some soil samples in the Bongo district of Ghana ...........................................................................................................15 2.2: Stages of dental fluorosis ..........................................................................19 2.3: Skeletal fluorosis ..................................................................................................20 2.4: Effect of contact time on the removal of fluoride from natural groundwater sample ..............................................................................................................27 2.5: Effect of adsorbent dose on the removal of fluoride by gypsiferous limestone ..............................................................................................................28 2.6: The effect of pH of the solution on fluoride removal ......................................28 2.7a: Scheme of Uranium decay (U-238) series ..................................................32 2.7b: Scheme of Thorium decay (Th-232) series ..................................................33 3.1: Map of study area showing the location of Oterkpolu and limestone deposit ..............................................................................................................37 3.2: Packaging of identified limestone samples for transportation to the lab at GAEC .............................................................................................................40 3.3a: General Experimental framework ..............................................................41 3.3b: Detailed work layout of the study ..............................................................42 3.4a: Cutting of limestone into slabs ..........................................................................44 3.4b: Canada Balsam ..................................................................................................44 3.4c: Grinding wheel ..................................................................................................45 3.4d: Petrographic Microscope ..........................................................................45 3.5a: Crushing with Fritsch Pulverisette 2 Jaw Crusher ......................................46 3.5b: Milling with Fritsch Pulverisette 2 Mortar Grinder ......................................46 3.5c: Sieving sample with 63 µm mesh ..............................................................46 University of Ghana http://ugspace.ug.edu.gh xiv 3.5d: Pulverized and homogenized samples ..............................................................47 3.5e: Tools for transforming powdered samples to pellets ......................................47 3.5f: XRD Diffractometer ......................................................................................47 3.6a: Packaging of limestone sample in a 1L Marinelli beaker ..........................50 3.6b: HPGe Gamma detector for NORMs measurement ......................................50 3.7a: Shaking sample with Retsch AS 200 Vibratory Shaker ..........................53 3.7b: Sieved limestone samples ..........................................................................53 3.8a: Eluent standard solution ..........................................................................54 3.8b: Regenerant standard solution ..........................................................................54 3.9a: Weighing of limestone sample ..........................................................................57 3.9b: Magnetic stirrer of mixture ..........................................................................57 3.9c: IC for F- measurement ......................................................................................57 3.10: Uncapped boreholes at two affected communities in the Bongo District ..............................................................................................................58 3.11a: Mini-Column bed filled with adsorbent .................................................61 3.11b: Aliquots taken from the different mini-column beds ......................................61 3.12a: Samples being prepared for digestion ..............................................................62 3.12b: Samples on hot plate during digestion ...........................................................62 3.13: Example of a Chromatographic spectrum obtained ......................................66 4.1: Photomicrograph of sample EKL- R102 ..............................................................69 4.2: Photomicrograph of sample EKL D01 ..............................................................69 4.3: Diffractogram of limestone sample EKL-R102 (A) and EKL-D01 (B) ........................................................................................................71 4.4: Plot of activity concentration against limestone type ......................................71 4.5: Plot of residual fluoride concentration against time for 10 g mass University of Ghana http://ugspace.ug.edu.gh xv [500-1000 µm] sample in 1 mg/L NaF Solution ..............................................74 4.6: Plot of residual fluoride concentration against time for 50 g mass [500-1000 µm] sample in 1 mg/L NaF Solution .............................................75 4.7: Plot of residual fluoride concentration against time for 100 g mass [500-1000 µm] sample in 1 mg/L NaF Solution ................................................76 4.8: Plot of residual fluoride concentration against time for 10 g mass [1000-2000 µm] sample in 1 mg/L NaF Solution ...............................................77 4.9: Plot of residual fluoride concentration against time for 50 g mass [1000-2000 µm] sample in 1 mg/L NaF Solution ..........................................78 4.10: Plot of residual fluoride concentration against time for 100 g mass [1000-2000 µm] sample in 1 mg/L NaF Solution ........................................79 4.11: Plot of residual fluoride concentration against time for 10 g mass [2000-6350 µm] sample in 1 mg/L NaF Solution ..................................80 4.12: Plot of residual fluoride concentration against time for 50 g mass [2000-6350 µm] sample in 1 mg/L NaF Solution ......................................80 4.13: Plot of residual fluoride concentration against time for 100 g mass [2000-6350 µm] sample in 1 mg/L NaF Solution ....................................81 4.14: Plot of residual fluoride concentration against time for 10 g mass [500-1000 µm] sample in 5 mg/L NaF Solution ............................................82 4.15: Plot of residual fluoride concentration against time for 50 g mass [500-1000 µm] sample in 5 mg/L NaF Solution .........................................83 4.16: Plot of residual fluoride concentration against time for 100 g mass [500-1000 µm] sample in 5 mg/L NaF Solution ...............................................84 4.17: Plot of residual fluoride concentration against time for 10 g mass [1000-2000 µm] sample in 5 mg/L NaF Solution .........................................84 University of Ghana http://ugspace.ug.edu.gh xvi 4.18: Plot of residual fluoride concentration against time for 50 g mass [1000-2000 µm] sample in 5 mg/L NaF Solution .......................................85 4.19: Plot of residual fluoride concentration against time for 100 g mass [1000-2000 µm] sample in 5 mg/L NaF Solution ......................................86 4.20: Plot of residual fluoride concentration against time for 10 g mass [2000-6350 µm] sample in 5 mg/L NaF Solution .....................................86 4.21: Plot of residual fluoride concentration against time for 50 g mass [2000-6350 µm] sample in 5 mg/L NaF Solution ......................................87 4.22: Plot of residual fluoride concentration against time for 100 g mass [2000-6350 µm] sample in 5 mg/L NaF Solution ......................................88 4.23: Plot of residual fluoride concentration against time for 10 g mass [500-1000 µm] sample in 10 mg/L NaF Solution ......................................89 4.24: Plot of residual fluoride concentration against time for 50 g mass [500-1000 µm] sample in 10 mg/L NaF Solution ......................................90 4.25: Plot of residual fluoride concentration against time for 100 g mass [500-1000 µm] sample in 10 mg/L NaF Solution ....................................90 4.26: Plot of residual fluoride concentration against time for 10 g mass [1000-2000 µm] sample in 10 mg/L NaF Solution ...................................91 4.27: Plot of residual fluoride concentration against time for 50 g mass [1000-2000 µm] sample in 10 mg/L NaF Solution ...................................92 4.28: Plot of residual fluoride concentration against time for 100 g mass [1000-2000 µm] sample in 10 mg/L NaF Solution ....................................92 4.29: Plot of residual fluoride concentration against time for 10 g mass [2000-6350 µm] sample in 10 mg/L NaF Solution ...................................93 4.30: Plot of residual fluoride concentration against time for 50 g mass University of Ghana http://ugspace.ug.edu.gh xvii [2000-6350 µm] sample in 10 mg/L NaF Solution ......................................94 4.31: Plot of residual fluoride concentration against time for 100 g mass [2000-6350 µm] sample in 10 mg/L NaF Solution ......................................95 4.32: Plot of % mean adsorption against mass of sample EKL-R102 in 1 mg/L ..................................................................................................96 4.33: Plot of % mean adsorption against mass of sample EKL-D01 in 1 mg/L ..................................................................................................97 4.34: Plot of % mean adsorption against mass of sample EKL-R102 in 5 mg/L ..................................................................................................98 4.35: Plot of % mean adsorption against mass of sample EKL-D01 in 5 mg/L ................................................................................................100 4.36: Plot of % mean adsorption against mass of sample EKL-R102 in 10 mg/L ................................................................................................101 4.37: Plot of % mean adsorption against mass of sample EKL-D01 in 10 mg/L ................................................................................................102 4.38: Plot of % fluoride adsorption for varying fluoride concentrations ............105 4.39: Plot of % fluoride adsorption against varying mass of samples ............108 4.40: Plot of residual fluoride concentration against time for water sample BNB6 ................................................................................................111 4.41: Plot of residual fluoride concentration against time for water sample BNB8 ................................................................................................111 University of Ghana http://ugspace.ug.edu.gh xviii LIST OF ACRONYMS AED Annual Effective Dose CEIA Centre for Environmental Impact Analysis DW Dry Weight EC Electrical Conductivity EKA Eric Kwabena Agyapaado EKL Eric Kwabena Love EPA Environmental Protection Agency HPGe High Purity Germanium IQ Intelligent Quotient LACOSREP Land Conservation and Smallholder Rehabilitation Project MSP Monosodium Phosphate NaF Sodium Fluoride NORMs Naturally Occurring Radioactive Materials NTU Nephelometric Turbidity Unit PHC Population and Housing Census PSU Practical Salinity Unit PTS Petrographic Thin Section TDS Total Dissolved Solids TENORM Technologically Enhanced Naturally Radioactive Materials VOC Volatile Organic Compound WHO World Health Organization XRD X-RayDiffraction University of Ghana http://ugspace.ug.edu.gh 1 ABSTRACT Fluoride-contamination of groundwater [above the World Health Organization (WHO) recommended limit of 1.5 mg/L] in the Upper East and Northern regions of Ghana is a well-known problem. Fluoride is, however, beneficial to humans if present in drinking water at levels between 0.7 – 1.5 mg/L. Although, there are some efficient methods for defluoridation of drinking water using various adsorbents, the magnitude of the problem has made it imperative to develop economically viable water defluoridation techniques using readily available natural resource as adsorbent. This will complement the existing defluoridation techniques in order to alleviate the difficulty faced by inhabitants of the affected communities. In addition, a method which is cost effective, easy to use by a layman, does not add other contaminants to water, and efficient in the long term is highly desirable. In this study, the effectiveness of readily available limestone from Oterkpolu (Yilo-Krobo district, Eastern region of Ghana) as fluoride adsorbent was assessed. A drinking water defluoridation technique was subsequently developed using the limestone with various grain sizes (i.e., 500 – 1000 μm, 1000 – 2000 μm and 2000 – 6350 μm) through Batch Adsorption Experiment (using NaF solution concentrations of 1, 5 and 10 mgF-/L), followed by Column Adsorption Experiment using fluoride contaminated groundwater water samples from Bongo district. This was achieved through the geochemical and mineralogical characterization of Oterkpolu limestone using X-ray Powder Diffraction (XRD) and Petrographic Thin Section (PTS). In addition, the radiological risk associated with the use of the limestone for water defluoridation was assessed through the determination of the activity concentration of the Naturally-Occurring Radioactive Materials (NORMs) using a High-Purity Germanium (HPGe) γ-ray detector [γ-ray spectrometry], and computed Annual Effective Dose (AED). The University of Ghana http://ugspace.ug.edu.gh 2 study also evaluated the fluoride adsorption efficiency (Sorption capacity and % Adsorption) of different limestone types from Oterkpolu with respect to varying: (i) adsorbent dose (ii) particle sizes of the adsorbent (limestone) (iii) residence time (iv) fluoride concentration. The developed technique was applied to fluoride contaminated water samples collected from affected the communities (Bongo district) through a Column Adsorption Experiment. From the Batch Adsorption Experiment, the maximum percentage adsorption of fluoride was 57.27%, 62.96% and 50.96% (for 1, 5 and 10 mg/L respectively) for sample EKL-R102 at the 60th minute. These results were recorded for 1000 – 2000 µm limestone grain size. The mean activity concentrations for 238U, 232Th and 40K were found to be 2.0 ±1.5, 1.7 ±1 and 21.9 ±13.4 Bq/kg respectively for the limestone samples from Oterkpolu. The calculated Annual Effective Dose of the adsorbent (0.027 mSv/yr) was lower than the recommended 0.40 mSv/yr proposed by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Mineralogically, (PTS and XRD analysis), the limestone sample is made up of 96% calcite and 4% quartz (PTS) and 83% calcite, 11% serandite and 6% silicon oxide (XRD). This indicates high calcite content in the sample which suggests that, it is an effective material for fluoride adsorption. The application of the developed methodology (Column Adsorption Analysis) yielded 80% and 67% fluoride removal from two groundwater water samples (BNN8 and BNB6) respectively from the Bongo district of the Upper East region of Ghana. Thus, the fluoride levels in the 330 mL samples were reduced from 7.5 and 6.2 mg/L to 1.5 and 2.0 respectively. The variation was as a result of co-existing anions present in the water sample. The results suggest that Oterkpolu limestone can be used effectively for the removal of fluoride ions in fluoride-contaminated groundwater in general and from the northern regions of Ghana in particular Bongo district. University of Ghana http://ugspace.ug.edu.gh 3 CHAPTER ONE INTRODUCTION 1.1 Background to the Study Water is an essential natural resource for sustaining life and the environment. The suitability of water for domestic, industrial or agricultural purpose depends on its chemical composition. Freshwater for use by humans occurs as surface water and groundwater (Meenakshi and Maheshwari, 2006). Though groundwater contributes only 0.6% of the total water resources on earth, it is the major and the preferred and only available source of drinking water in rural as well as some urban areas in developing countries (Meenakshi and Maheshwari, 2006). Preference for groundwater stems from the fact that it is generally of better quality and less polluted (MacDonald et al., 2000). Groundwater has excellent natural microbiological quality and generally adequate chemical quality for most uses (MacDonald et al., 2000). Groundwater is believed to be more potable and safer than surface water due to the protective qualities of the soil cover (Mishra et al., 2005). Though the initial cost for the construction of boreholes and hand-dug wells to harness groundwater are high, the operational costs are generally low as no chemical treatment is required (chemical treatment increases the operational cost for surface water). The cost of treating surface water is twice that of developing groundwater resources in communities with less than 5000 people (Dapaah-Siakwan and Gyau- Boakye, 2000). Fluoride (F-) contamination of groundwater has been recognized as a serious problem worldwide (Meenakshi, and Maheshwari, 2006). Fluoride is classified as one of the contaminants of water for human consumption by the World Health Organization University of Ghana http://ugspace.ug.edu.gh 4 (WHO), in addition to arsenic and nitrate, which cause large-scale health problems (Bhatnagara et al., 2011). Elevated fluoride concentrations in groundwater occur in various parts of the world (Gaciri and Davies, 1993; WRC Report, 2001). Fluoride is widely distributed in the geological environment (Abe et al., 2004) and generally released into the groundwater by slow dissolution of fluorine-containing rocks (Banks et al., 1995). Various minerals, like fluorite, biotites, topaz, and their corresponding host rocks such as granite, basalt, syenite, and shale, contain fluoride that can be released into groundwater (Edmunds et al., 2005; Apambire et al., 1997; Reddy et al., 2003). Therefore, groundwater is a major source of human intake of fluoride. Besides the natural geological sources for fluoride enrichment in groundwater, various industries are also contributing to fluoride pollution to a great extent (Reardon and Wang, 2000). Fluoride is thus considered beneficial in drinking water at levels of about 0.7 mg/L but harmful once it exceeds 1.5 mg/L, which is the World Health Organisation (WHO) recommended limit (WHO, 1985; Smet, 1990) and also the Australian recommended limit (Mohapatra et al., 2009). The difference between desirable doses and toxic doses of fluoride is ill-defined, and fluoride may therefore be considered as an essential mineral with a narrow margin of safety (WHO, 1984). Fluoride in drinking water has a profound effect on teeth and bones. Fluoride displaces hydroxide ions from hydroxyapatite, Ca5(PO4)3OH, which is the principal mineral constituent of teeth (in particular the enamel) and bones, to form the harder and tougher fluoroapatite, Ca5(PO4)3F. Up to a small level this strengthens the enamel. However, fluoroapatite is an order of magnitude less soluble than hydroxyapatite, and at high fluoride concentration the conversion of a large amount of the hydroxyapatite University of Ghana http://ugspace.ug.edu.gh 5 into fluoroapatite makes the teeth (after prolonged exposure, and the bones denser, harder and more brittle. In the teeth, this causes mottling and embrittlement, a condition known as dental fluorosis. With prolonged exposure at higher fluoride concentrations, dental fluorosis progresses to skeletal fluorosis (Dissanayake, 1991; Mohapatra et al., 2009). Owing to the high toxicity of fluoride to mankind, there is an urgent need to treat fluoride-contaminated drinking water to make it safe for human consumption. Several techniques have been developed for removal of fluoride from drinking water. The most commonly used methods for the defluoridation of water are adsorption, ion exchange, precipitation, Donnan dialysis and electrodialysis (Mohan and Pittman, 2007; Streat et al., 2008; Ahamad and Jawed, 2012). Among the various methods used for water defluoridation, the adsorption process is widely used; because it offers satisfactory results and seems to be a more attractive method for the removal of fluoride in terms of cost, simplicity of design and operation (Tripathy et al., 2004; Hichour et al., 2000; Ruiz et al., 2003; Srimurali et al., 1998; Reardon and Wang, 2000; Vaaramaa and Lehto, 2003; Singh et al., 1999; Amor et al., 2001). Various conventional and non-conventional adsorbents have been assessed for the removal of fluoride from water. these include activated alumina, amorphous alumina, activated carbon and low-cost adsorbents such as calcite, clay, charcoal, tree bark, saw dust, coffee husk, activated coconut shell carbon, activated saw dust, rice husk, groundnut husk and rare earth oxides (Srimurali et al., 1998; Reardon and Wang, 2000; Ghorai and Pant, 2004; Li et al., 2001; Ramos et al., 1999; Fan et al., 2003; Tripathy et al., 2004; Reardon and Wang, 2000). The removal efficiency and applicability of the existing fluoride removal methods often depend on various factors University of Ghana http://ugspace.ug.edu.gh 6 such as specific mineral concentrations in water, geographical and economic conditions, and availability of materials used for the removal. Some of the methods commonly used in most countries, adds harmful aluminium to water and need adjustment of pH (Suresh and Dutta, 2010; Meenakshi, and Maheswari, 2006). Although, there are some efficient methods for defluoridation of drinking water, a method which is cost effective, does not add other contaminants to water, economically viable, can be easily used by a layman and efficient in the long term is highly desirable (Suresh and Dutta, 2010). Over the past two decades, there has been a massive development of hand-dug wells and boreholes for use by people living in rural communities, especially in the Northern and the two Upper regions of Ghana. District Assemblies, the Community Water and Sanitation Agency (CWSA) of Ghana, non-governmental agencies (NGOs) notably ActionAid and World Vision have assisted most rural communities in Northern Ghana to enjoy safe and portable drinking water, as well as water for agricultural purposes through the provision of boreholes and hand-dug wells. This has helped alleviate poverty as the people mostly farmers have water all year round for their agricultural activities, in addition to improving the quality of drinking water. Notwithstanding, groundwater in some parts of northern Ghana have high levels of fluoride (above 4.5 mg/L) (Anongura et al., 2003; Apambire et al., 1997; Anongura, 1995; Anim-Gyampo et al., 2012). Communities affected by the high fluoride levels include Bongo, Tongo, Talensi and Bolgatanga districts (Upper East region). Others are, Gushiegu, Karaga, Saboba, Yendi and Chereponi districts (Northern region). Bongo, the worst affected community, has high cases of dental fluorosis, with Bongo University of Ghana http://ugspace.ug.edu.gh 7 township as the most affected. Available statistics indicate that about 63% of fluorosis cases were recorded in children from Bongo township, with about 9% of fluorosis cases in children outside Bongo township [fluoride concentrations outside Bongo township are generally below the WHO recommended level of 1.5 mg/L (Frimpong et al., 2013)]. Fluoride contamination of groundwater in Bongo and catchment area may be attributed to the geology of the area (granitoid rocks) (Brindha and Elango, 2013). As a result of weathering, the granitoid rocks dissolves, leading to the leaching of fluoride bearing materials (Fluorite and Apatite) into groundwater thereby elevating the fluoride levels (Nagendra Rao, 2003). This is illustrated in Equation 1.1 (release of fluorite due to weathering of apatite [Ca5(PO4)3F]: Ca5(PO4)3F + 3H+ 5Ca2+ + 3HPO42- + F- .................. (1.1) To help alleviate the high fluoride contents in waters from the Bongo district, a Project called “Sustainable Small Town Rural Water Supply System” jointly funded by the World Bank and the Ghana Government was initiated (GNA, 2014). Apart from this project, Non-Governmental Organisations (NGO) such as Rural Aid (a British NGO), World Vision International Ghana, European Union Micro-Projects Programme, ActionAid and the LACOSREP-II (Land Conservation and Smallholder Rehabilitation Project Phase II) have also provided quite a number of water and sanitation facilities in the district (GNA, 2014; Citifmonline.com, 2014). The Centre for Environmental Impact Analysis (CEIA) of the University of Cape Coast, Ghana, designed a local water project to reduce the high level of fluoride and iron in water at the Bongo district using local materials such as clay and laterite. According to the study, the technique removed about 75.3-85.6% fluoride, bringing it University of Ghana http://ugspace.ug.edu.gh 8 to the WHO acceptable range of 1.5 mg/L. Despite its high efficiency in fluoride removal, there is the introduction of iron into the water which is also of immense concern. The introduction of iron (Fe) may be due to the high iron oxide and aluminium content of clay and laterite. In view of the pervasive nature of the high fluoride contents in groundwater in the Upper East and Northern regions of Ghana, it has become imperative to help alleviate the fluoride problem in the affected communities by developing an economically viable water defluoridation technique using limestone as the adsorbent. The developed limestone-based method will complement existing defluoridation techniques being used by the inhabitants of the affected communities. 1.2 RESEARCH PROBLEM Groundwater is the main source of drinking water for majority of the communities in Northern Ghana and other parts of the world. Due to the geology of the area [(presence of granitoid rocks containing fluoride-bearing minerals (Fluorite and Apatite) in the case of Ghana] weathering of the rocks leads to the dissolution and leaching of fluoride into groundwater, thereby increasing the levels of fluoride. This has resulted in increasing reported cases of dental fluorosis among children in affected communities in Northern Ghana. As a result of the elevated fluoride levels in groundwater, drilled boreholes and hand- dug wells are often abandoned in spite of the large amount of money spent in drilling. School children walk long distances in search of water with acceptable fluoride levels. Often these children abandon the classroom. The issue of elevated fluoride levels University of Ghana http://ugspace.ug.edu.gh 9 constitutes a major setback in the socio-economic development of the people living in the affected communities. Therefore, provision of safe drinking water to the affected communities has become a matter of high priority to Governmental Agencies, Environmentalists and Medical Practitioners. To help alleviate the fluoride problem in the affected communities, there is an urgent need for the development of drinking water defluoridation techniques using locally-available fluoride adsorbents. Limestone or calcite, which is abundant in the severely fluoride-affected areas, is one of the potential materials for removal of fluoride; and has reportedly been used as adsorbent for fluoride removal (Suresh and Dutta, 2010). Accordingly, a defluoridation method using this low cost and readily available material (limestone) can be suitable for the affected areas in the Upper East and Northern regions of Ghana, considering Ghana’s large limestone deposits (8-10 million tonnes) [Iddrisu, 1987]. Ghana’s limestone deposits can be found in Otekpolu (Yilo Krobo district, Eastern Region), Nauli (Jomoro district, Western Region), and Bongo-Da (Nalerigu district, Northern Region), Limestone occurrences have been reported in the Buipe and Daboya (Northern Region of Ghana), Anyaboni (Upper Manya Krobo, Eastern Region), Sadan-Abetifi (Ashanti Region), and Du area (Upper Eastern Region) [Afenya, 1982; Kesse, 1975, 1985; Iddrisu, 1987]. Meanwhile no work has been done on these limestones to assess their effectiveness as a suitable adsorbent for removal of fluoride from drinking water. University of Ghana http://ugspace.ug.edu.gh 10 1.3 RESEARCH OBJECTIVES 1.3.1 Principal Objective The main objective of the study is to assess the effectiveness of limestone from Oterkpolu (a town in the Yilo-Krobo district, Eastern region of Ghana) as fluoride adsorbent and develop a drinking water defluoridation technique using the limestone. 1.3.2 Specific Objectives The specific objectives of the study are: i. to characterize Oterkpolu limestone geochemically and mineralogically; ii. to assess the Radiological Risk and Safety associated with the use of Oterkpolu limestone for water defluoridation [Activity Concentration(AC) and hence the Annual Effective Dose (AED)]; iii. to assess the fluoride adsorption efficiency (Sorption capacity and % Adsorption) of different limestone types from Oterkpolu (in a Batch Adsorption Experiment) with respect to varying: (a) adsorbent dose; (b) particle sizes of the adsorbent (limestone); (c) residence time; and, (d) fluoride concentration. iv. to apply the developed defluoridation technique to fluoride-contaminated water samples from Bongo district. 1.4 JUSTIFICATION Most rural communities in the northern regions of Ghana depend on groundwater for both domestic and agricultural purposes. Majority of the water from the dug wells in University of Ghana http://ugspace.ug.edu.gh 11 northern part of Ghana contains excess fluoride. Consequently, most of the wells have been abandoned, and this has caused huge financial deficit to the government and the affected communities (Atipoka, 2009). Such communities are also faced with the problem of looking for alternative sources of water. In view of the fluoride contamination problem, a user-friendly and cost effective technology is needed to defluoridate water using readily available and cheap natural raw materials. The use of limestone as a defluoridation material has been reported to be relatively efficient as compared to other methods. The reaction between Calcite (in limestone) with fluoride is very effective in defluoridation of water removal according to the reactions: CaCO3(s) + 2F-(aq) + 2H+ CaF2(s) + CO2(g) + H2O(l) (Raw limestone action) (1.2) CaCO3(s) + Heat → CaO(s) + CO2(g) (Quicklime production) (1.3) CaO(s) + H2O(l) → Ca(OH)2(aq) + 2F-(aq) CaF2(s) + O2- + H2O(l) (Quicklime action with F-) (1.4) Oterkpolu limestone samples were used for this study because it is the only limestone deposit in Ghana being mined currently for commercial purposes. University of Ghana http://ugspace.ug.edu.gh 12 CHAPTER TWO LITERATURE REVIEW 2.1 Water occurrence in Ghana Water is an essential natural resource for sustaining life and is among nature’s most valuable gifts. Once viewed as an infinite and bountiful resource, today, water often defines the limits of human, social, and economic development of a region. The Environmental Protection Agency (EPA) of Ghana in 1995 estimated that fresh water resources of Ghana have been estimated to about 40 million-acres and these are derived from the following sources: rainfall, rivers, streams, springs, lakes and groundwater from various aquifers. One of the main sources of freshwater for sustaining life on earth is groundwater. Unfortunately, groundwater is either being increasingly depleted for irrigation of crops, industrial, or other uses, or is becoming contaminated with various pollutants. Urban dwellers are more likely to have access to safe drinking water than rural dwellers at 91% and 69% respectively (GSS, 2011). Consequently, dependency on unsafe water sources is higher in the rural areas (http://www.water.org). Even with this statistics, it continues to dwindle due to factors such as rainfall variability (partly due to climatic changes), rapid population growth, increased environmental degradation and pollution of most water bodies (Dwamena-Boateng et al., 2011). 2.2 Importance of fluoride and its environmental occurrence Fluoride is a pale yellow green corrosive gas which cannot be found naturally in the environment in its elemental form. This is because it is highly electronegative and University of Ghana http://ugspace.ug.edu.gh 13 very reactive. Due to its small radius, it forms Ligands with organic and inorganic compounds in the soil, rocks, air, plants, animals etc. As a result, some of these compounds are soluble in water; both surface and groundwater (WHO, 1984). Fluorine rich minerals such as Fluorite (CaF2), Cryolite (Na3AlF6), and Fluoroapatite [Ca10(PO4)6F2] undergoes weathering which accumulate in water and soil (Murray, 1986). Water with high pH is believed to have high concentration of fluoride (Fawell et al., 2006). It is also noted that fluoride occurrence and their high concentration in water may be contributed by other factors such as Total Dissolved Solids (TDS), Alkalinity, Hardness and Geochemical composition of the aquifers (WHO, 1984; Mohan and Karthikeyan 1997; Abdelgawad et al., 2009; Meenakshi and Maheshwari, 2006). Moreover high concentrations of fluoride in water can also be attributed to anthropogenic sources. These are discharges of agricultural and industrial products such as glass, electronics, steel, aluminium, pesticides and fertilizers (Pietrelli, 2005), ceramics (Ponsot et al., 2013), coal fired power station, oil refineries etc (Shen et al., 2003; Bhatnagar et al., 2011). Fluoride therefore has both beneficial and detrimental effects on human health in terms of prevalence of dental caries, skeletal fluorosis and bone fractures, reproductive and immunological defects (Harrison, 2005; Valdez-Jimenez et al., 2011; Browne et al., 2005, Ayoob and Gupta, 2006). Dissanayake (1991) presented a typical fluoride concentration in drinking water and its associated health effects in the table below; University of Ghana http://ugspace.ug.edu.gh 14 Table 2.1: Fluoride concentration in drinking water and its health effects F- Concentration(mg/L) in drinking water Potential health effect a) ˂ 0.5 Minimal effect in prevention of dental caries b) 0.5 – 1.5 Beneficial effect in preventing dental caries c) 1.5 – 4.0 Dental fluorosis d) 4.0 – 10.0 Dental and skeletal fluorosis e) ˃ 10.0 Crippling fluorosis The amount of fluoride increases in the bones up to the age of 55 years but children are the most affected and remained crippled or deformed when high amount of fluoride is ingested (WHO, 1984). 2.3 Fluoride in Bongo Fluoride occurrence in groundwater is mainly controlled by two factors; geology and climate. The northern part of Ghana is mainly arid zone dominated by granitoid rocks underlining the geology. The upper regions are therefore considered as the most likely areas with high fluoride prevalence. Bongo district has an elevated fluoride in groundwater ranging between 1.7-4.0 mg/L (Atipoka, 2009). The district has 335 wells (boreholes, hand-dug wells and scoop wells) with depth ranging from 10-35 meters deep. Out of this number of boreholes, 35 are capped due to high fluoride content (Atipoka 2009). University of Ghana http://ugspace.ug.edu.gh 15 Apart from fluoride ingestion from water, soil is another medium from which plants and animals directly or indirectly derive their nutrients and food (Smedley et al., 1995; Pelig-Ba, 1987). As such, man consumes these products thereby increasing the fluoride concentration in the body. However information regarding the concentration of fluoride in the surrounding cultivated soils of the area is not widely publicised as that of water. In view of this no attention has ever been drawn to other sources except in water. But in a study by Abugri and Pelig-Ba (2011) on assessment of fluoride in tropical soils, samples were collected from selected communities known to have high fluoride concentration in their groundwater sources based on previous studies (Smedley et al.1995; Apambire et al., 1997; Pelig-Ba, 1998). The physical parameters considered were pH, soil depth and specific electrical conductivity of all the soil samples. The soil samples showed various concentrations of fluoride as indicated in the figure below. Fig 2.1 Fluoride concentration in some soil samples in the Bongo district of Ghana University of Ghana http://ugspace.ug.edu.gh 16 Apambire et al (1997) also investigated the distribution of fluoride in groundwater of the Upper Regions of Ghana and the results presented in the table below. Table 2.2: Fluoride concentration distribution in groundwater (upper regions, Ghana) Total No. of wells studied in entire Upper Regions No. of Bongo granite wells Range of Fluoride Conc. obtained (mg/L) 49 0 0.11 – 0.25 133 0 0.26 – 0.50 88 7 0.51 - 1.00 16 16 1.01 - 1.50 24 24 1.51 - 2.00 14 14 2.01 - 2.50 23 23 2.51 - 3.00 12 12 3.01 - 3.50 7 7 3.51 - 4.00 5 5 4.01 - 4.60 Total 371 108 2.4 Chemistry of fluoride Fluoride belongs to the group of halogens (Group VII) on the periodic table with atomic number 9 and an oxidation number of -1. With an electron affinity of 83.5 ± 2 kcal/g-atom, it is highly electronegative and very reactive to all elements except Oxygen and Nitrogen (Greenwood and Earnshaw, 1998; Macomber, 1996). Fluorine is characterised by a pungent odour and strongly irritant and very corrosive. Low calcium and high bicarbonate alkalinity favours high fluoride content in groundwater (Meenakshi and Maheshwari, 2006). It occurs in sedimentary and University of Ghana http://ugspace.ug.edu.gh 17 igneous rocks and associated with volcanic activities and with thermal water with high pH. The major minerals which contain fluoride are in Table 2.3. Table 2.3: Fluoride composition in some major mineral Mineral Chemical formula % fluoride Sellaite MgF2 61 Villiamite NaF 55 Fluorite (fluoraspar) CaF2 49 Cryolite Na3AlF6 45 Bastnaesite (Ce,La)(CO3)F 9 Fluorapatite Ca3(PO4)3F 34 [Source: Rao, 2003] Fluoride forms very strong bonds with carbon making it resistant to chemical and biological attack but can be substituted for hydrogen atoms and hydroxyl ions in molecules. 2.5 Fluoride in humans and its health effects 2.5.1 Fluoride intake and metabolism Fluoride ingested in small amount has beneficial effects on the rate of occurrence of dental caries among children (Mahramanlioglu et al., 2002). But on the contrary, excessive exposure to fluoride in drinking water leads to various health effects such as osteoporosis, arthritis, brittle bones, cancer, infertility, brain damage, Alzheimer syndrome and thyroid disorder (chinoy, 1991; Harrison, 2005; Xiang, 2003). University of Ghana http://ugspace.ug.edu.gh 18 A survey conducted in 1993 for 1,558 students in the Bongo district recorded 62% of the students (966 students) suffering from dental fluorosis (Duah, 2002). When tooth enamel which is made up of crystalline hydroxyapatite 2[Ca5(PO4)(OH)], gets into contact with food or water containing fluoride, the ion gets incorporated into the apatite crystal lattice of the calciferous tissue enamel during its formation. The hydroxyl ion gets substituted by the fluoride ion since the fluoroapatite is more stable than the hydroxyapatite. 2[Ca5(PO4)(OH)] + 2F- → 2[Ca5(PO4)F] + 2OH- (2.1) When fluoride in water is taken into the body system, about 50% of the fluoride is retained onto the teeth surface (surface uptake). The remaining 50% gets to the stomach as Hydrofluoric acid (HF). As a result of the acidic nature of the stomach, the HF diffuses into the blood plasma which is distributed to all parts of the body. Fluoride that is not absorbed into the blood stream as a result of high pH disrupts oxidative phosphorylation, glycolysis, coagulation and neurotransmission leading to gastro-intestinal irritation or corrosive effects (Islam and Patel, 2007; 2011). The absorbed fluoride (from the blood plasma) which is now available to the skeletal structures are retained and stored in proportions that increase with age and intake resulting in skeletal fluorosis. Meanwhile soft tissues do not retain fluoride (Raymond, 1999). 2.5.2 Health effects of fluoride ingestion It is well known that toxicity is determined by the dosage that the body takes as proposed by the Swiss Physician, Paracelsus (1493-1541). The body needs fluoride to build strong dental structures but when it exceeds the maximum permissible limit of University of Ghana http://ugspace.ug.edu.gh 19 1.5 mg/L (WHO, 2008), it results in negative effects ranging from dental caries to brain defects. Dental fluorosis is define as hypomineralization of the enamel characterised by greater surface and subsurface porosity than in normal enamel as a result of excess fluoride intake during the period of enamel formation (Browne et al., 2005). Dental caries also known as tooth decay on the other hand is a breakdown of the teeth due to activities of bacteria. This occurs due to acid made from food debris or sugar on the tooth surface. Minerals are added to and lost from a tooth's enamel layer through two processes, demineralization and remineralisation. Minerals are lost (demineralization) from the tooth's enamel layer when acids formed from plaque bacteria and sugars in the mouth attack the enamel. Minerals (fluoride, calcium, and phosphate) are redeposited (remineralisation) onto the enamel layer from the foods and waters consumed. Too much demineralization without enough remineralisation leads to tooth decay. The figure below shows the various stages of dental fluorosis. Fig 2.2 Stages of dental fluorosis [source: http://en.m.wikipedia.org/wiki/dental_fluorosis] University of Ghana http://ugspace.ug.edu.gh 20 Skeletal fluorosis affects both children and adults. It fully shows up when the disease attains an advanced stage (osteoporosis). The gradual intake and storage of fluoride increases bone formation in trabecular bones which exerts a greater response in the axial skeleton than in the appendicular. This could even lead to osteosarcoma (bone cancer) (Meenakshi Maheshwari, 2006) Fig 2.3 skeletal fluorosis [source: source: http://en.m.wikipedia.org/wiki/skeletal_fluorosis] According to the US Research Council, 2006, fluorides have the ability to interfere with the brain tissues resulting in mental retardation (IQ ˂ 70). Even in endemic areas, it could affect the development of children’s intelligence (Xiang, 2003). Ingestion of fluoride is not only through drinking water but some foods such as fish and other seafood (Shomar et al., 2004). This research is corroborated by Abugri and Pelig-Ba, 2011 when they determine the level of fluoride (F-) in cultivated soils in the Bongo district and its implication to crops. The F- content in the soils ranged from 219.26 to 1163.01 mg/kg dry weight (DW). Table 2.4 gives the fluoride content in some food crops in the Bongo district (unpublished document) by Asamoah-Antwi Dinah. University of Ghana http://ugspace.ug.edu.gh 21 Table 2.4: Fluoride content in some food crops in the Bongo district PLANT SAMPLES Ca 2+ (mg/kg) Mg 2+ (mg/kg) F - (mg/kg) Bito (Amanga) 24.047 4.86 263.90 Bito (Bongo central) 24.038 8.51 213.45 Millet (Bongo central) 40.078 6.08 267.26 Okro (Bongo central) 22.023 4.25 208.97 Millet (Tapentin) 22.043 4.86 223.54 Okro (Tapentin) 20.039 4.86 196.64 Guinea corn (Tapentin) 26.051 4.86 278.48 Groundnut (Tapentin) 24.027 7.29 228.03 Groundnut (Navrongo) 22.009 2.43 126.01 Bito (Navrongo) 18.035 2.43 87.89 Okro (Navrongo) 20.039 3.65 113.68 [The F- levels in plants were beyond the maximum F- level recommended in food stuffs (0.2-0.5 mg/kg) (US EPA, 1989; 1995; 2003, WHO, 2001; 2002).] Tea drinks have a very high fluoride levels and when consumed regularly, results in high risk of fluoride toxicity (skeletal fluorosis) [Xiang, 2003]. According to a survey carried out in the US, the fluoride content in tea ranges from 0.1- 4.2 ppm with an average of about 3 ppm (Levy and Guha-Chowdhury, 1999). 2.6 Defluoridation techniques/methods To mitigate the problem of fluoride contamination in water, many methods have been developed. It has been concluded that the selection of treatment process should be site University of Ghana http://ugspace.ug.edu.gh 22 specific as per local needs and prevailing conditions as each technology has some limitations and no one process can serve the purpose in diverse conditions. The most commonly used ones include precipitation, membrane filtration and adsorption/ion exchange. 2.6.1 Precipitation method This method involves the addition of calcium and phosphate compounds in contact with an already saturated bone charcoal medium. Calcium fluoride and/or fluoroapatite is precipitated as this method is theoretically feasible, but practically impossible due to slow reaction kinetics. The removal of fluoride from the system is aided by the use of calcium chloride and Sodium Dihydrogenphosphate [Monosodium Phosphate (MSP)] in the following reaction equations. CaCl2 + 2H2O ⇄ Ca2+ + 2Cl- + 2H2O (calcium chloride dissolution) (2.2) NaH2PO4H2O ⇄ PO43- + Na+ +2H+ + H2O (MSP dissolution) (2.3) 10Ca2+ + 6PO43- + 2F- ⇄ Ca10(PO4)6F2 (precipitation of fluoroapatite) (2.4) Though, this method provides a high sorption capacity, the odour and taste of the water is affected due to organic leaching. Also, regular monitoring and maintenance is necessary as the filter needs to be regenerated or replaced. This method has been tested in Tanzania which shows a promising result. University of Ghana http://ugspace.ug.edu.gh 23 2.6.2 Chemical method This method involves the addition of chemicals (lime, magnesium or aluminium salts along with coagulant materials) to the water to precipitate the fluoride. The process is aluminium sulphate [Al2(SO4)3.18H2O] based coagulation-flocculation sedimentation, where the dosage is designed to ensure fluoride removal from the water. Aluminium hydroxide micro-flocs are produced rapidly and gathered into larger settling flocs with the negatively charged fluoride ions attached (Fawell et al., 2006). The following equations illustrate the removal process. Al2(SO4)3.18H2O ⇄ 2Al3+ + 3SO42- + 18H2O (Alum dissolution) (2.5) 2Al3+ + 6H2O ⇄ 2Al(OH)3 + 6H+ (Aluminium precipitation) (2.6) 6Ca(OH)2 + 12H+ ⇄ 6Ca2+ + 12H2O (pH adjustment) (2.7) A large dose of aluminium sulphate is required for this process which makes the medium acidic. Simultaneously, addition of lime is often needed to ensure neutral pH in the treated water and complete precipitation of aluminium. A large sludge is produce which is of a serious environmental health problem due to its toxicity (Fawell et al., 2006). The use of lime and magnesium renders the water unsuitable for drinking due to its high pH. This method is also known as the Nalgonda Technique (RGNDWM, 1993). 2.6.3 Adsorption/Ion-exchange method In this method, water is passed or run through a bed column containing defluoridating materials/adsorbents which retains the fluoride by either physical, chemical or ion exchange mechanisms. The material gets saturated after a period of operation and University of Ghana http://ugspace.ug.edu.gh 24 requires regeneration. Some of the materials used include Activated Alumina, Fly Ash (Chaturvedi et al., 1990), Silica gel (Wasay et al., 1996), Bone charcoal (Bhargava, 1992), Carbon nanotubes (Li, 2003) and some low cost geo-materials including soils (Wang et al., 1995; Wang and Reardon, 2001), Volcanic ash (Srimurali et al., 1998), Zeolites (Onyango et al., 2004) and Macrophyte biomass (Miretzky et al., 2008). Fluoride uptake by the adsorbent is by exchange of metal lattice hydroxyl or other anionic groups with the fluoride. 2.6.3.1 Adsorption Adsorption is the process through which a substance, originally present in one phase, is removed from that phase by accumulation at the interface of a second (solid) phase (Piero M. Armenante). Crittenden et al., (2005) define adsorption as a mass transfer process which a constituent in a liquid/gas phase is accumulated on a solid/liquid phase and separated from its original environment. The process therefore creates a film of the adsorbate (molecules or atoms being accumulated) on the surface of the adsorbent. Adsorption processes provide a feasible technique for the removal of pollutants from water and waste water (McKay, 1995). In general, adsorption proceeds through the following steps; mass transfer, intra-granular diffusion and physical adsorption. In principle, adsorption can occur at any solid-fluid interface. Examples include: gas-solid interface as in the adsorption of a VOC (volatile organic compound) on activated carbon; liquid-solid interface as in the adsorption of fluoride on limestone or activated carbon. University of Ghana http://ugspace.ug.edu.gh 25 The adsorbate or solute is the materials being adsorbed and the adsorbent is the solid material being used as the adsorbing phase. eg limestone, activated carbon, activated alumina, silica gel. 2.6.3.2 Types of Adsorption The nature of the bonding of the species involved classifies the phenomenon into the two main types. These are; Physical adsorption/Physisorption: In this type of adsorption, the force holding the species together is the weak Van der Waals forces. With this adsorption process, the chemical species of the adsorbate and the surface are left intact. Chemical adsorption/Chemisorption: this type is characterized by covalent bonding or electrostatic force of attraction. This process involves a chemical reaction between the surface and the adsorbate which generates a new chemical bonds at the adsorbant surface. 2.6.3.3 Factors affecting Adsorption Nature of adsorbent In adsorption studies, the rate of adsorption depends on many physicochemical features of the adsorbent to achieve a maximum result. These physical features include the surface area of the adsorbent, the porosity, the particle size, the molecular weight of the adsorbent, the solubility and the ionic radii of the species involved. From reaction kinetics theory, the lager the surface area, the higher the reaction rate. This implies that, the rate of adsorption will increase when the particle size is small or University of Ghana http://ugspace.ug.edu.gh 26 decreases. This is attributed to the fact that the smaller the particle size, the greater the surface area and the more the number of active sites available for adsorption process for a given amount of adsorbent (Gao et al., 2009). Smaller particle size reduce internal diffusional and mass transfer limitation to the penetration of the adsorbate inside the adsorbent thus equilibrium is more easily achieved and nearly full adsorption capability can be attained. The pore size distribution allows for effective migration of contaminants to the point of adsorption. The solubility of the adsorbate also plays a major role in the efficiency of adsorption. Higher solubility shows a strong solute-solvent interaction. The increase in the interaction in terms of the bond chain lenth increases the hydrophobicity of the molecules, hence resulting in a greater adsorption. On the other hand, since fluorine is having a smaller ionic radius, its interaction with positively active sites like calcium ions (Ca2+) becomes very strong and this enhances a greater process of adsorption. Contact time or residence time As the adsorbent spends more time with the adsorbate, percentage removal also increases initially until an equilibium is reached. The time to reach equilibrium appears to be independent of the initial fluoride concentration in the range of 5-20 mg/L (Das et al., 2005). Decreasing the contact or residence time results in a premature breakthrough therefore reducing the service time of the bed (Jusoh et al., 2007). The figure below shows the fluoride removal percentage versus contact time by Fufa (2014). University of Ghana http://ugspace.ug.edu.gh 27 Fig 2.4: Effect of contact time on the removal of fluoride from natural groundwater sample. Dose of adsorbent The influence of the adsorbent dose on fluoride removal can be looked at from two different perspectives. As the dose is increased, it also increases the active sites of the adsorbent which significantly increases the adsorption rate. However, as the dose significantly increases, the adsorption rate tends to decrease which may be due to the overlapping of the active sites thereby decreasing the surface area of the adsorbent. A study carried out by Fufa (2014) using gypsiferous limestone in the removal of fluoride in water by varying the adsorbent from 1-20 g/L while keeping the other experimental conditions constant shows a significant increase of fluoride removal up to 60% of the 11.28 mg/L of the fluoride at an adsorbent dose of 15 g/L. University of Ghana http://ugspace.ug.edu.gh 28 Fig 2.5: Effect of adsorbent dose on the removal of fluoride by gypsiferous limestone Effect of pH The pH of a medium is important in predicting the efficiency of adsorption since hydrogen ion (H+) and hydroxide ions (OH-) are adsorbed relatively strongly. In an acidic medium, high quantity of particles are adsorbed since the positively charged adsorbent attracts fluoride ions electrostatically than in an alkaline medium since OH- compete with the fluoride ions leading to a lower defluoridation. Figure 2.6 is the results from a survey from Tor, (2006) of fluoride removal using montmorillonite Fig 2.6. Effect of pH of the solution on fluoride removal, University of Ghana http://ugspace.ug.edu.gh 29 Effect of interfering ions Groundwater contaminated with fluoride comes along with other anions such as chlorides, nitrates, bicarbonates and phosphates. The impact of interfering ions present in water on fluoride adsoption by activated carbon adsorbent follows the order; PO43- ˃ HCO3- ˃ SO42- ˃ NO3- ˃ Cl- (Suneetha et al., 2015). Previous research by Onyango et al., (2004) also indicated that chloride and nitrate ions has less interferences on fluoride adsorption as compared to sulphate ions. According to Suneetha, the alkalinity of the bicarbonate reduces the active sites on the active cabon thereby decreasing the percentage of fluoride removal. Tchomgui-Kamga et al., (2010), also have the assertion that sulphates, bicarbonates, nitrates, phosphates and calcium ions at a concentration of 100 mg/L have no significant effect on fluoride removal. But chlorides have a greater deal of influence because of their ionic radii [(Cl- = 3.32A and F- = 3.52A)]. Because of their radii, they are able to have higher mobility through the aqueous matrix and penetrate the adsorbent structure offering stronger competition for adsorptive sites thereby reducing the fluoride adsorption. Effect of flow rate Slower flow rate produces higher empty bed contact time and the adsorbate takes longer time to diffuse onto the solid phase of the adsorbing media. The shape of the breakthrough curve from lower flow rates are more approximate to the ideal breakthrough curve than the fast flow rate. The breakthrough curve for fast flow rates deviates more from the ideal breakthrough curve and thus results in a larger root mean square error value (Jusoh et al., 2007). University of Ghana http://ugspace.ug.edu.gh 30 2.7 Use of limestone as an adsorbent Limestone is a sedimentary rock largely made of mineral calcite (more than 50%) and aragonite (Folk, 1974). Other sedimentary rocks like carbonate rocks are dominated by dolomite [CaMg(CO3)2]. Most limestone is composed of grains of marine organisms such as coral of foraminifera. These organisms secrete shells made of aragonite or calcite behind when they die. Some limestones do not consist of grains but are formed by chemical precipitation of its minerals (Dunham, 1962). Another class of limestone also forms through evaporation. These are the stalactites, stalagmites and other cave formations (speleothems). They are formed as a result of droplets of water seeping down the fractures or other pore spaces in a cave ceiling where the water evaporates. Over time, the evaporative process results in an accumulation of icicle-shaped calcium carbonate on the cave ceiling. Limestone often contains variable amounts of silica and varying amounts of clay, silt and sand carried by rivers. All limestone contains at least a few percent of other materials such as quartz, feldspar, clay minerals, pyrites, siderites and other minerals (Folk, 1974). The calcium carbonate content of limestone gives it a property that is often used in rock identification-effervescence in contact with dilute hydrochloric acid. 2.8 Natural Background Radioactivity Natural radioactivity originates from outer space and the earth’s crust (cosmogenic and terrestrial). The parent sources of these radiations of natural origin are those from daughter products of U-238 series, Th-232 series and K-40. In addition to the University of Ghana http://ugspace.ug.edu.gh 31 Naturally Occurring Radioactive Materials (NORMs) from terrestrial and cosmogenic sources, Technologically Enhanced Naturally Radioactive Materials (TENORM) and man-made radionuclide from the environment due to the proliferation of different nuclear applications. The natural background radiation levels differ from place to place and are a function of properties of the underlying rocks and of the soil in the location, such as distribution of uranium and radium, porosity, permeability, moisture content as well as meteorological and seasonal variation (Merdanoglu and Altinsoy, 2006; Chowdhury et al., 2004). 2.8.1 Terrestrial Radionuclides Primordial radionuclides are long-lived species which have been present on earth since its formation about 4.5×109 years ago and are found around the globe in most rocks. These radionuclides formed from the decay of the Uranium, Thorium and Actinide series are the main sources of terrestrial radionuclides. Other important terrestrial radionuclides include the isotopes of Potassium-40, Vanadium-50, Rubidium-87, Cadmium-113 and Indium-115. The decay schemes of U-238 and Th-232 (Fig 2.7a and 2.7b) is shown below. University of Ghana http://ugspace.ug.edu.gh 32 Fig 2.7a Scheme of Uranium decay (U-238) series University of Ghana http://ugspace.ug.edu.gh 33 Fig 2.7b Scheme of Thorium decay (Th-232) series 2.8.2 Cosmogenic Radionuclide These are products (isotopes) of interactions of primary and secondary cosmic-ray particles with atomic nuclei (Dunai, 2010). There are both radioactive and stable cosmogenic isotopes. These include 3H, 10Be, 41Ca, 53Mn, 36Cl, 26Al, 14C, 32P, which are produced by the interaction of galactic cosmic rays with the earth’s atmosphere. University of Ghana http://ugspace.ug.edu.gh 34 Cosmic radiation is a mixture of many different types of radiation such as photons, alpha particles, electrons and other high energy particles. At the earth’s surface, more than 98% of the cosmogenic nuclide production arises from secondary cosmic-ray particles (Masarik and Beer, 1999). 2.8.3 Artificial (Man-made) Radionuclide Through man’s potential exploration of radioactivity in such fields like medicine, military, mining and power generation, there is the introduction of radiations order than the natural ones into the environment which have increased the natural background levels leading to enhanced concentration of natural radionuclides generally referred to us Technologically Enhanced Naturally Occurring Radioactive Materials (TENORMs). 2.8.4 Transport, Fate and Distribution of Radionuclides in the Environment The parent source of natural radionuclides (uranium and thorium series) in the earth crust release radioactive isotopes which dissolve into surrounding aquifers or readily absorbed by surrounding soil particles like clay, noted for its high absorption and ion exchange capacity (Emeka,2010). Hence, clays have higher concentrations of radioactive isotopes than that found in sand-stones (Solomon et al., 2002). Other radioisotope like radon gas, recognized as carcinogenic is soluble in water under high pressure finds its way to the surface of the earth through geological faults and cracks. These characteristics of radon were used to find geological faults and to predict seismic activities in some regions of the world (Singh et al., 2009; Bhongsuwan et al., 2011; Virk et al., 2000; H. Climent et al 1999). University of Ghana http://ugspace.ug.edu.gh 35 The fate and distribution of radionuclides in the atmosphere depends on the chemical and physical form of the radionuclide. Some radionuclides attaché readily to aerosol particles and are carried by wind. These are inhaled directly or are deposited on plants and find their way into the food chain. 2.8.5 Effects of Radiation on Humans Effects of NORMs account for about 80% of man’s exposure to natural radiation and the second leading cause of cancer after tobacco (USEPA, 2006; UNSCEAR, 2000). Long term exposure of these radionuclides has several health effects such as chronic lung diseases, acute leucopoenia, anaemia and necrosis of the mouth (Ramasamy et al 2009). 2.8.6 Methods of Assessing NORMs Radioactive contamination in soil and water can be determined by several laboratory methods. However, type of site, level of contamination at the site and the specific analysis needed will determine the type of methodology that will be appropriate (USEPA, 2006). The different types of determinations include; Liquid Scintillation Counting, Gas Extraction, Gamma Spectrometry and Alpha Spectrometry. University of Ghana http://ugspace.ug.edu.gh 36 CHAPTER THREE MATERIALS AND METHODS This chapter consists of seven (6) sections (Sections 3.1 to 3.6). Section 3.1 describes the study area (geographical location, the limestone deposit, and mining of the limestone). Section 3.2 is a description of the Application for Ethical Clearance to enter the concession, and Reconnaissance Survey undertaken (visit to Oterkplolu limestone deposit, identification of limestone deposits). In Section 3.3, the collection of the limestone samples was described. General sample preparation is described in Section 3.4. In Section 3.5, the development of the limestone defluoridation technique using Batch Adsorption experiments are described. Application of the developed technology is described in Section 3.6. 3.1 The Study Area 3.1.1 Geographical location of Yilo Krobo-Oterkpolu Oterkpolu, (6” 12’ 0” North; 0” 70’ 0” West), is a small farming community and one of the twenty-two (22) communities located in the Yilo Krobo Municipality (between latitude 6000’N and 0030’N and longitude 0030’E - 1000’W) [Population & Housing Census, 2010]. Oterkpolu is about 1.5 km off the Koforidua-Asesewa main road. The estimated population of Oterkpolu is about 1.7% (1500 people) of the estimated 87,847 population of the Yilo Krobo Municipality (Population & Housing Census, 2010). The Municipality covers an estimated area of 1201 sq km and is predominantly rural (more than 67% of its population live in rural communities). The major economic activities in the Municipality are Agriculture, Trading and Small Scale University of Ghana http://ugspace.ug.edu.gh 37 Industrial activities (like Beads Making) [Population & Housing Census, District Analytical Report, (2010), Yilo Krobo Municipal]. Somanya is the administrative capital of the Yilo Krobo Municipality. The municipality shares boundaries (Fig 3.1) with New Juabeng and East Akim Municipalities to south- west, Fanteakwa to the west, Lower and Upper Manya Krobo to the north and east respectively, Akuapem North and Dangme West municipalities to the south (Population & Housing Census, District Analytical Report, (2010), Yilo Krobo Municipal). Fig 3.1 Map of study area showing the location of Oterkpolu and the limestone deposit University of Ghana http://ugspace.ug.edu.gh 38 The municipality is about 80% mountainous with numerous valleys. This is made up of the Akuapem Range stretching from the southwest to northeast across the municipality. The Togo series (including quartzites, phyllites, sandstones, phyllonites and sandy-shades) forms the rocks of the range peaking at an average height of between 300-500 meters above sea level (MOFA, 2015). 3.1.2 Oterkpolu Limestone Deposits The limestone deposit is located about 6.5 km east of Oterkpolu township (about 25 km from Koforidua, the Eastern regional capital). The limestone occurs within the arenaceous rocks of the Lower Voltaian range. The limestone is overlain by brown sandstone containing small iron-rich concretions which are weathered out to give a characteristic pitted surface with a purplish coloured transition zone at the base of the limestone (Atiemo, 2012). The rocks dip eastward into the hillside with local variation occurrences due to folding. Investigations by the Ghana Geological Survey have estimated the limestone reserve at Oterkpolu to be over 3.7 million tonnes (Kesse, 1985). 3.1.3 Commercial Mining of Oterkpolu Limestone After 1916, when the Buipe limestone deposit was discovered in Ghana, subsequent discoveries also led to that of Oterkpolu limestone (Pozzolanic material). This limestone mine went commercial in the year 2004 when Heidelberg Cement Group, producers of Ghana cement (GHACEM) set up a US$ 2million plant at Yongwase- Krobo in the Eastern region to produce cement from limestone (Business & Financial University of Ghana http://ugspace.ug.edu.gh 39 Times, BF&T, 2013). With the rapid expansion of Ghana’s economy with respect to the construction industry, GHACEM has contracted three mining companies (A. J. Fanj, Kamsad and Love) to mine the Limestone for the cement industry. 3.2 Reconnaissance Survey 3.2.1 Ethical Approval Ethical approval/approval to enter the Oterkpolu limestone concession was sought from and granted by the Management of the three limestone mining companies contracted by GHACEM to mine the limestone at Oterkpolu. 3.2.2 Site Visitation A site inspection was undertaken with the assistance of some Engineers and Geologist of the limestone mining companies (after ethical approval was granted). The visit to the limestone deposit was to identify the type of limestone available at the concession, to identify the equipment needed for sampling, and, to locate areas within the concession where samples will be collected. 3.2.3 Identification of Limestone during Site Visit Limestone is a sedimentary rock composed largely of the minerals, calcite (CaCO3) and aragonite. The minerals are different crystal forms of calcite. To identify limestone, the reaction between carbonate (CO32-) and dilute hydrochloric acid, (H+) used generally by Geologists in limestone identification was used. The evolution University of Ghana http://ugspace.ug.edu.gh 40 (effervescence) of the Carbon (IV) Oxide (CO2) gas (fizzy reaction) indicates the presence of calcite (CaCO3). CaCO3(s) + 2HCl(aq) → CaCl2(s) + H2O(l) + CO2(g) (3.1) Each fresh limestone samples from the different locations were first taken and tested using the reaction between carbonate and dilute acid {hydrochloric acid [10% (𝑣 𝑣⁄ ) HCl]. 3.3 Collection of Limestone The limestone samples were carefully identified and collected (Fig 3.2). Each limestone sample was labelled and first bagged in a High Density Polythene (HDPE) Woven Bag Sack with liners to prevent weathering. The limestone samples were then transported to the laboratories of the Ghana Atomic Energy Commission (GAEC) in Kwabenya, Accra. Fig 3.2 Packing of identified limestone samples for transportation to GAEC University of Ghana http://ugspace.ug.edu.gh 41 3.4 Sample Preparation and Analytical Methodology Development 3.4.1 General Overview of Experimental Work The experimental framework for the study is illustrated in Figure 3.3a (General Framework) and Figure 3.3b (scheme for development of water defluoridation technology). Fig 3.3a General Experimental Framework Radiological Risk/Safety [NORMs using γ-ray Spectrometry] Limestone Samples Preparation of Limestone Samples into suitable forms for analysis Mineral Composition [X-ray Powder Diffraction] Development of Defluoridation Technique [Batch Analysis] Mineralogical Composition [Petrographic Thin Section] Application of developed technique for the analysis of drinking water samples from affected communities [Column Analysis] University of Ghana http://ugspace.ug.edu.gh 42 Fig 3.3b Detailed work layout of the study Transportation of Limestone Samples to GAEC Radiological Safety Assessment, NORMs [γ-ray Spectrometry] Mining /Collection of mined Limestone Samples at Oterkpolu Grouping/Separation of Limestone Sample types based on colour Preparation of Limestone Samples for Petrographic Thin Sectioning (Mineral Composition) Breaking of Limestone Samples into smaller pieces (using hammer) Crushing broken Limestone Samples with Jaw Crusher Cutting of Limestone Sample into slabs using Slab Saw Sieving of crushed Limestone sample into different particle sizes i. 500 ˂ x ˂ 1000 (Coarse Sand) ii. 1000 ˂ x ˂ 2000 (Very Coarse Sand) iii. 2000 ˂ x ˂ 6350 (Very Fine Gravel – Fine Gravel) Pulverization of crushed Limestone Sample using Fritsch Pulverisette 2 Jaw Crusher Mineral composition using XRD Grinding of slab Limestone Sample using grinding wheels with abrasives Mineralogical Analysis using Petrographic Microscope Batch Analysis using NaF Adoption and application of optimized experimental conditions for further work Column Adsorption Experiment using real water samples collected from affected communities Collection of groundwater from affected communities Determination of Anions/Cations Column Adsorption Experiment Determination of Physico-Chemical Parameters Limestone Sample at Oterkpolu University of Ghana http://ugspace.ug.edu.gh 43 3.4.2 Sample Preparation 3.4.2.1 Mineralogy Using Petrographic Thin Section Instrumentation Slab saw, Grinding wheel, Microscope Glass Slide, Leica DM 750P Petrographic Microscope (Leica, Germany) Chemicals Canada balsam (a yellowish resin obtained from the balsam fir and used for mounting preparations on microscope slides) [Sinus Biochemistry & Electrophoresis GmbH, Germany] Principle In optical mineralogy and petrography, a thin section is a laboratory preparation of a rock, mineral, soil, pottery, bones, even metal sample for use with a polarizing Petrographic microscope, electron microscope and electron microprobe. A thin sliver of rock is cut from the sample with a slab saw and ground optically flat. It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick. Typically, quartz is used as the gauge to determine thickness as it is one of the most abundant minerals. When placed between two polarizing filters set at right angles to each other, the optical properties of the minerals in the thin section alter the colour and intensity of the light (as seen by the viewer). As different minerals have different optical properties, most rock forming minerals can be easily identified using the Michel-Lévy Interference Colour Chart (a tool used to identify minerals in Thin Section using a Petrographic Microscope). University of Ghana http://ugspace.ug.edu.gh 44 Experimental Procedure The limestone sample was cut into slabs with a slab saw (Fig 3.4a). The limestone slab was glued onto a microscope glass slide with Canada balsam (an epoxy and a hardener) (Fig 3.4b) for a firm grip. To ensure complete and even grinding, the specimen (limestone slab on the glass slide) was held on a grinding wheel (Fig 3.4c) and moved back and forth slowly with the right abrasive and grounded. The process was repeated with finer abrasives to get the right thickness (30 μm) for the specimen. It was then dried for about five (5) minutes and a cover slip was adhered to the surface of the grounded specimen to protect the section from damage; and also to increase the microscopic clarity. The specimen was placed and examined under a Leica DM 750P Petrographic Microscope (Fig 3.4d) to obtain the characteristics of the rock (which reflect its properties) and hence identify rock type with the aid of the Michel- Lévy Interference Colour Chart. Fig 3.4a Cutting of Limestone into slabs Fig 3.4b Canada Balsam University of Ghana http://ugspace.ug.edu.gh 45 Fig 3.4c Grinding wheel Fig 3.4d Petrographic Microscope 3.4.2.2 Determination of Mineral Composition Using X-Ray Diffraction (XRD) Instrumentation: Empyrean Series2 x-ray Diffractometer (XRD) [PANalytical, Netherlands], Fritsch Mortar Grinder Pulverisette 2 (Fritsch GmbH, Germany), Fritsch Jaw Crusher Pulverisette 2 (Fritsch GmbH, Germany), Rock-breaking hammer, Standard metal sample press Principle This analytical technique is used for phase identification of a crystalline material and can provide information on unit cell dimensions. The technique is based on constructive interference of monochromatic X-rays and a crystalline sample. The X- rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate, and directed towards the sample. The interaction of the incident rays with the samples produces constructive interference (and a diffracted ray) when conditions satisfy Bragg’s Law; Surface of Grinder wheel University of Ghana http://ugspace.ug.edu.gh 46 𝑛 ∙ λ= 2𝑑 sin 𝜃 (3.2) where, λ is the wavelength of the wave, θ is the angle between the incident rays and the surface of the crystal, d is the spacing between layers of the atom and n is an integer. This law relates the wavelength of the electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample. The diffracted X-rays are then detected, processed and counted. By scanning the sample through a range of 2θ angles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material. A conversion of the diffraction peaks to d-spacings allows identification of the mineral because each mineral has a set of unique d-spacings as compared with standard reference patterns. Experimental Procedure Limestone samples were broken into smaller fragments with a rock-breaking hammer, and further crushed with a Jaw Crusher Pulverisette 2 (Fig 3.5a). The crushed sample was further milled in Mortar Grinder Pulverisette 2 (Fig 3.5b). The powdered sample was passed through a 63 µm sieve to obtain a finely powdered homogenous limestone sample (Fig 3.5c). Aliquots of the finely powdered sample were used for the analysis. University of Ghana http://ugspace.ug.edu.gh 47 Fig 3.5a Crushing with Fritsch Fig 3.5b Milling with Fritsch Fig 3.5c Sieving of samples with a Pulverisette 2 Jaw Crusher Pulverisette 2 Mortar Grinder 63 µm mesh The powdered limestone samples (Fig 3.5d) were transformed into pellets using standard metal sample press (Fig 3.5e). The pellets were loaded into the sample exchanger and transferred to the x-ray Diffractometer (Fig 3.5f). Fig 3.5d Pulverized and Fig 3.5e Tools for transforming Fig 3.5f XRD Diffractometer homogenized samples powdered samples to pellets 3.4.2.3 Assessment of Radiological Risk Posed by Oterkpolu Limestone The radiological risk posed by the limestone was assessed through the determination of the Annual Effective Dose of the naturally-occurring radioactive materials (NORMs). This was achieved through measurement of γ-radiation activity of NORMs on HPGe γ-radiation detector, and hence calculation of Activity Concentration. The activity concentration obtained was used to calculate the Annual Dose Rate (ADR) and subsequently, the Annual Effective Dose (AED). Standard holder Stage Mortar (grinder) Back loader University of Ghana http://ugspace.ug.edu.gh 48 Calibration of γ-ray detector Prior to the analysis, energy and efficiency calibrations were performed to enable both qualitative and quantitative analysis of the samples. The detector system was calibrated using the multi-nuclide reference standard liquid solution (NW 146). The standard was measured in a 1.0 L Marinelli beaker using a counting time of 36000 seconds. The Standard Certificate (APPENDIX C9) was supplied by Czech Metrology Institute (Inspectorate for Ionizing Radiation, Canberra-Packed Central Europe, Wienersiedlung 6, Austria). Energy calibration The energy calibration was performed by matching the principal γ-rays in the spectrum of the standard reference material to the channel number of the spectrometer both manually or by software. The formulae relating the energy and the channel number is expressed as (3.3) where, E is the energy (keV), CN is the channel number for a given radionuclide, and A0 and A1 are calibration constants for a given geometry. A graph of energy against channel number is presented in Appendix G3. University of Ghana http://ugspace.ug.edu.gh 49 Efficiency calibration The efficiency calibration was performed by acquiring a spectrum of the standard until the count rate of total absorption could be calculated with a statistical uncertainly of <1% at a confidence level of 95%. The net count rate was determined at the photo peaks for all the energies to be used for the determination of the efficiency of the calibration standard at the time of measurement. The efficiency at each energy level was plotted as a function of the peak energy and extrapolated to determine the efficiencies at other peak energies for the measurement geometry used. The efficiency was then related to the count rate and the activity of the standard calculated using Equation 3.4 (Gilmore and Hemingway, 1995). 𝜼 = 𝑵 Pγ ×Tc ×A (3.4) where, η is the efficiency of the detector; N is the total count under a photo peak; Pγ is the gamma ray emission probability for the energy, in a peak range; A is the activity of the calibration standard for a given radionuclide in Bq at the time of measurement; and, Tc is the counting time. The efficiency is related to the energy by the expression. 𝑰𝒏(𝑬) = a0 + a1𝑰𝒏E1 + a2𝑰𝒏E2 (3.5) University of Ghana http://ugspace.ug.edu.gh 50 where, a0, a1 and a2 are calibration constants for a given geometry. The efficiency calibration curve is presented in Appendix G4. From the efficiency calibration curve, the following expression was obtained using a first order polynomial: 𝐈𝐧𝛈 = 𝟏. 𝟐𝟑𝟗 – 𝟎. 𝟗𝟗𝟓𝐈𝐧𝐄𝛄 (3.6) For Eγ > 100 keV Experimental procedure Sample Preparation One (1) kg each of the sieved limestone samples were transferred into 1 litre Marinelli beakers. The beakers were sealed using a paper tape to prevent the escape of gaseous radionuclides in the sample. They are then labelled appropriately for activity concentration measurement as shown in Figure 3.6a. This was left for a period of 30 days to attain secular equilibrium between the long-lived parent nuclides of 226Ra (238U) and 232Th, and their short-lived daughters (Darko & Faanu, 2007; Matiullah et al., 2004; Merdanoglu & Altinsoy, 2006). The method of γ-analysis adopted for this work is by using High Purity Germanium (HPGe) Gamma-ray detector as shown in Figure 3.6b. University of Ghana http://ugspace.ug.edu.gh 51 Fig 3.6a Packaging of Limestone Sample in a Fig 3.6b HPGe Gamma Detector for NORMs 1 L Marinelli beaker measurement γ-radiation Measurement on the HPGe Detector The γ-radiation intensity of the limestone samples were measured on a coaxial HPGe semiconductor γ-ray detector (Fig 3.6b). The 1 kg finely powdered limestone sample contained in the 1 L Marinelli polyethylene beaker was placed on the coaxial HPGe γ-ray detector and the γ- radiation intensity of NORMs contained in the limestone measured for 36,000 seconds (10 hours). The γ-radiation activity of the uranium-series were determined using the γ-ray emissions of 214Pb at 351.9 keV (35.8%) and 214Bi at 609.3 keV (44.8%) for 226Ra. For the 232Th-series, the γ-ray emissions of 228Ac at 911 keV (26.6%), 212Pb at 238.6 keV (43.3%) and 208Tl at 583 keV (30.1%) were used. The γ-radiation activity of 40K was determined directly from its γ-ray emission line at 1460.8 keV (10.7%). Computer HPGe γ-ray detector Dewar flask with Liq. N2 University of Ghana http://ugspace.ug.edu.gh 52 Calculation of Activity Concentration The specific activity concentrations (Asp) of 232U, 232Th and 40K in Bq kg-1 for the limestone samples (APPENDIX C1-C9) were determined using the Equation 3.7 [Awudu et al., (2010)]: Asp = Nsam Pγ·𝜼·Tc· M (3.7) where, Nsam - net counts of the radionuclide in the sample Pγ - gamma ray emission probability (gamma yield) η - total counting efficiency of the detector system Tc - sample counting time M - mass of sample (kg) or volume (L) Calculation of Absorbed Dose Rate (ADR) From the mean specific concentrations of 232U, 232Th and 40K , the dose rate was calculated using the relation from Beck et al., (1992); 𝐴𝑅𝐷 = 0.417𝐶𝑈 + 0.462𝐶𝑇ℎ + 0.604𝐶𝐾 (3.8) where, CU, CTh and CK are the specific concentrations of 238U, 232Th and 40K in Bq/kg respectively. University of Ghana http://ugspace.ug.edu.gh 53 Calculation of Annual Effective Dose (AED) The Annual Effective Dose due to the absorbed dose rate was applied using the conversion factor of 0.7 Sv/Gy (UNSCEAR, 2000); 𝑨𝑬𝑫 = 𝑨𝑹𝑫 · 𝟖𝟕𝟔𝟎𝒉𝒓 𝒚𝒓 · 𝟎. 𝟐 · 𝟎. 𝟕𝑺𝒗 𝑮𝒚 · 𝟏𝟎−𝟔 (3.9) where, 0.2 is the outdoor occupancy proposed by UNSCEAR, (2000) ; and, 0.7 Sv/Gy is the dose conversion factor. 3.5 Development of Limestone Defluoridation Technique using Batch Analysis 3.5.1 Preparation of Limestone Samples Instrumentation Jaw Crusher Pulverisette 2 (Fritsch GmbH, Germany), Retsch AS 200 Vibratory Sieve Shaker (Retsch GmbH, Germany) Experimental Procedure Limestone samples were broken into smaller fragments (Suresh and Dutta, 2010; Beraki, 2014) with the Jaw Crusher Pulverisette 2. The crushed limestone samples were then loaded into arranged selected sieves in order of increasing sizes (500, 1000, 2000 and 6350 µm). The loaded sieves were clamped on the Retsch AS 200 Vibratory Sieve Shaker and agitated for about 15 minutes (Fig 3.7a). The different sieved limestone particles (Fig 3.7b) were stored separately in hermitically-closed polythene bags and labelled. To avoid cross contaminating of one sample with the other, the sieves were washed, dried and cleaned with acetone after sieving each sample. University of Ghana http://ugspace.ug.edu.gh 54 Fig 3.7a Shaking sample with Retsch AS 200 Fig 3.7b Sieved limestone Samples Vibratory Shaker 3.5.2 Batch Adsorption Experiment Instrumentation A DIONEX ICS-90 Ion Chromatographic System was used for fluoride content determination in Batch Adsorption experiments; as well as fluoride, chloride, nitrate, sulphate and phosphate in the Column Adsorption experiment. The chromatographic system consists of a DIONEX AMMS 300 (4 - mm) Anion Micro-Membrane Suppressor, a DIONEX IonPac AS14A-5 µm Analytical Column (3 × 150 mm), a DIONEX IonPac AG14A-5 µm Guard Column (3 × 30 mm), and an ICS-900 DS 5 Detection Stabilizer Acquisition and quantification of the chromatographic spectrum was achieved using the DIONEX CHROMELEON Chromatographic Data Management System Software (Thermo Scientific, USA). Chromatographic Solutions and Standards Eluent solution: mixture of 0.16 M Na2CO3 and 0.02 M NaHCO3 Regenerant solution: 4 M H2SO4 Fig 3.8a Eluent standard solution Fig 3.8b Regenerant standard solution Metal sieves Vibratory Sieve Shaker University of Ghana http://ugspace.ug.edu.gh 55 Standard: Dionex Seven Anion Standard II (Thermo Fisher Scientific, USA) containing 20 mg/L, with the following composition (99.9 % H2O, 20 mg/L F-, 100 mg/L Cl-, 100mg/L NO2-, 100 mg/L Br-, 100 mg/L NO3-, 200 mg/L PO32-, and 100 mg/L SO42-) Operating Conditions The compressor uses air (Nitrogen gas) drawn from the ambient surroundings. The flow rates of Eluent and the Regenerant solution are 0.5mL/min respectively. Calibration of Chromatographic System Using a pre-washed syringe [1 mL Norm Ject syringe (DIN/EN/ISO 7886-1)], calibration standards of concentrations 5, 10, 15 and 20 mg/L were each injected into the IC and allowed to flow at a rate of 0.5 mL/min to calibrate the ICS-90. The standards were prepared from Dionex Seven Anion Standard II (Thermo Fisher Scientific, USA) containing 20 mg/L, having the following composition (99.9 % H2O, 20 mg/L F-, 100 mg/L Cl-, 100 mg/L NO2-, 100 mg/L Br-, 100 mg/L NO3-, 200 mg/L PO32-, and 100 mg/L SO42-). After the last peak (SO42–) has appeared and the conductivity signal has returned to the base line, water sample were then injected. The Eluent used for the analyses was a solution of 0.16 M Na2CO3 and 0.02 M NaHCO3, whiles the anion Regenerant used was 4 M H2SO4. University of Ghana http://ugspace.ug.edu.gh 56 Apparatus/Materials Measuring cylinder (50 and 100 mL), Magnetic stirrer (Eisco EI 0112M, India), Beakers, Sampling bottles, 1 mL Syringe (Ningbo Clan Medical Instruments Co, Ltd, India), PTFE Syringe Filter-0.45 µm (Filter-Lab, UK), Volumetric flask (1000 and 100 cm3), Mettler AB204-S analytical balance (Mettler Toledo, ) Fluoride Standards A Stock solution containing 100 mg/L was prepared by dissolving 0.221 g of anhydrous NaF and diluting to volume (1000 mL) with deionised water. Working standards of concentrations 1, 5 and 10 mg/L were prepared by appropriate dilution of the stock (detailed calculation for the preparation of the stock and working solutions is presented in APPENDIX E1 and E2). The concentrations of the prepared solutions (stock and dilute) were ascertained using the DIONEX ICS-90 Ion Chromatographic (IC) System. The results are presented in Table 3.1. Table 3.1 Concentrations (prepared and measured) of standard solutions using IC Type of standard Concentration (mg F-/L) Prepared Measured (Range) [No. of determinations] Stock 100.00 100.83 ± 0.39 (100.08 - 101.13) [5] Working 1 1.06 ± 0.05 (0.99 – 1.10) [3] 5 5.00 ± 0.03 (4.98 – 5.05) [3] 10 10.06 ± 0.95 (9.95 – 10.16) [3] University of Ghana http://ugspace.ug.edu.gh 57 Experimental Procedure About 10, 50 and 100 grams aliquots of the raw crushed limestone were for each of the three (3) grain sizes (500-1000, 1000-2000 and 2000-6350 µm) were respectively weighed into 250 mL beakers using a Mettler AB204-S analytical balance (Fig 3.9a). Each limestone aliquot was mixed with 100 mL of 1, 5 and 10 mgF-/L (Anhydrous Sodium Fluoride (NaF) solution) respectively. This was followed by stirring magnetically for about 90 minutes with an Eisco EI 0112M Magnetic Stirrer (Fig 3.9b). Aliquots of the mixture were taken at 15 minutes intervals and the residual fluoride concentration measured using the DIONEX ICS-90 Ion Chromatographic System (3.9c). A blank was prepared by mixing 10 g limestone with 100 mL of distilled water and agitating it magnetically. Fig 3.9a Weighing of sample Fig 3.9b Magnetic stirrer of Fig 3.9c IC for F- measurement mixture Injection Port Gas Inlet Regulator Eluent Reservoir Regenerant Reservoir University of Ghana http://ugspace.ug.edu.gh 58 The defluoridation efficiency of the limestone sample was determined by measuring the initial and residual fluoride concentrations in the various aliquots taken and calculated using equations: % Adsorption = 𝐶𝑜−𝐶𝑡 𝐶𝑜 × 100 (3.10) Adsorption Capacity = 𝐶𝑜−𝐶𝑡 𝑀 × V (3.11) where, Co = initial fluoride concentration Ct = residual fluoride concentration M = mass of adsorbent used V = volume of fluoride used in Batch experiment 3.6 Application of Developed Technique The developed defluoridation technique was applied to defluoridate water from Bongo in the Upper region of Ghana, using the Column Adsorption experiment. 3.6.1 Collection of Water Samples from Bongo District Prior to the collection of the water samples, the sampling bottles (330 mL) were conditioned by first treating with 10% (v/v) HNO3 solution for 48 hours, followed by thorough rinsing with double-distilled water (APHA, 1998). Water samples were collected from five (5) communities (Bongo-Namoa, Bongo- Navorogo, Bongo-Anafobiisi, Bongo-Zuruyi, and Bongo-Soe) in the Bongo district of the Upper East region. A total of 10 samples (from uncapped wells) were collected in University of Ghana http://ugspace.ug.edu.gh 59 March 2016 (Fig. 3.10). At each sampling point, three replicate samples were taken. Of the three replicate samples, one sample was acidified with 10% HNO3 for heavy metals determination. This was done to preserve the water samples and to dissolve the particulate metals into the solution (APHA, 1992). Fig 3.10 Uncapped boreholes at two affected communities in the Bongo District At each sampling point, just before samples were collected from the borehole, the water in the borehole was purged. This is because a fresh water sample is needed to accurately assess groundwater quality. Water standing in a well for a period of time undergoes changes that can affect and alter the water quality. Example of these changes includes temperature, oxidation, biological activity, precipitation of metals and reactions with the well casing. These changes can impact several parameters such as pH, alkalinity, TDS and concentration of metal (USEPA, 1996; Koterba et al., 1995). After filling the sampling container with the water sample, the container was securely capped, labelled and kept in a thermo-insulated container with some ice packs. The collected samples were transported overnight courier to the laboratories of the Ghana Atomic Energy Commission located at Kwabenya, Accra, for analysis. University of Ghana http://ugspace.ug.edu.gh 60 3.6.2 Determination of Physico-chemical Parameters Six (6) physico-chemical parameters, namely pH, Electrical Conductivity (EC), Salinity, Colour, Turbidity and Total Dissolved Solids (TDS) were determined. 3.6.2.1. Determination of pH The pH of the water samples was determined using the pH 3110 SET 1 2AA111 multi-fractional meter [Wissenschaftlich Technische Werkstatten (WTW) Germany]. The pH meter was first calibrated using two standard buffer solutions of pH 4.01 and 7.01, respectively. After the calibration, the pH meter was used to determine the pH of the water samples. About 100 mL of the water sample was transferred into a 250 mL beaker and thoroughly homogenized by swirling. The sensing electrode of the pH meter was placed in the water sample for about five (5) minutes for the reading to stabilize. The pH of the water was then recorded. The calibration of the meter was verified after measuring every four samples. After each reading, the electrode is rinsed with double distilled water and a small portion of the next sample to be determined. 3.6.2.2 Determination of Electrical conductivity (EC), Total Dissolved Solid (TDS), Turbidity, Colour and Salinity Instrument: HI 991301 pH/EC/TDS/Temperature meters (Hanna Instruments, USA ) Reagent: 0.01 M KCl University of Ghana http://ugspace.ug.edu.gh 61 Experimental Procedure The Hanna HI 991301 multi-functional conductivity meter was used to determine EC, TDS, Turbidity, Colour and Salinity of the water samples. Prior to measurement, the meter was calibrated using a standard reference solution of 0.01 M KCl solution of known conductivity (1412 µS/cm). The electrode was rinsed in distilled water followed by measurement of the parameters in the water sample. The electrode was dipped into the sample and was slowly moved circularly for a minute until digital readout was stabilised. 3.6.3 Column Adsorption Experiments Apparatus/Materials In-house designed mini-column glass bed of diameter 4 cm and varying heights of 20, 30 and 40 cm. Experimental procedure The mini-column glass beds were clamped and loaded with the selected limestone sample (R102) of grain size 1000-2000 µm (Fig 3.11a). The bed column was supported and closed at the outlet with cotton wool to prevent the flow of the adsorbent together with the effluent or filtrate. The bed was rinsed with distilled water and left overnight to ensure a closely packed arrangement of the particles. The Bongo water sample was poured onto the packed limestone in the fixed mini-column bed. Aliquots of filtrate solutions were taken from the outlet of each bed at 15 minutes interval for 90 minutes (Fig. 3.11b). The residual University of Ghana http://ugspace.ug.edu.gh 62 fluoride concentration was determined using the DIONEX ICS-90 Ion Chromatographic System. Fig. 3.11a Mini-Column bed filled Fig 3.11b Aliquots taken from the different with adsorbents mini-column beds 3.6.4 Determination of Cations The VARIAN AA 250 Fast Sequential (FS) Atomic Absorption Spectrometer equipped with deuterium background corrector was used in the determination of cations in the water samples. The instrument consists of a light source (hollow- cathode lamp), a flame atomizer system (Air-Acetylene), monochromator or filter and adjustable slit (means of isolating an absorption line) and a photoelectric detector with its associated electronic amplifying and measuring equipment. Water samples meant for cation analysis were acidified with 3.0 mL (10% v/v) concentrated HNO3. This was done to preserve the water samples and to dissolve the particulate metals into the solution (APHA, 1992). Digestion of Water Samples The Reagents used for the digestion of water samples are: 36% (w/v) HCl (AnalaR grade) and 70% (w/v) HNO3 (AnalaR grade) Packed limestone beds University of Ghana http://ugspace.ug.edu.gh 63 The water samples were digested using the hot plate method. About 40 mL of the water sample was transferred into a borosilicate glass beaker, followed by the addition of 5 mL of aqua regia (4.5 mL HCl to 0.5 mL HNO3). The mixture were covered with clean film and placed on the hot plate and digested for 3 hours at a temperature of about 45 oC (Fig 3.12a and 3.12b). The digested samples were cooled, filtered and diluted with double distilled water nominal volume of 30 mL. It is then transferred into labelled test tubes and analyzed using the VARIAN 240FS atomic absorption spectrometer. Fig 3.12a Samples being prepared for digestion Fig 3.12b Samples on a hot plate during digestion 3.6.4.1 Magnesium (Mg2+) Magnesium (Mg2+) levels in the water samples were determined using the VARIAN AA 250 Fast Sequential (FS) Atomic Absorption Spectrometer. Reagents Lanthanum solution was prepared by dissolving 11.730 g of La2O3 in a minimum volume of 10 % HNO3 and diluted with distilled water to 1000 mL. This reagent serves as ion suppressant. University of Ghana http://ugspace.ug.edu.gh 64 Experimental Procedure Conditions associated with the operation of the AAS used for analysing Mg2+ in the samples are as follows:  air-acetylene flame atomizer; air flow rate was 13.50 L/min and acetylene flow rate was 2.00 L/min  Hollow cathode lamp current and wavelength were 4 mA and 285.2 nm respectively  Slit width was 0.1 nm Magnesium calibration standards (0.00, 0.10, 0.20 and 0.50 mg/L) was prepared by appropriate diluting a commercially-available magnesium stock solution. The prepared solution was used to calibrate the instrument (calibration graph in APPENDIX G1). This was followed by sample analysis. To prepare the samples for analysis, 1 mL of the water sample was transferred into a test tube, followed by the addition of 9 mL lanthanum solution (100 mg/L) was added and thoroughly homogenized by shaking. The prepared samples were then aspirated into the AAS. After every 10 readings a standard (magnesium calibration standard solution) is aspirated as a quality control measure. Calculation [Mg2+] in mg/L in the water samples were calculated from direct reference to the calibration curve according to the equation: [Mg2+] (3.12) University of Ghana http://ugspace.ug.edu.gh 65 where, D is the dilution factor ratio 3.6.4.2 Determination of As by HG-AAS Reagents: Hydrochloric acid [AnalaR grade, 50% (v/v)], Sodium borohydride solution [AnalaR grade, 0.5 % (m/v) in 0.5 % (w/v) NaOH), Pre-reducing solution [AnalaR grade, 10 % (w/v) potassium iodide + 10 % (w/v) L-ascorbic acid], and arsenic standard (1000 mg/L) Prior to analysis of the water samples for arsenic, As5+ was reduced to As3+. This was achieved by the addition of 4 mL of freshly prepared 5 M KI to the digested sample. (3.13) Hydride generation The continuous flow approach was used to merge sample solution and reagents. The sample solution of flow rate 0.1 mL/s was mixed with both HCl and NaBH4 in a polyetheretherketone (PEEK) cross connector and pumped into a reaction coil. During the mixing, arsenic hydride (AsH3) and considerably hydrogen gas (H2) are produced. (3.14) (3.15) The gaseous AsH3 and H2 generated were separated from the liquid phase and transferred with a flow argon gas and dried by a stream of nitrogen gas. The liquid goes to waste and the gaseous hydride and hydrogen were swept out of the vapour generation vessel into the atomisation system of the AAS. University of Ghana http://ugspace.ug.edu.gh 66 Calibration Calibration standards (0.02, 0.04, 0.08 and o.10 mg/L) were prepared by appropriate dilution of the commercially-available stock As solution. A calibration graph (absorbance versus concentration of calibrants) was plotted (APPENDIX G2). This was followed by aspirating the KI reduced samples into the AAS. Calculation The concentration of As in each water sample obtained from the equation of the regression line of the calibration curve was used to calculate the final concentration of the water samples according the equation; 𝐹𝑖𝑛𝑎𝑙 𝑐𝑜𝑛𝑐. (𝑚𝑔 𝐿⁄ ) = 𝐶𝑜𝑛𝑐.𝐴𝐴𝑆×𝐷𝑓×𝑁𝑜𝑚𝑖𝑛𝑎𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 𝑆𝑎𝑚𝑝𝑙𝑒 𝑤𝑒𝑖𝑔ℎ𝑡(𝑔) (3.16) where, 𝐷𝑓 is dilution factor. 3.6.5 Determination of Anions 3.6.5.1 Determination of Fluoride (F-), Chloride (Cl-), Phosphate (PO43-), sulphate (SO42-) and Nitrate (NO3-) using ICS-90 Chromatographic System The set-up and experimental conditions for the ICS-90 Chromatographic System was the same as described during Batch Adsorption Experiment in section 3.5.2. University of Ghana http://ugspace.ug.edu.gh 67 Experimental Procedure Sample analysis After calibration, samples were injected into the IC using a 1 mL Norm Ject syringe (DIN/EN/ISO 7886-1). During the injection, uniformity in the injection process is required to give a pulse-free flow. After five (5) to ten (10) sample injections, distilled water was used to flash the system. The chromatographic spectrum obtained showed the peaks for each anion (Fig. 3.13) Fig 3.13 Example of a Chromatographic spectrum obtained University of Ghana http://ugspace.ug.edu.gh 68 CHAPTER FOUR RESULTS AND DISCUSSION The results obtained from the study are presented and discussed in this Chapter. The discussion is supported by presentation of some of the results in Tables and Figures. 4.1 Petrographic Thin Section The results of the Petrographic Thin Section conducted on the eight (8) limestone samples from Oterkpolu is presented in Table 4.1. Table 4.1: Percentage composition of mineralogical content of selected samples Sample XRD (%) PTS (%) EKL-R102 Calcite (83), SiO2 (6), Serandite (11) Calcite (96), Quartz (4) EKL-D01 Calcite (68), Dolomite (22), SiO2 (10) Calcite (85), Quartz (15) EKA-R02 Calcite (95), SiO2 (5) Calcite (71), Quartz (21) EKA-R01 Calcite (19), Dolomite (22), SiO2 (17) Calcite (95), Quartz (5) {K, Na, Al, Fe, Mg, Ti} (42) EKL-Y03 Calcite (17), SiO2 (16), Muscovite (23) Calcite (90), Quartz (10) Ankerite (44) EKA-Y04 Dolomite (57), SiO2 (30), Ankarite (7) Calcite (95), Quartz (5) Muscovite (6) EKA-B01 Calcite (13), Dolomite (54), SiO2 (8) Calcite (98), Quartz (2) Diopside (25) EKA-Bk03 Dolomite (98), SiO2 (2) Calcite (95), Quartz (5) EKL-Y01 Calcite (28), Dolomite (10), SiO2 (24) Nil Muscovite (38) University of Ghana http://ugspace.ug.edu.gh 69 From the Petrographic Thin Section (PTS) and X-Ray Diffraction analysis, two samples (EKL-R102 and EKL-D01) were selected for the Batch Adsorption Experiment. The selection was based on the high percentage of Calcite and Dolomite mineral content in both analysis and the abundance of the sample. The Calcite had been the major compound (analyte of interest) for the reaction with the fluoride ions. 4.1.1 Sample EKL R102 Hand Sample The rock is grey in colour and fined grained and layered. Iron (Fe), probably present as siderite gives some of the layers a reddish colour. The specimen fizzed with dilute hydrochloric acid indicating the presence of calcite. Thin Section The photomicrograph of the sample (Fig 4.1) revealed the dominance of fined grained calcite with angular quartz grains in the minority. Iron rich bands can evident. The iron here may exist in the form of siderite. The sample has fractures indicating that, the sample seems to have undergone deformation or alteration. 4.1.2 Sample EKL D01 Hand Sample This sample is grey in colour and finely grained. It is also massive and lacks lamination. Calcite present in the sample fizzes with dilute hydrochloric acid. Crystalline grains of quartz are also visible in hand sample. University of Ghana http://ugspace.ug.edu.gh 70 Thin Section The photomicrograph of the sample (Fig 4.2) consists of two layers. One layer contains very fine grains of calcite with a few quartz grains. The other layer has bigger, angular grains of quartz. This layer is still dominated by calcite. This layering could have formed due to an alternation in the phases of deposition of the silicilastic sediments and calcite which make up the rock. The sample has no fractures and does not seem to have undergone deformation or alteration. Fig 4.1: Photomicrograph of sample EKL R102 Fig 4.2: Photomicrograph of sample EKL D01 4.2 XRD Analysis In order to determine the mineralogical composition of Oterkpolu limestone, few grams of the different samples were taken and quantitatively analysed by X-ray Diffraction using Diffractometer with copper (Cu) as the anode material, an Alpha 1 wavelength (λ) of “1.54060”, Alpha 2 wavelength of “1.54443” and K-Beta wavelength of “1.39225”. From the analysis, two samples (EKL-R102 and EKL-D01) were selected due to the following criteria: Iron rich band Fractures Calcite Quartz Fined Grained Calcite Layer Quartz Rich Layer University of Ghana http://ugspace.ug.edu.gh 71 a. High percentage of calcite content for an efficient adsorption reaction with fluoride. b. The abundance of the particular type of sample present. 4.2.1 Limestone Samples EKL- R102 and EKL-D01 Fig 4.3 Diffractogram of limestone sample EKL-R102 (A) and EKL-D01 (B) From the analysis, the sample EKL-R102 is made up of two main minerals; calcium carbonate (calcite) and silicon oxide (quartz). The calcite and silicon oxide constitutes 95% and 5% respectively as per the phase identification of Oterkpolu limestone sample. The highest peak at 2theta (29.4456) was 10343.67 (Fig. 4.3A). On the other hand, sample EKL-D01 is made up of 68% Calcium Carbonate (Calcite), 22% Dolomite (Calcium Magnesium Carbonate) and 10% Silicon Oxide. Its highest peak at 2 theta (2θ) [29.4406] was 8791.41 (Fig. 4.3B).The full peak list of the analysis is presented in Appendix A6 and A9 respectively. 4.3 Radiological Safety of the Limestone Samples 4.3.1 Activity Concentration of Naturally Occurring Radionuclides in Limestone Sample In all the samples from Oterkpolu, the Activity Concentration of K-40 was higher than Th-232 and U-238 (Fig. 4.4). Limestone sample EKA-Bk03 was the only sample A B University of Ghana http://ugspace.ug.edu.gh 72 with Activity Concentration of K-40 as low as 5.42 as compared to the highest concentration of 49.40 in EKL-R102. Fig 4.4 Plot of Activity Concentration against limestone Type. The mean activity concentration of U-238, Th-232 and K-40 of the different limestone are 2.0 ± 1.5, 1.7 ± 1 and 21.9 ± 13.4 respectively. The average values of concentrations of 238U, 232Th and 40K in soils worldwide in Bq/kg are 33, 45 and 420 respectively (UNSCEAR, 2000). This indicates that the Activity Concentrations of Oterkpolu limestone is less than the stated values above and the average concentrations reported in similar studies in other parts of the world (India, Serbia, Belgium and Turkey) [Table 4.2]. 0 0.5 1 1.5 2 2.5 3 A ct iv it y C o n ce n tr at io n ( kb /B q ) Limestone Samples Activity Concentrations of the different Oterkpolu Limestone Samples U-238 Series Th-232 Series K-40 Series University of Ghana http://ugspace.ug.edu.gh 73 Table 4.2: Comparison of Reported Activity Concentrations with the Present Study Country Activity Concentration (Bq/kg) Nature of sample Reference 238U 232Th 40K Ghana ? ? ? Limestone samples This study from Oterkpolu Ghana 7.3 6.9 379.9 Sediment from Tono Agalga, 2012 Irrigation Dam India 7.3 46.8 384.03 Sediments from Ramasamy et Ponnaiyar River al., 2009 Serbia 42 36 445 Sediments from Krmar et al. 2009 Danube Turkey 39 38 573 Sediments from Kurnaz et al., 2007 Firtina valley The calculated Annual Effective Dose (AED) of the selected samples (EKL-R102 and D01) are 0.03 and 0.01 mSv/yr respectively. Notwithstanding, the mean Annual Effective Dose of limestone from Oterkpolu is estimated at 0.013 mSv/yr. This value is lower than the recommended 0.40 mSv/yr according to UNSCEAR, 2000. This means that, the samples are radiologically safe. Both internal and external hazard indices gave mean values of 0.01 and 0.02 respectively. Exposures at or below the reference level (HI = 1) indicates that no adverse human health effects (non cancer) are expected to occur. Table 4.3 gives a detailed analysis of the various samples. University of Ghana http://ugspace.ug.edu.gh 74 Table 4.3: Absorbed Dose and Radioactivity Indices Associated with Oterkpolu Limestone Samples Sample ID ADR(Gy/hr) Hazard Index × 𝟏𝟎−𝟑 AED(mSv/yr) × 𝟏𝟎−𝟑 238U/232Th Ratio Hin Hex EKA-B01 9.0514 19.442 14.361 11.101 0.777 EKA-Bk03 2.4736 3.631 2.379 3.034 0.000 EKA-R01 13.7347 12.748 11.399 16.844 1.866 EKA-R02 6.14168 6.629 5.591 7.532 1.156 EKA-Y04 8.1668 21.452 15.784 10.016 0.874 EKL-Y03 14.7535 19.704 16.054 18.094 1.115 EKL-D01 9.8808 46.622 32.326 12.118 0.761 EKL-R102 21.8746 20.360 18.226 26.827 1.910 MINIMUM 2.4736 3.631 2.379 3.034 0.000 MAXIMUM 21.8746 46.622 32.326 26.827 1.910 MEAN 10.7596 18.824 14.515 13.196 1.057 STD. DEV. 5.5761 12.245 8.453 6.839 0.582 4.4 Batch Adsorption Experiment 4.4.1 General Procedure Each of the two crushed limestone samples (EKL-R102 & EKL-D01) of grain sizes (500-1000 µm, 1000-2000 µm and 2000-6350 µm) and masses (10 g, 50 g and 100 g) were each combined with 100 mL of approximately 1, 5 and 10 mg/L anhydrous Sodium Fluoride (NaF) solution. Each NaF-Limestone mixture was agitated magnetically with Eisco E0112M Magnetic Stirrer for 90 minutes and aliquots of the University of Ghana http://ugspace.ug.edu.gh 75 mixture were taken every 15 minutes and the residual fluoride concentration determined with DIONEX ICS-90 Ion Chromatographic System. Before the agitation of the mixture, the pH of the NaF-Limestone mixture was determined. A blank of limestone-distilled water mixture was also determined for each batch experiment. [Let sample EKL-R102 = A and sample EKL-D01 = B] 4.4.2 Effect of Varying Residence Time on Residual Fluoride Adsorption in 1 mg/L Fluoride Solution Batch Adsorption Experiment 1 A 10 g mass each of the two limestone samples (A & B) of grain size 500-1000 µm were mixed with 100 mL of 1 mg/L NaF solution. The pH of the each mixture (7.78 and 9.42 respectively) was recorded. A graph of residual fluoride concentration with time for the two limestone type (Fig. 4.5) was plotted. Fig 4.5 Plot of Residual F- concentration against Time for 10 g mass (500-1000 μm) samples in 1 mg/L NaF Sample A recorded a maximum residual fluoride concentration of 0.3124 mg/L (71.53%) at the 45th minute of the 90 minute duration, while sample B gave a 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 76 maximum residual fluoride concentration of 0.4721 mg/L (53.85%) at the 60th minute (Fig. 4.5). Batch Adsorption Experiment 2 A 50 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 1 mg/L NaF solution. The pH of the mixtures was 7.80 and 9.47 respectively. A graph of residual fluoride concentration with time (Fig 4.6) for the two limestone type was plotted. Fig 4.6 Plot of Residual F- concentration against Time for 50 g mass (500-1000 μm) sample in 1 mg/L NaF Both samples attained equilibrium at the 60th minute but with different residual fluoride concentrations (Fig. 4.6). Samples A and B recorded residual fluoride concentrations of 0.3487 mg/L (68.22%) and 0.5298 (48.21%) respectively. Fluoride removal was detected to increase with increasing contact time to a point when equilibrium was attained using crushed limestone and fluoride solutions acidified with acetic acid and the other with citric acid (Suresh and Dutta, 2010). 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 77 Batch Adsorption Experiment 3 A 100 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 1 mg/L NaF solution. The Ph of the mixtures was 7.80 and 9.50 respectively. Fig 4.7 Plot of Residual F- concentration against Time for 100 g mass (500-1000 μm) samples in 1 mg/L NaF Sample A attained equilibrium at the 60th minute and sample B attained its equilibrium at the 75th minute (Fig. 4.7). The residual fluoride concentrations at these equilibrium points are 0.7623 mg/L (30.53%) for sample A and 0.7201 (29.61%) for sample B. Batch Adsorption Experiment 4 A 10 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 1 mg/L NaF solution. The pH of the mixtures was 7.65 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 78 and 9.38 respectively. A graph of residual fluoride concentration with time (Fig.4.8) for the two limestone type is illustrated below. Fig 4.8 Plot of Residual F- concentration against Time for 10 g mass (1000-2000 μm) samples in 1 mg/L NaF Both samples attained equilibrium at the 60th minute but with different residual fluoride concentrations (Fig. 4.8). Samples A and B recorded residual fluoride concentrations of 0.2521 mg/L (77.03%) and 0.4329 (57.68%) respectively. The effect of contact time on fluoride adsorption was investigated at different doses and particle size of iron ore. It came out that, the amount of fluoride adsorbed increases with time and reached its steady state in 120 min at which the maximum adsorption efficiency (86%) and maximum adsorption capacity (1.72 mg/g) were achieved (Kebede et al., 2014). Batch Adsorption Experiment 5 A 50 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 1 mg/L NaF solution. The pH of the mixtures was 7.70 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 79 and 9.44 respectively. A graph of residual fluoride concentration with time (Fig. 4.9) for the two limestone type is shown below. Fig 4.9 Plot of Residual F- concentration against Time for 50 g mass (1000-2000 μm) samples in 1 mg/L NaF Sample A recorded a maximum residual fluoride concentration of 0.4502 mg/L (58.97%) at the 45th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 0.61531 mg/L (39.85%) at the 60th minute (Fig. 4.9). similar work was done on the effect of contact time on fluoride removal from water using aluminium containing compounds (Karthikeyan and Elango, 2007). The result of the equilibrium studies showed that, the removal of fluoride ions increased with time up to 40 min, and after which the increase in agitation time did not alter the fluoride ion uptake due to the attainment of equilibrium. Batch Adsorption Experiment 6 A plot of residual fluoride concentration with time (Fig. 4.10) for 100 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm mixed with 100 mL of 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 80 1 mg/L NaF solution is shown below. The pH of the mixtures was 7.79 and 9.50 respectively. Fig 4.10 Plot of Residual F- concentration against Time for 100 g mass (1000-2000 μm) samples in 1 mg/L NaF Sample A recorded a maximum residual fluoride concentration of 0.5983 mg/L (45.48%) at the 45th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 0.641 mg/L (37.34%) at the 60th minute (Fig. 4.10). Batch Adsorption Experiment 7 A plot of graph (Fig. 4.11) shows a 10 g mass each of the two limestone (A & B) samples of grain size 2000-6350 µm mixed with 100 mL of 1 mg/L NaF solution. The pH of the mixtures was 7.73 and 9.39 respectively. 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 81 Fig 4.11 Plot of Residual F- concentration against Time for 10 g mass (2000-6350 μm) samples in 1 mg/L NaF Sample A shows an appreciable increase in residual fluoride concentration until the 60th minute where the concentration became constant. Equilibrium was not established in this respect (Fig. 4.11). Sample B gave a maximum residual fluoride concentration of 0.7126 mg/L (30.34%) at the 60th minute. Batch Adsorption Experiment 8 A 50 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm were mixed with 100 mL of 1 mg/L NaF solution and the pH of the mixtures was 7.78 and 9.47 respectively. A plot of residual fluoride concentration with time (Fig. 4.12) for the two limestone type is shown. Fig 4.12 Plot of Residual F- concentration against Time for 50 g mass (2000-6350 μm) samples in 1 mg/L NaF 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100R e si d u al F C o n c () m g/ L Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 82 Sample A recorded a maximum residual fluoride concentration of 0.5019 mg/L (54.26%) at the 60th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 0.6541 mg/L (36.06%) at the 45th minute (Fig. 4.12). Batch Adsorption Experiment 9 A plot of residual fluoride concentration with time (Fig. 4.13) for 100 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm mixed with 100 mL of 1 mg/L NaF solution is shown. The pH of the mixtures was 7.80 and 9.50 respectively. Fig 4.13 Plot of Residual F- concentration against Time for 100 g mass (2000-6350 μm) samples in 1 mg/L NaF Sample A recorded a reduction of fluoride at two instances. First fluoride reduction occurred at the 30th minute with concentration 0.5347 (51.27%) and another reduction at the 60th minute of concentration 0.6683 (39.10%). Sample B gave a maximum residual fluoride concentration of 0.7104 mg/L (30.56%) at the 60th minute (Fig. 4.13). 0 0.2 0.4 0.6 0.8 1 1.2 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 83 4.4.3 Effect of Varying Residence Time on Residual Fluoride Adsorption in 5 mg/L Fluoride Solution Batch Adsorption Experiment 10 A 10 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.15 and 9.20 respectively. A plot of residual fluoride concentration with time (Fig. 4.14) for the two limestone type is shown. Fig 4.14 Plot of Residual F- concentration against Time for 10 g mass (500-1000 μm) samples in 5 mg/L NaF Both sample A & B attained equilibrium at the 60th minutes (Fig. 4.14) with recorded maximum residual fluoride concentration of 1.3547 mg/L (73.18%) and 2.6513 (46.50%) respectively. Batch Adsorption Experiment 11 A plot of residual fluoride concentration with time (Fig. 4.15) for 50 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.32 and 9.47 respectively. 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 84 Fig 4.15 Plot of Residual F- concentration against Time for 50 g mass (500-1000 μm) samples in 5 mg/L NaF Both sample A & B attained equilibrium at the 60th minutes with recorded maximum residual fluoride concentration of 1.7436 mg/L (65.48%) and 2.1373 (56.88%) respectively (Fig. 4.15). Similar work by Yadev et al, 2012, showed a similar trend where the percentage removal of fluoride by four adsorbents at different contact times showed an increase percentage of fluoride removal. However, it gradually approached an almost constant value, denoting attainment of equilibrium at 60, 90, 105 and 75 min for the four adsorbents. Batch Adsorption Experiment 12 A 100 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.58 respectively. 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 85 Fig 4.16 Plot of Residual F- concentration against Time for 100 g mass (500-1000 μm) samples in 5 mg/L NaF A plot of residual fluoride concentration with time (Fig. 4.16), shows sample A recorded a maximum residual fluoride concentration of 2.0094 mg/L (60.21%) at the 75th minute of the 90-minute duration, while sample B gave a maximum residual fluoride concentration of 2.7571 mg/L (44.37%) at the 60th minute. Batch Adsorption Experiment 13 A 10 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.38 and 9.53 respectively. Fig 4.17 Plot of Residual F- concentration against Time for 10 g mass (1000-2000 μm) samples in 5 mg/L NaF 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 1 2 3 4 5 6 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 86 Both sample A & B attained equilibrium at the 60th minutes (Fig. 4.17) with recorded maximum residual fluoride concentration of 1.9748 mg/L (60.90%) and 2.8012 (43.48%) respectively. Batch Adsorption Experiment 14 A 50 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.56 respectively. Fig 4.18 Plot of Residual F- concentration against Time for 50 g mass (1000-2000 μm) samples in 5 mg/L NaF A plot of residual fluoride concentration with time (figure 4.18), for both sample A & B attained equilibrium at the 60th minute with recorded maximum residual fluoride concentration of 1.1773 mg/L (76.69%) and 2.1237 (57.15%) respectively. Batch Adsorption Experiment 15 A 100 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.60 respectively. 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 87 Fig 4.19 Plot of Residual F- concentration against Time for 100 g mass (1000-2000 μm) samples in 5 mg/L NaF Both sample A & B attained equilibrium at the 60th minute (Fig. 4.19) with recorded maximum residual fluoride concentration of 2.0613 mg/L (59.19%) and 3.5165 (29.05%) respectively. Batch Adsorption Experiment 16 A 10 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.39 and 9.60 respectively. Fig 4.20 Plot of Residual F- concentration against Time for 10 g mass (2000-6350 μm) samples in 5 mg/L NaF 0 1 2 3 4 5 6 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 1 2 3 4 5 6 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 88 A plot of residual fluoride concentration with time (Fig. 4.20), for sample A shows an appreciable increase in residual fluoride concentration until the 60th minute where the concentration gradually reduced to a concentration of 2.0534 at the 90th minute. Equilibrium was not established in this experiment. Sample B gave a maximum residual fluoride concentration of 1.4776 mg/L (70.19%) at the 60th minute. Batch Adsorption Experiment 17 A 50 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.37 and 9.54 respectively. Fig 4.21 Plot of Residual F- concentration against Time for 50 g mass (2000-6350 μm) samples in 5 mg/L NaF Both sample A & B attained equilibrium at the 60th minute (Fig. 4.21) with recorded maximum residual fluoride concentration of 3.2614 mg/L (35.43%) and 3.6808 (25.73%) respectively. 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 89 Batch Adsorption Experiment 18 A 100 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm were mixed with 100 mL of 5 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.60 respectively. Fig 4.22 Plot of Residual F- concentration against Time for 100 g mass (2000-6350 μm) samples in 5 mg/L NaF A plot of residual fluoride concentration with time (Fig. 4.22), shows sample A gave a marginal decrease in fluoride concentration of 3.5814 (29.09%) at the 60th minute. Sample B attained equilibrium at the 30th minute with recorded maximum residual fluoride concentration of 3.7315 mg/L (24.71%). 4.4.4 Effect of Varying Residence Time on Residual Fluoride Adsorption in 10 mg/L Fluoride Solution Batch Adsorption Experiment 19 A 10 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.32 and 9.44 respectively. 0 1 2 3 4 5 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 90 Fig 4.23 Plot of Residual F- concentration against Time for 10 g mass (500-1000 μm) samples in 10 mg/L NaF A plot of residual fluoride concentration with time (Fig. 4.23), shows sample A recorded a maximum residual fluoride concentration of 4.0029 mg/L (60.65%) at the 60th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 4.2127 mg/L (57.67%) at the 45th minute. The influence of contact time on the defluoridation capacity of powdered samples of Citrus limonum (lemon) leaf by Tomar et al., 2013, showed an increase in fluoride ion removal. Further increase in the contact time did not increase fluoride ion uptake due to sufficient deposition of fluoride ions on the available adsorption sites on the adsorbent materials. Batch Adsorption Experiment 20 A 50 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.36 and 9.51 respectively. 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 91 Fig 4.24 Plot of Residual F- concentration against Time for 50 g mass (500-1000 μm) samples in 10 mg/L NaF A plot of residual fluoride concentration with time (Fig. 4.24), shows sample A recorded a maximum residual fluoride concentration of 4.5077 mg/L (55.69%) at the 60th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 6.2341 mg/L (37.36%) at the 45th minute. Batch Adsorption Experiment 21 A 100 g mass each of the two limestone (A & B) sample of grain size 500-1000 µm were mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.38 and 9.54 respectively. Fig 4.25 Plot of Residual F- concentration against Time for 100 g mass (500-1000 μm) samples in 10 mg/L NaF 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 2 4 6 8 10 12 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 92 Both sample A & B attained equilibrium at the 60th minutes (Fig. 4.25) with recorded maximum residual fluoride concentration of 4.1481 mg/L (59.22%) and 4.4943 (54.84%) respectively. Batch Adsorption Experiment 22 A 10 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.27 and 9.47 respectively Fig 4.26 Plot of Residual F- concentration against Time for 10 g mass (1000-2000 μm) samples in 10 mg/L NaF A plot of residual fluoride concentration (Fig. 4.26), shows both sample A & B attained equilibrium at the 60th minutes with recorded maximum residual fluoride concentration of 5.1789 mg/L (49.09%) and 5.2282 (47.46%) respectively Batch Adsorption Experiment 23 A 50 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm were mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.36 and 9.52 respectively. 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 93 Fig 4.27 Plot of Residual F- concentration against Time for 50 g mass (1000-2000 μm) samples in 10 mg/L NaF Sample A attained equilibrium at the 60th minute (Fig. 4.27) with recorded maximum residual fluoride concentration of 4.0857 mg/L (59.84%) and sample B recorded a marginal residual fluoride concentration of 6.036 (39.35%) at the 30th minute of the entire 90 minute duration. Batch Adsorption Experiment 24 A 100 g mass each of the two limestone (A & B) sample of grain size 1000-2000 µm mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.58 respectively. Fig 4.28 Plot of Residual F- concentration against Time for 100 g mass (1000-2000 μm) samples in 10 mg/L NaF 0 2 4 6 8 10 12 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 94 A plot of residual fluoride concentration with time (Fig. 4.28), shows sample A recorded a maximum residual fluoride concentration of 4.8541 mg/L (52.28%) at the 60th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 4.4015 mg/L (55.77%) at the 45th minute. The variation of fluoride adsorbed with time is also investigated by Sujana et al., (1997). It was observed that the amount of fluoride adsorbed increases with time as well as concentration. The amount of fluoride adsorbed per gram of sludge increased to attain a constant value after 2 hours. Batch Adsorption Experiment 25 A 10 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.38 and 9.55 respectively. Fig 4.29 Plot of Residual F- concentration against Time for 10 g mass (2000-6350 μm) samples in 10 mg/L NaF A plot of residual fluoride concentration with time (Fig. 4.29), indicates sample A attained equilibrium at the 45th minute with recorded maximum residual fluoride concentration of 5.0143 mg/L (50.71%) and sample B recorded a marginal residual 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 95 fluoride concentration of 7.5978 (23.65%) at the 60th minute of the entire 90 minute duration. Batch Adsorption Experiment 26 A 50 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.38 and 9.58 respectively. Fig 4.30 Plot of Residual F- concentration against Time for 50 g mass (2000-6350 μm) samples in 10 mg/L NaF A residual fluoride concentration with time (Fig. 4.30), shows sample A recorded a maximum residual fluoride concentration of 5.0797 mg/L (50.06%) at the 45th minute of the 90 minute duration, while sample B gave a maximum residual fluoride concentration of 5.6292 mg/L (43.44%) at the 60th minute. Batch Adsorption Experiment 27 A 100 g mass each of the two limestone (A & B) sample of grain size 2000-6350 µm mixed with 100 mL of 10 mg/L NaF solution. The pH of the mixtures was 8.40 and 9.60 respectively. 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 University of Ghana http://ugspace.ug.edu.gh 96 Fig 4.31 Plot of Residual F- concentration against Time for 100 g mass (2000-6350 μm) samples in 10 mg/L NaF Both sample A & B attained equilibrium at the 45th minutes (Fig. 4.31) with recorded maximum residual fluoride concentration of 5.2904 mg/L (47.99%) and 5.3254 (46.49%) respectively. From the various results, maximum percentage adsorption of fluoride occurred at the 60th minutes for both limestone samples (A & B) and NaF concentrations (1, 5 and 10 mg/L). However, there were few that had their maximum percentage adsorption at the 45th minute. 4.4.5 Effect of Grain Size on Percentage Mean Fluoride Adsorption In this experiment, the grain sizes of the different samples are compared and their mean percentage fluoride adsorption compared. 4.4.5.1 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 1 mg/L NaF Solution Fig 4.32 Plot of % Mean Adsorption against Mass of sample EKL-R102 in 1 mg/L 0 2 4 6 8 10 0 20 40 60 80 100 R e si d u al F C o n c (m g/ L) Time (mins) D01 R102 0 10 20 30 40 50 60 70 10 50 100 % M e an A d so rp ti o n Mass (g) (500-100) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 97 Grain size of 1000-2000 µm recorded maximum mean fluoride adsorption of 57.27% for the 10 g of the sample whiles grain size (2000-6350 µm) recorded maximum mean % adsorption of 47.02% and 40.35% for the 50 and 100 g mass of the sample respectively (Fig. 4.32). Although large surface area (for grain size 500-1000 µm) should account for high adsorbing site for high fluoride removal, the above result was due to the crumpling of the sample as a result of the cementing nature (sticky with liquid medium) of the sample. This results in a lesser exposure of the surface area of the sample to the fluoride ions for adsorption. Wang et al., (2012), investigated the impact of the size of reactive materials on iron removal effectiveness. The result indicated that, iron removal efficiencies are strongly affected by particle size. Though larger sized particles removed enough of the 50 mg/L Fe (II) for the final concentration to fall below 0.3 mg/L, smaller sized particles had large surface area leading to higher surface capacity for higher adsorption and reaction (Stumm and Morgan, 1996). Also, one would expect the smaller particle size to give a greater percentage removal because of the surface area, but as the particle size increases, the number of micro pores on the adsorbent also increases. The increase in micro pores increases the number of accessible sites, hence increase in percentage adsorption, (Eneida et al., 2005) University of Ghana http://ugspace.ug.edu.gh 98 4.4.5.2 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 1 mg/L NaF Solution Fig 4.33 Plot of % Mean Adsorption against Mass of sample EKL-D01 in 1 mg/L Grain size of 1000-2000 µm recorded maximum mean fluoride adsorption of 31.55% for the 10 g of the sample whiles grain size (500-1000 µm) and (1000-2000 µm) recorded maximum mean % adsorption of 32.86% and 24.15% for the 50 and 100 g mass of the sample respectively (Fig. 4.33). Although large surface area (for grain size 500-1000 µm) should have accounted for high adsorbing site for high fluoride removal, the same reason given for sample EKL- R102 (500-1000 μm) in section 4.4.5.1 is the same for this sample as well as its result. Limestone sample EKL-R102 recorded high fluoride adsorption in the stated grain sizes than sample EKL-D01. This was due to the pH of the limestone-fluoride mixture and the composition of the sample type. More alkaline medium provides more hydroxide ions (OH-) into the medium where there is a competition between the fluoride ions (F-) and the hydroxide ions (OH-) for adsorption sites, (Karthikeyan and Elango, 2007). 0 5 10 15 20 25 30 35 10 50 100 % M e an A d so rp ti o n Mass (g) (500-1000) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 99 Also since sample EKL-D01 have some dolomite minerals in its composition [CaMg(CO3)2], the reactivity of the Mg2+ with F- is slow as compared to the reactivity of Ca2+ with F- in solution. This is due to their ionic sizes where Ca2+ has a bigger ionic size than Mg2+. 4.4.5.3 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 5 mg/L NaF Solution Fig 4.34 Plot of % Mean Adsorption against Mass of sample EKL-R102 in 5 mg/L A plot of percentage mean adsorption against mass (Fig. 4.34), shows grain size (500- 1000 µm) recorded maximum mean fluoride adsorption of 49.96% for the 10 g of the sample as against 45.37% and 25.64% for grain sizes 1000-2000 and 2000-6350 µm respectively. This result indicates that, the larger the surface area, the more the adsorption sites for fluoride adsorption. Surface area is closely associated with available adsorption sites and surface reactivity. The more the surface area, the more rapidly the adsorbate gets onto the adsorbent (Wang et al., 2012). The 50 g mass sample with grain size (1000-2000 µm) recorded maximum mean % adsorption of 62.96% whiles grain sizes 500-1000 and 2000-6350 µm gave mean % adsorption of 54.96% and 34.66% respectively. 0 10 20 30 40 50 60 70 10 50 100 % M e an A d so rp ti o n Mass (g) (500-1000) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 100 In terms of the 100 g mass, 1000-2000 µm grain size recorded the highest % fluoride adsorption of 50.44%. This is followed by grain size 500-1000 and 2000-6350 µm with % fluoride adsorption of 28.19% and 20.22% respectively. Grain size (2000-6350 μm) recorded the minimum percentage fluoride adsorption because, the bigger the grain size, the smaller the surface area for adsorption. The smaller grain size (500-1000 μm) should have recorded the highest percentage adsorption. This is because, it gives a large surface area as compared to the other grain sizes. But the result does not correlate with the stated assumption. The reason might be due to the stated reason given in Section 4.4.5.1. 4.4.5.4 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 5 mg/L NaF Solution Fig 4.35 Plot of % Mean Adsorption against Mass of sample EKL-D01 in 5 mg/L Grain size of 500-1000 µm for both 50 and 100 g mass recorded maximum mean fluoride adsorption of 40.95% and 30.02% respectively (Fig. 4.35). This result shows that, the smaller the grain size, the larger the surface area available for adsorption. An investigation into the use of laterite for the removal of fluoride from contaminated 0 5 10 15 20 25 30 35 40 45 10 50 100 % M e an A d so rt io n Mass (g) (500-1000) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 101 drinking water indicates that, finer particles have a large surface area resulting in a higher adsorption rate (Sarkar et al., 2006). Although, grain size (2000-6350 µm) recorded a mean % adsorption of 37.54% for 10 g mass category, this might be attributed to the crumpling of the smaller grain particles together as a result of the cementing nature of the limestone sample. 4.4.5.5 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-R102) in 10 mg/L NaF Solution Fig 4.36 Plot of % Mean Adsorption against Mass of sample EKL-R102 in 10 mg/L A plot of percentage mean adsorption against mass for sample EKL-R102 (Fig. 4.36), shows grain size (500-1000 µm) for both 10 and 100 g mass recording maximum mean fluoride adsorption of 47.45% and 49.63% respectively. This result shows that, the smaller the grain size, the larger the surface area and hence the more the exposure of active sites of the adsorbent for fluoride adsorption (Wang et al., 2012). The 50 g mass category shows grain size (1000-2000 µm) to have recorded the highest mean % adsorption of 50.96%. 0 10 20 30 40 50 60 10 50 100 % M e an A d so rp ti o n Mass (g) (500-1000) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 102 4.4.5.6 Effect of Grain Size on Percentage Mean Fluoride Adsorption for Sample (EKL-D01) in 10 mg/L NaF Solution Fig 4.37 Plot of % Mean Adsorption against Mass of sample EKL-D01 in 10 mg/L Grain size (500-1000 µm) recorded maximum mean fluoride adsorption of 41.80% for the 10 g of the sample as against 41.25% and 17.73% for grain sizes 1000-2000 and 2000-6350 µm respectively (Fig. 4.37). This result shows that, the larger the surface area, the more the adsorption sites for fluoride adsorption. For 50 g mass category, grain size (2000-6350 µm) recorded the highest mean % adsorption of 36.67% whiles grain sizes 1000-2000 and 500-1000 µm gave mean % adsorption of 35.51% and 31.50% respectively. This is as a result of the inability of the magnetic rod to stir the fine grained samples in the mixture uniformly. However much surface area is not exposed for grain sizes 500-1000 µm for more adsorption sites to translate into high fluoride adsorption. In terms of the 100 g mass category, grain size (1000-2000 µm) recorded the highest % fluoride adsorption of 50.68%. This is followed by grain size 500-1000 and 2000- 0 10 20 30 40 50 60 10 50 100 % M e an A d so rp ti o n Mass (g) (500-1000) (1000-2000) (2000-6350) University of Ghana http://ugspace.ug.edu.gh 103 6350 µm with % fluoride adsorption of 48.57% and 41.52% respectively. This can also be attributed to the reason stated for the 50 g mass category. 4.4.6 Effect of Fluoride Concentration Variation on Percentage Mean Fluoride Adsorption The Tables (Table 4.4, 4.5 and 4.6) give the % fluoride adsorption for the different concentrations (1, 5 and 10 mg/L). Table 4.4: Percentage fluoride adsorption for 1 mg/L fluoride solution EKL-R102 EKL-D01 Concentration: 1 mgF-/L Mass (g) Particle Size (μm) Mean % adsorption Mean Adsorption capacity (mg/g) Mas s (g) Particle Size (μm) Mean % adsorption Mean Adsorption capacity (mg/g) 10 10 10 500-1000 1000-2000 2000-6350 50.893 57.272 32.942 5.58 6.28 3.61 10 10 10 500-1000 1000-2000 2000-6350 28.39 31.55 16.14 2.90 3.23 1.65 50 50 50 500-1000 1000-2000 2000-6350 42.639 44.657 47.022 4.68 4.90 5.16 50 50 50 500-1000 1000-2000 2000-6350 32.86 27.28 24.56 3.36 2.79 2.51 100 100 100 500-1000 1000-2000 2000-6350 28.187 29.538 40.347 3.09 3.24 4.43 100 100 100 500-1000 1000-2000 2000-6350 20.76 24.15 23.60 2.12 2.47 2.41 The mean % fluoride adsorption for sample EKL-R102 and EKL-D01 in 1 mg/L solution (Table 4.4) is 41.50% and 25.48% respectively. University of Ghana http://ugspace.ug.edu.gh 104 Table 4.5: Percentage fluoride adsorption for 5 mg/L fluoride solution EKL-R102 EKL-D01 Concentration: 5 mgF-/L Mas s (g) Particle Size (μm Mean % adsorption Mean Adsorption capacity (mg/g) Mas s (g) Particle Size (μm) Mean % adsorption Mean Adsorption capacity (mg/g) 10 10 10 500-1000 1000-2000 2000-6350 49.962 45.369 25.640 25.23 22.91 12.95 10 10 10 500-1000 1000-2000 2000-6350 29.17 32.54 37.54 14.46 16.12 18.60 50 50 50 500-1000 1000-2000 2000-6350 54.962 62.958 34.663 27.75 31.79 17.50 50 50 50 500-1000 1000-2000 2000-6350 40.95 36.69 14.58 20.29 18.18 7.22 100 100 100 500-1000 1000-2000 2000-6350 28.186 50.442 20.219 14.23 25.47 10.21 100 100 100 500-1000 1000-2000 2000-6350 30.02 15.93 18.95 14.87 7.89 9.39 The mean % fluoride adsorption for sample EKL-R102 and EKL-D01 in 5 mg/L solution (Table 4.5) is 41.38% and 28.48% respectively. Table 4.6: Percentage fluoride adsorption for 10 mg/L fluoride solution EKL-R102 EKL-D01 Concentration: 10 mgF-/L Mas s (g) Particle Size (μm Mean % adsorption Mean Adsorption capacity (mg/g) Mas s (g) Particle Size (μm) Mean % adsorption Mean Adsorption capacity (mg/g) 10 10 10 500-1000 1000-2000 2000-6350 47.448 40.764 39.793 25.23 22.91 12.95 10 10 10 500-1000 1000-2000 2000-6350 41.80 41.25 17.73 14.46 16.12 18.60 50 50 50 500-1000 1000-2000 2000-6350 46.123 50.962 36.429 27.75 31.79 17.50 50 50 50 500-1000 1000-2000 2000-6350 31.50 35.51 36.67 20.29 18.18 7.22 100 100 100 500-1000 1000-2000 2000-6350 49.627 45.229 43.981 14.23 25.47 10.21 100 100 100 500-1000 1000-2000 2000-6350 48.57 50.68 41.52 14.87 7.89 9.39 University of Ghana http://ugspace.ug.edu.gh 105 The mean % fluoride adsorption for sample EKL-R102 and EKL-D01 in 10 mg/L solution (Table 4.6) is 44.48% and 38.36% respectively. Fig 4.38 Plot of percentage fluoride adsorption for varying fluoride concentrations Percentage adsorption appreciated marginally for sample EKL-R102 (41.50% - 44.48%) and sample EKL-D01 (25.48% - 38.36%) (Fig. 4.38) for concentrations 1, 5 and 10 mg/L respectively. It can be deduced that, the higher the concentration of the adsorbate, the higher the % fluoride adsorption (Kebede et al., 2014). This study confirmed the observation made by Malakootian et al. (2011) that initial fluoride concentration influences the amount of adsorbate adsorbed per unit mass of the adsorbent, q (mg/g). 4.4.7 Effect of pH of Fluoride - Limestone Mixture on Percentage Mean Fluoride Adsorption The Table (4.7) gives the variation of pH of the different limestone samples and their corresponding % mean fluoride adsorption. 0 5 10 15 20 25 30 35 40 45 50 1 5 10 % M e an F - A d so rp ti o n Conc (mg/L) % F- Adsorp (R102) % F- Adsorp (D01) University of Ghana http://ugspace.ug.edu.gh 106 Table 4.7: pH variation of F- - Limestone mixture with % mean fluoride adsorption Type of Limestone Conc.of F- Solution pH of F- - Limestone Mixture % Mean Fluoride Adsorption EKL-R102 1 7.65 - 7.80 41.50 EKL-R102 5 8.15 - 8.40 41.38 EKL-R102 10 8.27 - 8.40 44.48 EKL-D01 1 9.38 - 9.50 25.48 EKL-D01 5 9.20 - 9.60 28.48 EKL-D01 10 9.44 - 9.60 27.93 Sample EKL- R102 gave a higher % mean fluoride adsorption of 42.45% for pH range (7.65 – 8.40) compared to 27.30 in EKL-D01of pH range (9.38 – 9.60) (Table 4.7). This was due to the competition between the hydroxide (OH-) and fluoride ions (F-) for adsorption sites (Karthikeyan and Elango, 2007) 4.4.8 Effect of Varying Adsorbent Dose on Percentage Mean Fluoride Adsorption The evaluation of the adsorbent dose on adsorption efficiency was carried out by varying the adsorbent mass (10, 50 and 100 g) for the same volume (100 mL) of fluoride solution for the two limestone samples. The results were found to be as follows. University of Ghana http://ugspace.ug.edu.gh 107 Table 4.8: Variation of Adsorbent Dose on % Fluoride Adsorption for Sample EKL-R102 Mass (g) % F- Adsorption (500 – 1000 µm) % F- Adsorption (1000 – 2000 µm) % F- Adsorption (2000 – 6350 µm) Conc. of soln. (mg/L) 10 50 100 50.89 42.64 28.19 57.27 44.66 29.54 32.94 47.02 40.35 1 10 50 100 49.96 54.96 28.19 45.37 62.96 50.44 25.64 34.66 20.22 5 10 50 100 47.45 46.12 49.63 40.76 50.96 45.23 39.79 36.43 43.98 10 Grain size 2000-6350 μm (1 mg/L), grain size 1000-2000 μm ( 5 mg/L) and all three grain sizes in the 10 mg/L solution gave an appreciable increase in % fluoride adsorption with respect to increasing adsorbent dose. On the other hand, grain sizes 500-1000 μm (1 and 5 mg/L), grain size 1000-2000 μm (1 mg/L) and grain size 2000- 6350 μm (5 mg/L) showing a decrease trend in % fluoride adsorption (Table 4.8). Table 4.9: Variation of Adsorbent Dose on % Fluoride Adsorption for Sample EKL-D01 Mass (g) % F- Adsorption (500 – 1000 µm) % F- Adsorption (1000 – 2000 µm) % F- Adsorption (2000 – 6350 µm) Conc. of soln. (mg/L) 10 50 100 28.38 32.86 20.76 31.55 27.28 24.15 16.14 24.56 23.60 1 10 50 100 29.17 40.95 30.02 32.54 36.69 15.93 37.54 14.58 18.95 5 10 50 100 41.80 31.50 48.57 41.25 35.51 50.68 17.73 36.67 41.52 10 University of Ghana http://ugspace.ug.edu.gh 108 All the three grain sizes of sample EKL-D01 in concentration 10 mg/L gave an appreciable increase in % fluoride adsorption with respect to increasing adsorbent dose. Grain sizes 500-1000 μm (1 mg/L), grain size 1000-2000 μm (1 and 5 mg/L) and grain size 2000-6350 μm (5 mg/L) recorded a decrease in % fluoride adsorption with respect to increasing adsorbent dose (Table 4.9) Fig 4.39 Plot of % F- Adsorption against varying mass of samples When a comparative analysis of the different masses was done when the concentration of the solution was kept constant, a mean percentage adsorption for sample EKL- R102 for masses 10, 50 and 100 g gave 43.33%, 46.71% and 37.31% respectively. On the other hand, sample EKL-D01 recorded 30.68%, 31.18% and 30.46% for the mean percentage adsorption for masses 10, 50 and 100 respectively. Although different masses in different concentrations gave different % adsorptions (Table 4.8 and 4.9), the mean % adsorption shows 50 g mass (EKL-R102) recording the highest mean % fluoride adsorption. This trend suggests that after a certain dose of the adsorbent, the maximum adsorption is attained and the amount of ions bound to the adsorbent and the amount of free ions remains constant (equilibrium) even with 0 10 20 30 40 50 10 50 100 % F - A d so rp ti o n Mass (g) (R102) (D01) University of Ghana http://ugspace.ug.edu.gh 109 further addition of the dose of the adsorbent. This is similar to studies reported by Abdel-Ghani et al., (2007); Alok Mittal, (2006); and Murat Teker et al., (1999). The 100 g mass recorded the lowest mean % adsorption in the two samples. This may be attributed to the inability of more adsorbing sites to be exposed as the magnetic rod could not evenly stir the mixture uniformly. Also, the volume of the beaker in which the mixture (100 g) was contained could also have an influence on the exposure of more adsorbing sites of the adsorbents ((Dorris et al., 2003)). 4.5 Column Adsorption Experiment The results of the physico-chemical and anion analysis conducted on the ten (10) real water samples from the Bongo district is presented in Table 4.10 University of Ghana http://ugspace.ug.edu.gh 109 Table 4.10 Physico-chemical and Anion Analysis of water samples from Bongo district Sample ID A B C D E F G H I J WHO (2003) pH 8.25 7.74 7.95 8.34 8.24 8.17 8.08 8.30 8.22 8.06 6.5-8.5 EC 286 287 453 422 388 319 211 329 394 434 1400 Sal 0.1 0.1 0.2 0.2 0.2 0.1 0.1 0.1 0.2 0.2 - TDS 127.0 126.0 200.0 186.0 170.9 140.2 92.0 144.4 173.0 189.6 1000 Turb 4 0 0 0 0 0 0 1 0 0 5 Col 0 0 0 0 0 0 0 0 0 0 15 F- 17.187 10.657 5.406 3.816 3.562 6.152 6.192 7.478 3.379 3.350 1.5 Cl- 11.430 14.017 39.573 20.273 27.452 8.872 2.166 18.934 24.114 23.407 250 NO3- 64.611 52.005 198.035 122.193 80.072 36.802 13.917 80.456 96.508 72.742 50 SO42- 8.249 10.689 42.358 46.471 48.188 51.988 - 10.286 22.916 21.875 250 PO43- <0.001 0.024 <0.001 0.015 <0.001 0.014 <0.001 <0.001 <0.001 0.0084 3 [A = BAB1, B = BAB2, C = BNB3, D = BNB4, E = BNB5, F = BNB6, G = BNB7, H = BNN8, I = BZB9, J = BAB10] University of Ghana http://ugspace.ug.edu.gh 110 4.5.1 Anion Analysis from Column Adsorption Experiment Based on the usage of the boreholes in the communities, Samples BNB6 and BNN8 were selected for the Column Adsorption experiment. Although, Samples BAB1 and BAB2 recorded the highest fluoride concentration, they are not used for this study because, they are not been used by the communities and are referred to as capped boreholes. The water samples were run over three mini-column beds of height 20, 30 and 40 cm loaded with limestone samples EKL-R102. Aliquots were taken from each set-up at every 15-minutes interval for the 90-minutes duration. Fluoride and other anions were determined with the ICS-90 Ion Chromatographic System (APPENDIX H3). A plot of residual fluoride concentration with time is shown (Fig. 4.40 and 4.41). Fig 4.40 Plot of Residual F- Concentration against Time for water sample BNB6 Fig 4.41 Plot of Residual F- Concentration against Time for water sample BNN8 0 0.5 1 1.5 2 2.5 3 3.5 0 20 40 60 80 100 R e si d u al F - C o n c (m g/ L) Time (mins) 20cm tube 30cm tube 40cm tube 0 0.5 1 1.5 2 2.5 3 0 20 40 60 80 100R e si d u al F - C o n c () m g/ L Time (mins) 20cm tube 30cm tube 40cm tube University of Ghana http://ugspace.ug.edu.gh 111 The adsorbent in mini-column bed (433.939 g) with height 40 cm gave a maximum mean percentage adsorption of approximately 86% as compared to 78% and 74% for bed heights 30 and 20 cm respectively. The high adsorption was due to the presence of more adsorption sites present for the fluoride ions (adsorbate) to get attached. The three set-ups were able to reduce the fluoride content below WHO recommended level of 1.5 mg/L. The reduction occurred at different times in each set-up. The 20 cm mini-column bed attained equilibrium with a maximum residual fluoride reduction of 1.13 at the 45th minute (Fig 4.41) after which the concentration begins to appreciate due to saturation of the adsorption sites. The mean percentage adsorption gave approximately 75%. In the 30 cm mini-column bed, equilibrium is attained at the 90th minutes that gave residual fluoride concentration of 1.13 mg/L. Though the reaction did not give a clear uniform path, it rises and falls at different times but the maximum reduction occurred at the 90th minutes. One of the three set-ups (20 cm height mini-column bed) was able to reduce fluoride concentration in the water sample (BNB6) from 6.1519 mg/L to 0.13 mg/L within the first fifteen minutes (Fig. 4.39). The 30 and 40 cm column heights recorded 1.84 and 1.59 mg/L residual fluoride concentrations also at the 15th minute of the 90 minutes duration. Comparing the efficiency of the adsorbent in each set-up for the two water sample defluoridation processes, average percentage fluoride adsorption that occurred in water sample BNN8 was approximately 80% as compared to 67% in BNB6. Despite University of Ghana http://ugspace.ug.edu.gh 112 the same adsorbent been used in the two processes, the variation might be due to the concentrations of the co-existing anions present in the water samples. Table 4.11 Summary of the effect of co-existing anions in the water samples before and after the defluoridation process. Parameters BNB6 BNN8 Initial Final % Adsorbed Initial Final % Adsorbed F- 6.152 2.058 66.55 7.478 1.526 79.60 Cl- 8.872 7.519 15.25 18.934 16.166 14.62 SO42- 51.988 15.152 70.85 10.286 8.247 19.83 NO3- 36.802 27.959 24.03 80.456 33.10 58.85 PO43- 0.014 < 0.001 - < 0.001 < 0.001 - Initial concentrations of Cl- and NO3- in BNN8 are higher than in sample BNB6 (Table 4.12), whiles initial concentrations of SO42- and PO43- are much higher in sample BNB6 than BNN8. The effect of these anions on fluoride adsorption are in the order PO43- > SO42- > Cl- (Nabizadeh et al., 2015) The percentage of sulphate ion adsorbed (19.83%) onto the adsorbent in water sample BNN8 was lower compared to the percentage of sulphate ion adsorbed (70.85%) in sample BNB6. The greater the sulphate ion adsorbed onto the adsorbent, the lower the removal of fluoride from the water sample (Nabizadeh et al., 2015). The findings of the current study are consistent with those of Shao-Xiang et al., (2009) who examined the effects of coexisting ions on fluoride removal by manganese oxide-coated alumina. From his study, NO3- and Cl- showed negligible University of Ghana http://ugspace.ug.edu.gh 113 effect on the removal of fluoride. However, other common coexisting ions affected fluoride removal in the order of PO43- > SO42-. Some anions could enhance columbic repulsion forces and compete with fluoride for the active sites, readily decreasing the adsorption (Wambu et al., 2012). Generally, multivalent anions are absorbed more readily than monovalent anions. The impact of major anions on fluoride adsorption followed the order of CO32– > PO43– > SO42– > Cl– (Onyango et al., 2004). The results of this study indicate that sulphate is the greatest competitor for fluoride followed by nitrate and chloride. Similar phenomenon has been observed in the case of fluoride removal by nano-magnesia (Onyango et al., 2004). The adsorption mechanism of the anions onto adsorbents is significantly dependent on the physico- chemical properties of anions and their interaction with the adsorbent surface. Properties of anions such as the solubility, ionic radius, hydration energy and bulk diffusion coefficient are crucial for the selective adsorption of anions (Onyango et al., 2004). Johnston and Heijnen, (2002), in their study corroborated that, competition of ions adsorbing onto the active sites of the adsorbents are associated with the size of the ion, surface charges on the adsorbent which become more negative at high pH, and differential pore development on the heterogeneous adsorbent. University of Ghana http://ugspace.ug.edu.gh 114 CHAPTER FIVE CONCLUSION AND RECOMMENDATIONS 5.1 CONCLUSION 5.1.1 Mineralogy Phase identification of the crystal nature of the limestone samples achieved using XRD revealed that the limestone samples from Oterkpolu were dominated by Calcite minerals, with some a few amount of Dolomite minerals [Calcite – 95%, Silicon oxide –5% for sample EKL-R102 and Calcite – 68%, Dolomite – 22%, Silicon oxide – 10% for sample EKL-D01]. Petrographic Thin Section was used to identify the percentage (%) mineral composition of the limestone samples. Based on the results obtained, the limestone samples with the following compositions were selected for the study: EKL-R102 gave Calcite – 96%, Quartz – 4% whiles EKL-D01 also gave Calcite – 85%, Quartz – 15%. The Petrographic Thin Section also revealed that some of the samples may have undergone a little deformation or metamorphism, evidenced by fractures, veins and crystalline quartz in the micrograph of the Petrographic Thin Section slides. During sample collection at the Oterkpolu limestone deposit site, the reaction between hydrochloric acid (a mineral acid) and the limestone sample was used to aid identification of the calcium carbonate (calcite). Limestone samples that gave a fizzing reaction on reaction with mineral acid [10% v/v HCl] were selected for the study because that indicates the limestone sample is made up of calcium carbonate (calcite). University of Ghana http://ugspace.ug.edu.gh 115 5.1.2 Radiological Safety Assessment of naturally occurring radionuclides was carried out on the limestone samples to be used for the defluoridation process to evaluate the hazards these may have on the defluoridated water to be used by the public. The Activity Concentration of the samples were measured using High Purity Germanium (HPGe) based gamma- ray spectrometer. The mean activity concentrations for 238U, 232Th and 40K were found to be 2.0 ±1.5, 1.7 ±1 and 21.9 ±13.4 Bq/kg respectively for eight (8) limestone samples from Oterkpolu. The Annual Effective Dose (AED) represents the stochastic health risk to the whole body when the sum of each organ or tissue is being irradiated. This was also found to be 0.13 mSv/yr. The recommended value by UNSCEAR, (2000) is 0.40 mSv/yr. Since the estimated Annual Effective Dose calculated is lower than the recommended value, there seems to be no potential radiological health hazard associated with Oterkpolu limestone to be used in the water defluoridation process. 5.1.3 Particle Size - % Adsorption Limestone samples were divided into three groups of grain sizes. These are 500-1000, 1000-2000 and 2000-6350 μm. This was done to determine the rate of adsorption of fluoride onto the different adsorbent surfaces since the nature of sample (particle size) determines the surface area available for the fluoride ions to adhere to. The mean percentage fluoride adsorption (for the first 60th minute) for sample EKL- R102 for concentration of 1, 5 and 10 mg/L for grain sizes 500-1000 μm, 1000-2000 μm and 2000-6350 μm were 44.22%, 47.63% and 35.67% respectively. Sample EKL- D01 for the same concentrations and grain sizes were 33.77%, 32.84% and 25.70% University of Ghana http://ugspace.ug.edu.gh 116 respectively. From the results, the optimum grain size that gave an optimum percentage fluoride adsorption was 1000-2000 μm. 5.1.4 Resident Time - % Absorption The resident time for the adsorption process was to determine the time equilibrium was established. The equilibrium time determines when maximum fluoride was removed from the solution by the adsorbent. After this time, fluoride ions are again released into the medium to increase the concentration. The optimum resident time suitable for maximum fluoride removal was within the first 60th minute although a few samples gave a resident time of 45 minutes, 5.1.5 Adsorbent Dose - % Adsorption The mass of the adsorbent dose determines the adsorption rate as this factor determines the number of active sites present for adsorption. From the study, the mean percentage adsorption for sample EKL-R102 for mass 10, 50 and 100 g (keeping concentration of solution constant) were 43.33%, 46.71% and 37.31% respectively. On the other hand, when grain size was kept constant, the mean percentage adsorption for the same sample gave 43.34% 46.71 and 37.31 respectively. For sample EKL-D01, when concentration was kept constant, the mean percentage adsorption for mass 10, 50 and 100 g was 30.68%, 31.18% and 30.46% respectively. When grain size was kept constant, the mean percentage fluoride adsorption gave 30.67%, 31.33 and 30.41% for 10, 50 and 100 g adsorbent dose. University of Ghana http://ugspace.ug.edu.gh 117 From the results obtained, the 50 gram mass recorded the highest mean percentage adsorption. 5.1.6 Fluoride Concentration - % Adsorption Fluoride concentrations were varied (1, 5 and 10 mg/L) in this study to cater for circumstances where the fluoride concentrations in affected communities are below the minimum WHO level of 1.5 mg/L and extreme situations where the concentration is up to 10 mg/L. From the study, increasing the concentration of the solution from 1-10 mg/L recorded a marginal increase in the mean percentage adsorption for the two adsorbents. Thus, sample EKL-R102 increased from 41.50% to 44.48% whiles sample EKL-D01 increased from 25.48% - 38.36%. 5.1.7 pH - % Adsorption of Mixture (Limestone - Fluoride solution) The pH of a medium is important in predicting the efficiency of adsorption since there is a competetion among hydrogen ions (H+), hydroxide ions (OH-) and fluoride ions (F-) onto the adsorbent surface. The pH range for sample EKL-R102 and EKL-D01 were found to be 7.65-8.40 and 9.20-9.60 respectively. Sample EKL-R102 recorded a mean percentage adsorption of 42.45 as against 27.30 for sample EKL-D01. From the results, it can be deduced that, media with low pH value enhances more adsorption sites for fluoride ions to adsorb onto the adsorption sites of the adsorbent since the positively charged adsorbent attracts fluoride ions electrostatically than in high pH media where OH- compete with the fluoride ions leading to a lower defluoridation. University of Ghana http://ugspace.ug.edu.gh 118 5.1.8 Column Adsorption The developed defluoridation technique was used on real water samples from affected communities in northern Ghana to test the efficiency and efficacy of the adsorbent in a natural situation. Water samples were taken from the Bongo district of the upper east region of Ghana. The district was chosen based on the high reported incidence of fluorosis as a result of high fluoride concentrations in their ground waters. Groundwater from ten (10) communities in the Bongo district was collected. Two samples (BNB6 and BNN8) recorded 6.2 and 7.5 mg/L fluoride concentrations. The pHs of the samples before the defluoridation process were 8.17 and 8.30 respectively. After the defluoridation process, fluoride concentrations in the two water samples were reduced to 2.0 and 1.5 mg/L respectively constituting 67% and 80% mean percentage fluoride reduction. Three mini-column glass beds of heights 20, 30 and 40 cm were loaded with limestone sample EKL-R102 of masses (251.20, 376.80, 502.40 g) respectively. Running the water samples on the column beds, aliquots of the filtrate solution were taken at 15 minutes intervals for duration of 90 minutes. Maximum fluoride reduction occurred between the first 45 minutes. Column bed with height 40 cm recorded maximum percentage fluoride reduction of 86% for water sample BNN8 whiles column bed of height 20 cm recorded a percentage fluoride adsorption of 73% for water sample BNB6. University of Ghana http://ugspace.ug.edu.gh 119 5.2 RECOMMENDATIONS 1. As a result of the unavailability of facilities and the limited time for the study, chemical analysis on the adsorbent was not carried out. I recommend subsequent studies should incorporate the chemical analysis of the adsorbent to make better inference. 2. Other studies can also assess the effectiveness of the other limestone sites in Ghana. 3. To enhance the % fluoride adsorption of the limestone, further studies should be conducted on acidification of the limestone sample using Citric Acid from lemon leaves 4. To determine the radiological safety of the treated water after the defluoridation process, the water should be analyzed for NORMs again. University of Ghana http://ugspace.ug.edu.gh 120 REFERENCES Abdelgawad, A.M.; Watanabe, K.; Takeuchi, S.; Mizuno, T. (2009). The origin of fluoride-rich groundwater in Mizunami area, Japan—Mineralogy and geochemistry implications. Eng. Geol. 108, 76–85. Abdel-Ghani, N.T.M. Hefray, G.A.F. EL-Chaghaby (2007). Removal of Lead from aqueous solution using low cost abundantly available adsorbent. Int. J. Environ. Sci. Tech. 4(1): 67-73 Abe, I., Iwasaki,S., Tokimoto, T., Kawasaki, N., Nakamura, T. and Tanada, S. (2004) Adsorption of fluoride ions onto carbonaceous materials, J. Colloid Interface Sci. 275: 35–39. Abugri D. A and Pelig-Ba K.B. 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University of Ghana http://ugspace.ug.edu.gh 137 APPENDIX A A1: Peak and Pattern list of limestone sample EKL-Bk03 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 20.8791 169.09 0.1181 4.25467 0.98 22.0481 212.87 0.1181 4.03165 1.24 24.0846 367.95 0.1181 3.69517 2.14 26.6647 760.50 0.1574 3.34319 4.42 27.9150 125.58 0.1574 3.19622 0.73 30.9732 17219.33 0.1968 2.88727 100.00 33.5616 576.87 0.1574 2.67027 3.35 35.3333 389.39 0.1574 2.54034 2.26 37.3822 618.53 0.1574 2.40568 3.59 39.4719 38.35 0.2362 2.28300 0.22 41.1496 1756.82 0.1968 2.19372 10.20 43.8165 233.99 0.1968 2.06618 1.36 44.9435 974.10 0.1968 2.01696 5.66 49.2514 205.02 0.2362 1.85015 1.19 50.5342 1205.30 0.1968 1.80616 7.00 51.0818 1356.29 0.2362 1.78807 7.88 58.8866 174.74 0.1968 1.56834 1.01 59.7946 337.24 0.2755 1.54668 1.96 62.0031 25.07 0.6298 1.49679 0.15 63.4247 261.67 0.2362 1.46662 1.52 64.5227 207.76 0.1181 1.44429 1.21 65.1639 126.42 0.2755 1.43162 0.73 66.0605 69.28 0.3936 1.41435 0.40 67.4013 353.14 0.1574 1.38944 2.05 70.4832 218.75 0.1574 1.33605 1.27 72.8887 83.84 0.3149 1.29778 0.49 74.7920 71.52 0.3149 1.26941 0.42 76.9734 120.97 0.4723 1.23879 0.70 79.7351 43.96 0.3936 1.20268 0.26 82.5994 83.86 0.3149 1.16809 0.49 86.6694 70.39 0.3149 1.12339 0.41 87.8762 183.30 0.1968 1.11105 1.06 Pattern List Visible Ref.Code Score Cpd Name Displ.[°2Th] Scale Fac. Chem. Formula 98-017-1518 62 Dolomite 0.000 0.954 C2 Ca1 Mg1 O6 03-065-0466 36 Silicon Oxide 0.000 0.036 O2 Si A2: Peak and Pattern list of limestone sample EKA-B01 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 8.7057 144.80 0.6298 10.15753 2.31 12.4842 136.01 0.2362 7.09042 2.17 19.7516 66.83 0.2362 4.49491 1.07 20.8773 298.35 0.1181 4.25502 4.77 21.9990 71.21 0.2362 4.04054 1.14 23.0946 296.88 0.1574 3.85128 4.74 23.9914 109.63 0.2362 3.70931 1.75 25.2437 45.52 0.4723 3.52806 0.73 26.6617 1668.30 0.1574 3.34356 26.66 27.9472 204.11 0.1181 3.19262 3.26 29.4505 4563.86 0.1574 3.03299 72.92 30.7670 6258.35 0.1574 2.90615 100.00 33.2454 81.46 0.3149 2.69494 1.30 35.0489 87.47 0.4723 2.56030 1.40 36.0222 397.14 0.1574 2.49332 6.35 36.5532 118.91 0.1181 2.45831 1.90 University of Ghana http://ugspace.ug.edu.gh 138 37.2778 155.96 0.1968 2.41217 2.49 39.4819 592.57 0.1968 2.28245 9.47 40.9538 362.72 0.1968 2.20375 5.80 42.4651 92.74 0.1968 2.12875 1.48 43.2271 476.83 0.1968 2.09298 7.62 44.7120 171.45 0.2362 2.02686 2.74 47.5743 421.63 0.1968 1.91138 6.74 48.5611 463.83 0.1968 1.87482 7.41 50.1314 316.61 0.1968 1.81972 5.06 50.9448 177.08 0.4723 1.79256 2.83 56.6696 64.02 0.2362 1.62431 1.02 57.4257 166.32 0.2755 1.60471 2.66 59.9987 118.70 0.3149 1.54191 1.90 60.7325 129.97 0.1181 1.52502 2.08 61.5364 86.86 0.2362 1.50701 1.39 63.1687 90.07 0.3936 1.47195 1.44 64.7757 129.45 0.3149 1.43926 2.07 65.6984 73.38 0.3936 1.42127 1.17 67.1529 78.04 0.3149 1.39398 1.25 70.3954 49.92 0.4723 1.33750 0.80 72.9962 55.42 0.2362 1.29614 0.89 81.6524 37.06 0.6298 1.17922 0.59 83.8549 73.07 0.3936 1.15377 1.17 Pattern List Visible Ref. Score Cpd Displ. Scale Chem. Formula Code Name [°2Th] Fac. 01-086-2334 65 Calcium Carbonate 0.000 0.431 Ca( C O3 ) 01-085-0795 48 Silicon Oxide 0.000 0.272 SiO2 98-017-1525 52 Dolomite 0.000 0.601 C2 Ca1 Mg1 O6 01-070-9131 13 Calcium Magnesium ..0.000 0.261 Ca0.23 Mg1.77( Si.. 01-073-2361 23 Calcium Magnesium ..0.000 0.533 Ca Mg ( C O3 )2 A3: Peak and Pattern list of limestone sample EKA-R01 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 8.8459 460.77 0.1574 9.99681 14.92 17.7474 122.91 0.1574 4.99774 3.98 19.7060 197.07 0.1968 4.50522 6.38 20.8591 393.26 0.1574 4.25869 12.74 22.0356 88.59 0.2362 4.03391 2.87 23.0862 245.36 0.1181 3.85266 7.95 24.0898 103.50 0.3936 3.69439 3.35 26.6456 2310.09 0.1181 3.34555 74.81 27.8820 148.40 0.2362 3.19993 4.81 29.4370 3087.94 0.1574 3.03435 100.00 30.7413 2357.41 0.1968 2.90851 76.34 30.9692 1635.19 0.1181 2.88763 52.95 33.1629 227.90 0.1968 2.70146 7.38 34.9357 213.16 0.2362 2.56833 6.90 36.0130 293.56 0.1574 2.49393 9.51 36.5553 179.72 0.1181 2.45817 5.82 37.2608 109.40 0.3936 2.41324 3.54 39.4583 431.87 0.1574 2.28376 13.99 41.0197 245.12 0.3149 2.20036 7.94 42.4331 104.59 0.2362 2.13029 3.39 43.1930 369.14 0.1574 2.09455 11.95 44.8147 140.37 0.3149 2.02245 4.55 47.5487 333.33 0.2362 1.91235 10.79 48.5327 327.47 0.2362 1.87585 10.60 50.1122 333.58 0.1574 1.82037 10.80 50.9666 152.58 0.4723 1.79184 4.94 56.5817 62.11 0.2362 1.62663 2.01 57.4269 157.95 0.1968 1.60468 5.12 59.9537 174.34 0.1968 1.54295 5.65 60.7226 88.52 0.2362 1.52525 2.87 61.5958 92.57 0.3149 1.50570 3.00 64.6855 112.49 0.3149 1.44105 3.64 University of Ghana http://ugspace.ug.edu.gh 139 68.2058 96.04 0.2362 1.37500 3.11 70.4073 62.57 0.4723 1.33731 2.03 73.0696 46.80 0.9446 1.29502 1.52 81.4833 39.49 0.6298 1.18124 1.28 Pattern List Visible Ref. Score Cpd Name Displ. Scale Chem.Formula Code [°2Th] Fac. 01-086-2334 64 Calcium Carbonate 0.000 0.739 Ca ( C O3 ) 03-065-0466 55 Silicon Oxide 0.000 0.696 Si O2 01-074-7802 33 Calcium Magnesium .. 0.000 0.695 Ca(Ca0.13Mg0.87.. 01-089-20 Potassium Sodium C.. 0.000 0.203 (K0.727 Na0.170 C.. A4: Peak and Pattern list of limestone sample EKL-R102 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 20.7131 26.69 0.4723 4.28838 0.26 23.0777 573.13 0.1181 3.85406 5.54 24.8817 99.54 0.1181 3.57857 0.96 25.8847 312.63 0.1181 3.44214 3.02 26.6572 316.09 0.1181 3.34412 3.06 27.9444 116.94 0.1574 3.19293 1.13 28.7504 219.09 0.1181 3.10522 2.12 29.4456 10343.67 0.1968 3.03348 100.00 31.4925 145.81 0.1968 2.84083 1.41 36.0192 890.85 0.1574 2.49352 8.61 39.4548 1181.59 0.1968 2.28395 11.42 42.6186 98.83 0.1968 2.12144 0.96 43.2106 1043.98 0.1968 2.09374 10.09 47.1510 294.04 0.1574 1.92755 2.84 47.5502 953.92 0.2362 1.91229 9.22 48.5445 1086.77 0.2362 1.87543 10.51 56.5793 155.05 0.1181 1.62669 1.50 57.4320 445.84 0.1574 1.60455 4.31 60.7022 302.12 0.1574 1.52571 2.92 61.5111 90.93 0.2362 1.50757 0.88 63.1353 80.47 0.3149 1.47265 0.78 64.7170 259.24 0.1968 1.44042 2.51 65.7063 104.29 0.3149 1.42111 1.01 69.2340 53.09 0.3936 1.35707 0.51 70.3721 49.94 0.4723 1.33789 0.48 72.9801 102.70 0.3149 1.29638 0.99 76.3956 34.11 0.3149 1.24671 0.33 77.2411 62.92 0.3936 1.23516 0.61 81.6010 79.97 0.3149 1.17984 0.77 83.8193 138.53 0.1968 1.15417 1.34 84.9009 56.41 0.3149 1.14221 0.55 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 01-086-2334 76 Calcium Carbonate 0.000 0.675 Ca( C O3 ) 01-081-1665 31 Silicon Oxide 0.000 0.057 Si O2 University of Ghana http://ugspace.ug.edu.gh 140 A5: Peak and Pattern list of limestone sample EKA-Y04 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 8.7857 138.26 0.4723 10.06517 0.92 19.7546 79.54 0.2362 4.49425 0.53 20.8510 432.49 0.1181 4.26033 2.89 22.0100 64.09 0.2362 4.03854 0.43 23.9567 194.68 0.1574 3.71461 1.30 26.6393 2116.28 0.1181 3.34632 14.13 27.7825 69.50 0.2362 3.21117 0.46 29.4277 805.70 0.1574 3.03528 5.38 30.7525 14972.42 0.1968 2.90748 100.00 33.3278 119.73 0.3936 2.68847 0.80 35.0405 160.98 0.3149 2.56089 1.08 36.5378 89.67 0.1968 2.45931 0.60 37.2445 279.26 0.2362 2.41425 1.87 39.4636 177.43 0.1574 2.28346 1.19 40.9211 726.92 0.2755 2.20543 4.86 42.4807 87.64 0.1574 2.12801 0.59 43.7316 56.92 0.2362 2.07000 0.38 44.7119 400.29 0.1574 2.02686 2.67 49.1599 58.90 0.2362 1.85338 0.39 50.1077 550.41 0.1574 1.82052 3.68 50.7603 583.87 0.3149 1.79864 3.90 55.1028 10.92 0.7872 1.66673 0.07 58.7317 51.87 0.3936 1.57211 0.35 59.5991 151.85 0.2362 1.55128 1.01 59.9570 182.92 0.2362 1.54288 1.22 61.7710 28.62 0.4723 1.50185 0.19 63.2300 95.63 0.4723 1.47067 0.64 64.3101 84.01 0.9446 1.44855 0.56 67.2413 111.14 0.3936 1.39236 0.74 68.2208 65.64 0.2362 1.37474 0.44 70.4225 42.73 0.6298 1.33706 0.29 72.7874 31.87 0.7085 1.29934 0.21 76.9974 26.31 0.9446 1.23846 0.18 79.8314 33.13 0.6298 1.20147 0.22 81.4034 18.47 0.4723 1.18220 0.12 87.7561 68.23 0.6298 1.11226 0.46 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 98-017-1525 57 Dolomite 0.000 0.712 C2 Ca1 Mg1 O6 01-087-2096 53 Silicon Oxide 0.000 0.140 Si O2 98-015-2200 23 Ankerite 0.000 0.649 C2 Ca1 Fe0.33 Mg0... 98-006-8547 13 Muscovite 2M1 0.000 0.023 H2 Al2.97 Fe0.03 K.. A6: Peak and Pattern list of limestone sample EKL-D01 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 23.0841 596.77 0.1181 3.85301 6.79 26.6495 744.73 0.1181 3.34507 8.47 27.9428 143.91 0.1181 3.19311 1.64 29.4406 8791.41 0.1968 3.03398 100.00 30.7558 1351.91 0.1574 2.90717 15.38 31.5028 128.89 0.2362 2.83992 1.47 34.8469 23.21 0.4723 2.57467 0.26 36.0077 822.46 0.1574 2.49429 9.36 37.3973 35.98 0.4723 2.40474 0.41 University of Ghana http://ugspace.ug.edu.gh 141 39.4512 1030.15 0.1574 2.28415 11.72 40.9351 85.06 0.2755 2.20471 0.97 43.2028 1047.24 0.1968 2.09410 11.91 44.7549 83.24 0.1574 2.02502 0.95 47.1220 255.25 0.1574 1.92867 2.90 47.5392 882.72 0.2362 1.91271 10.04 48.5415 847.98 0.2362 1.87553 9.65 50.1074 108.26 0.1574 1.82054 1.23 56.5906 127.13 0.1968 1.62640 1.45 57.4279 335.51 0.1968 1.60466 3.82 60.6981 218.37 0.1968 1.52580 2.48 63.1640 64.82 0.3149 1.47205 0.74 64.6883 238.03 0.2362 1.44100 2.71 65.7157 98.16 0.3149 1.42093 1.12 69.2500 50.16 0.2362 1.35680 0.57 70.2864 73.55 0.3149 1.33931 0.84 72.9795 81.27 0.3149 1.29639 0.92 76.3689 46.50 0.3149 1.24708 0.53 77.2558 55.62 0.3149 1.23496 0.63 81.5665 75.34 0.3936 1.18025 0.86 83.8475 107.60 0.3149 1.15385 1.22 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 01-086-2334 77 Calcium Carbonate 0.000 0.684 Ca( C O3 ) 01-070-3755 31 Silicon Oxide 0.000 0.092 Si O2 98-017-1525 40 Dolomite 0.000 0.113 C2 Ca1 Mg1 O6 A7: Peak and Pattern list of limestone sample EKL-Y03 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 6.0886 191.76 0.6298 14.51627 2.44 8.8873 287.67 0.1574 9.95036 3.66 12.2515 86.82 0.4723 7.22451 1.10 17.8134 113.60 0.2362 4.97939 1.44 19.7402 136.34 0.3149 4.49748 1.73 20.8575 641.04 0.1574 4.25901 8.15 23.0770 205.41 0.1181 3.85418 2.61 26.6484 2823.15 0.1181 3.34520 35.89 27.8676 137.51 0.2362 3.20156 1.75 29.4431 3673.48 0.1574 3.03373 46.70 30.7571 7865.73 0.1574 2.90705 100.00 33.3617 58.78 0.4723 2.68581 0.75 34.9814 139.60 0.3936 2.56508 1.77 36.0172 230.60 0.1574 2.49365 2.93 36.5450 209.40 0.1181 2.45884 2.66 37.2096 136.57 0.1968 2.41644 1.74 39.4613 521.37 0.1968 2.28359 6.63 40.9344 293.58 0.1968 2.20475 3.73 42.4540 126.80 0.1574 2.12928 1.61 43.2208 360.67 0.1574 2.09327 4.59 44.7147 214.52 0.1968 2.02675 2.73 47.5707 317.81 0.1968 1.91152 4.04 48.5622 319.12 0.1968 1.87478 4.06 50.1286 527.53 0.1574 1.81981 6.71 50.7575 247.79 0.2362 1.79873 3.15 57.4919 131.21 0.3149 1.60302 1.67 59.9965 170.45 0.2362 1.54196 2.17 61.5343 117.31 0.2362 1.50706 1.49 64.7815 85.35 0.2362 1.43915 1.09 65.7250 74.33 0.3149 1.42076 0.94 68.2469 108.98 0.3149 1.37427 1.39 72.9735 31.34 0.9446 1.29648 0.40 80.0032 32.62 0.4723 1.19933 0.41 81.5876 51.26 0.4723 1.18000 0.65 83.9750 55.29 0.4723 1.15243 0.70 University of Ghana http://ugspace.ug.edu.gh 142 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 01-087-2096 61 Silicon Oxide 0.000 0.360 Si O2 98-042-3568 57 Calcium Carbonate 0.000 0.421 C1 Ca1 O3 00-041-0586 47 Calcium Iron Magne.. 0.000 0.990 Ca(Fe+2, Mg) .. 98-007-9027 24 Muscovite 2M1 0.000 0.074 H2 Al2.82 Ba0.01 F.. A8: Peak and Pattern list of limestone sample EKL-Y01 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 8.8863 641.54 0.1181 9.95142 11.47 12.4858 112.72 0.2362 7.08951 2.02 17.7959 187.32 0.1574 4.98424 3.35 19.7498 165.68 0.3149 4.49532 2.96 20.8775 533.33 0.1181 4.25498 9.54 23.0958 409.39 0.1574 3.85108 7.32 24.2157 89.43 0.2362 3.67546 1.60 25.1366 44.30 0.5510 3.54286 0.79 26.6663 2377.87 0.1574 3.34300 42.52 27.9702 362.74 0.1181 3.19004 6.49 29.4604 5591.91 0.1574 3.03199 100.00 30.7839 524.92 0.3149 2.90459 9.39 33.1766 160.49 0.1574 2.70037 2.87 34.9652 159.26 0.3149 2.56623 2.85 36.0391 597.81 0.1574 2.49218 10.69 36.5793 140.39 0.1181 2.45661 2.51 37.5253 51.36 0.4723 2.39683 0.92 39.4694 861.53 0.1968 2.28314 15.41 40.9459 54.56 0.4723 2.20416 0.98 42.4649 140.77 0.1574 2.12877 2.52 43.2222 647.08 0.1968 2.09321 11.57 45.6361 71.93 0.4723 1.98794 1.29 47.1929 172.09 0.1181 1.92594 3.08 47.5795 638.15 0.1968 1.91119 11.41 48.5581 620.78 0.1968 1.87493 11.10 50.1414 282.62 0.1181 1.81938 5.05 54.0684 34.27 0.4723 1.69615 0.61 56.6850 105.03 0.2362 1.62391 1.88 57.4512 261.85 0.1574 1.60406 4.68 59.9713 155.02 0.1181 1.54254 2.77 60.7330 187.07 0.1574 1.52501 3.35 61.5414 106.55 0.3149 1.50690 1.91 64.0757 63.10 0.2362 1.45328 1.13 64.7074 160.52 0.1574 1.44062 2.87 65.7539 102.05 0.3936 1.42020 1.83 68.2752 99.06 0.3149 1.37377 1.77 70.3667 85.82 0.3149 1.33798 1.53 73.0082 60.21 0.6298 1.29595 1.08 81.6160 63.73 0.2362 1.17966 1.14 83.8335 117.84 0.1181 1.15401 2.11 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 01-085-0796 53 Silicon Oxide 0.000 0.430 Si O2 98-017-1524 31 Dolomite 0.000 0.094 C2 Ca1 Mg1 O6 01-086-2334 63 Calcium Carbonate 0.000 0.512 Ca( C O3 ) 98-003-4406 25 Muscovite 2M1 0.000 0.091 H4 Al5.74 Fe0.26 K.. University of Ghana http://ugspace.ug.edu.gh 143 A9: Peak and Pattern list of limestone sample EKA-R02 from XRD Analysis Peak List Pos.[°2Th.] Height [cts] FWHMLeft[°2Th.] d-spacing [Å] Rel. Int. [%] 8.7573 129.07 0.6298 10.09773 1.24 20.8955 90.42 0.1181 4.25137 0.87 23.0991 627.45 0.1574 3.85053 6.02 26.6585 481.37 0.1181 3.34396 4.62 27.9618 101.08 0.1181 3.19098 0.97 29.4547 10414.21 0.1574 3.03257 100.00 31.4897 140.85 0.1574 2.84107 1.35 36.0243 919.79 0.1968 2.49317 8.83 39.4605 1271.67 0.1968 2.28363 12.21 43.2100 1166.05 0.1968 2.09377 11.20 47.1602 301.52 0.1574 1.92719 2.90 47.5476 986.10 0.2755 1.91239 9.47 48.5468 1011.67 0.2755 1.87534 9.71 56.6115 197.14 0.1968 1.62584 1.89 57.4485 403.02 0.1574 1.60413 3.87 60.7171 266.18 0.1574 1.52537 2.56 63.1496 81.11 0.3149 1.47235 0.78 64.6966 264.47 0.2362 1.44083 2.54 65.6985 117.15 0.3149 1.42126 1.12 69.3024 35.08 0.3936 1.35590 0.34 70.3539 77.82 0.3149 1.33819 0.75 72.9498 117.43 0.1574 1.29685 1.13 76.3870 41.58 0.3149 1.24683 0.40 77.2734 68.47 0.4723 1.23472 0.66 81.5967 81.59 0.4723 1.17989 0.78 83.8584 116.68 0.3936 1.15373 1.12 84.8859 63.26 0.4723 1.14237 0.61 Pattern List Visible Score Cpd Displ. Scale Chem. Ref.Code Name [°2Th] Fac. Formula 01-086-2334 80 Calcium Carbonate 0.000 0.592 Ca( C O3 ) 01-083-2199 9 Sodium Calcium Man.. 0.000 0.021 Ca0.34 Mn1.65 Na H.. 01-078-1252 17 Silicon Oxide 0.000 0.041 Si O2 University of Ghana http://ugspace.ug.edu.gh 144 APPENDIX B: Petrographic Thin Section of limestone samples (i) : Photomicrograph of limestone samples (a) EKA-Bk03, (b) EKA-B01 and (c) EKL-R102 (ii) Photomicrograph of limestone samples (d) EKA-Y04, (e) EKL-D01 and (f) EKL-Y03 (iii) Photomicrograph of limestone samples (g) EKA-R02 a b d c f e g University of Ghana http://ugspace.ug.edu.gh 145 APPENDIX C: Activity Concentrations of Samples C1: Activity concentration of limestone sample EKA-B01 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 5562.56 0.193 36000 1.5809 0.2635 1.9218968 351.932 9830.33 0.376 36000 1.5809 0.234141 1.961982 241.997 2674.3 0.0743 36000 1.5809 0.301147 2.1000812 Bi-214 609.312 7594.95 0.461 36000 1.5809 0.161915 1.7878487 1120.287 1542.96 0.151 36000 1.5809 0.107535 1.6696348 1764.494 1277.82 0.154 36000 1.5809 0.079245 1.8398067 Th-232 series Pb-212 238.632 5467.14 0.433 36000 1.5809 0.303994 0.7297943 Tl-208 583.191 1839.99 0.845 36000 1.5809 0.166753 0.2294447 510.77 1612.14 0.226 36000 1.5809 0.182293 0.6875689 Ac-228 338.32 1186.06 0.1127 36000 1.5809 0.240431 0.7691046 911.204 1330.02 0.258 36000 1.5809 0.123548 0.733153 968.971 830.47 0.158 36000 1.5809 0.118549 0.7790444 Ra-224 240.986 2743.67 0.041 36000 1.5809 0.301995 3.8935073 K-40 K-40 1460.83 9860.68 0.11 36000 1.5809 0.089968 17.507319 C2: Activity concentration of limestone sample EKA-Bk03 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.224 1718.81 0.193 36000 1.6418 0.263485 0.571862 351.932 2965.78 0.376 36000 1.6418 0.234141 0.569967 Bi-214 609.312 2402.72 0.461 36000 1.6418 0.161915 0.544619 Th-232 series Pb-212 238.632 2130.02 0.433 36000 1.6418 0.303994 0.273784 Tl-208 510.77 1129.42 0.226 36000 1.6418 0.182293 0.463824 K-40 K-40 1460.83 3169.55 0.11 36000 1.6418 0.089968 5.418693 University of Ghana http://ugspace.ug.edu.gh 146 C3: Activity concentration of limestone sample EKA-R01 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 1395.24 0.193 36000 1.5586 0.2635 0.4889608 351.932 2433.47 0.376 36000 1.5586 0.234141 0.492632 241.997 878.86 0.0743 36000 1.5586 0.301147 0.700028 Bi-214 609.312 1834.97 0.461 36000 1.5586 0.161915 0.4381316 Th-232 series Pb-212 238.632 7491.01 0.433 36000 1.5586 0.303994 1.0142625 Tl-208 583.191 2548.45 0.845 36000 1.5586 0.166753 0.3223358 510.77 1677.75 0.226 36000 1.5586 0.182293 0.7257891 Ac-228 338.32 1348.02 0.1127 36000 1.5586 0.240431 0.8866349 911.204 1647.22 0.258 36000 1.5586 0.123548 0.9209961 968.971 1011.36 0.158 36000 1.5586 0.118549 0.9623072 Ra-224 240.986 878.86 0.041 36000 1.5586 0.301995 1.2650234 K-40 K-40 1460.83 17232.86 0.11 36000 1.5586 0.089968 31.034151 C4: Activity concentration of limestone sample EKA-R02 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 351.932 2032.87 0.376 36000 1.5778 0.234141 0.406527 Bi-214 609.312 1532.62 0.461 36000 1.5778 0.161915 0.361487 Th-232 series Pb-212 238.632 3896.18 0.433 36000 1.5778 0.303994 0.521113 Tl-208 583.191 1135.59 0.845 36000 1.5778 0.166753 0.141885 510.77 1383.08 1.226 36000 1.5778 0.182293 0.591035 K-40 K-40 1460.83 7678.66 0.11 36000 1.5778 0.089968 13.66 University of Ghana http://ugspace.ug.edu.gh 147 C5: Activity concentration of limestone sample EKA-Y04 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 5889.6 0.193 36000 1.5477 0.2635 2.078542 351.932 9819.31 0.376 36000 1.5477 0.234141 2.001822 241.997 3038.37 0.0743 36000 1.5477 0.301147 2.437161 Bi-214 609.312 8054.82 0.461 36000 1.5477 0.161915 1.936776 1120.287 1750.34 0.151 36000 1.5477 0.107535 1.93467 1764.494 1492.19 0.154 36000 1.5477 0.079245 2.194544 Th-232 series Pb-212 238.632 4420.47 0.433 36000 1.5477 0.303994 0.602735 Tl-208 583.191 1482.73 0.845 36000 1.5477 0.166753 0.188861 510.77 1614.27 0.226 36000 1.5477 0.182293 0.703246 911.204 1045.59 0.258 36000 1.5477 0.123548 0.588729 Ra-224 240.986 3038.37 0.041 36000 1.5477 0.301995 4.404204 K-40 K-40 1460.83 8053.43 0.11 36000 1.5809 0.089968 14.60533 C6: Activity concentration of limestone sample EKL-Y03 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 3770.15 0.193 36000 1.5787 0.2635 1.304424 351.932 6590.99 0.376 36000 1.5787 0.234141 1.317293 241.997 2088.97 0.0743 36000 1.5787 0.301147 1.642718 Bi-214 609.312 5102.06 0.461 36000 1.5787 0.161915 1.202697 1120.287 1075.09 0.151 36000 1.5787 0.107535 1.164975 1764.494 1020.41 0.154 36000 1.5787 0.079245 1.471235 Th-232 series Pb-212 238.632 9320.48 0.433 36000 1.5787 0.303994 1.2459 Tl-208 583.191 3065.88 0.845 36000 1.5787 0.166753 0.382845 510.77 2223.76 0.226 36000 1.5787 0.182293 0.949743 Ac-228 338.32 1856.42 0.1127 36000 1.5787 0.240431 1.205479 University of Ghana http://ugspace.ug.edu.gh 148 911.204 2162.9 0.258 36000 1.5787 0.123548 1.193927 968.971 1189.78 0.158 36000 1.5787 0.118549 1.11766 Ra-224 240.986 2066.81 0.041 36000 1.5787 0.301995 2.937071 K-40 K-40 1460.83 17831.52 0.11 36000 1.5787 0.089968 31.70341 C7: Activity concentration of limestone sample EKL-D01 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 14196.33 0.193 36000 1.4757 0.2635 5.254577 351.932 25386.36 0.376 36000 1.4757 0.234141 5.427923 241.997 7245.75 0.0743 36000 1.4757 0.301147 6.095588 Bi-214 609.312 19144.47 0.461 36000 1.4757 0.161915 4.827869 1120.287 4114.59 0.151 36000 1.4757 0.107535 4.769795 1764.494 3476.67 0.154 36000 1.4757 0.079245 5.362562 1238.11 1541.97 0.0579 36000 1.4757 0.100546 4.985771 Th-232 series Pb-212 238.632 4068.2 0.433 36000 1.4757 0.303994 0.581767 Tl-208 583.191 1307.22 0.845 36000 1.4757 0.166753 0.17463 510.77 1529.72 0.226 36000 1.4757 0.182293 0.698927 911.204 919.72 0.258 36000 1.4757 0.123548 0.543123 Ra-224 240.986 7245.75 0.041 36000 1.4757 0.301995 11.01536 K-40 K-40 1460.83 6312.86 0.11 36000 1.4757 0.089968 12.0073 University of Ghana http://ugspace.ug.edu.gh 149 C8: Activity concentration of limestone sample EKL-R102 Radionucli de Energy (kev) Net Area γ-Yield Counting Time Mass (kg) Efficiency Activity U-238 series Pb-214 295.2 1847.85 0.193 36000 1.3911 0.2635 0.725551 351.932 3254.88 0.376 36000 1.3911 0.234141 0.738258 241.997 1368 0.0743 36000 1.3911 0.301147 0.738258 Bi-214 609.312 2558.15 0.461 36000 1.3911 0.161915 1.220838 Th-232 series Tl-208 583.191 3633.63 0.845 36000 1.3911 0.166753 0.684349 510.77 2056.66 0.226 36000 1.3911 0.182293 0.514931 Ac-228 338.32 2065.82 0.1127 36000 1.3911 0.240431 0.996832 911.204 2459 0.258 36000 1.3911 0.123548 1.540427 968.971 1515.81 0.158 36000 1.3911 0.118549 1.615954 Ra-224 240.986 1369.08 0.041 36000 1.3911 0.301995 2.207923 K-40 K-40 1460.83 24482.38 0.11 36000 1.3911 0.089968 49.39835 University of Ghana http://ugspace.ug.edu.gh 150 C9: Certificate of Reference material for radiological analysis University of Ghana http://ugspace.ug.edu.gh 151 APPENDIX D: Batch Adsorption Analysis D1: % fluoride adsorption of sample EKL-R102 in 1 mg/L NaF solution. Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.003 500-1000 1.0973 0.7655 15 30.24 3.3170 10.005 500-1000 1.0973 0.6243 30 43.11 4.7286 10.002 500-1000 1.0973 0.3124 45 71.53 7.8466 10.001 500-1000 1.0973 0.4532 60 58.70 50.8931 6.4391 10.002 500-1000 1.0973 0.7213 75 34.27 3.7589 10.004 500-1000 1.0973 1.0973 90 11.34 1.2436 10.006 1000-2000 1.0973 0.7105 15 35.25 3.8668 10.004 1000-2000 1.0973 0.5871 30 46.50 5.1005 10.004 1000-2000 1.0973 0.3257 45 70.32 57.2724 7.7137 10.002 1000-2000 1.0973 0.2521 60 77.03 8.4495 10.001 1000-2000 1.0973 1.0102 75 7.94 0.8707 10.004 1000-2000 1.0973 1.0509 90 4.23 0.4639 10.001 2000-6350 1.0973 0.5217 15 52.46 5.7543 10.000 2000-6350 1.0973 0.6732 30 38.65 4.2397 10.003 2000-6350 1.0973 0.7852 45 28.44 32.9422 3.1201 10.003 2000-6350 1.0973 0.9632 60 12.22 1.3406 10.006 2000-6350 1.0973 1.0038 75 8.52 0.9347 10.004 2000-6350 1.0973 1.0021 90 8.68 0.9517 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.004 500-1000 1.0973 0.8442 15 23.07 2.5302 50.002 500-1000 1.0973 0.6875 30 37.35 4.0968 50.004 500-1000 1.0973 0.6373 45 41.92 4.5986 50.003 500-1000 1.0973 0.3487 60 68.22 42.6387 7.4838 50.001 500-1000 1.0973 0.8423 75 23.24 2.5492 50.002 500-1000 1.0973 0.9321 90 15.06 1.6515 50.006 1000-2000 1.0973 0.7329 15 33.21 3.6429 50.004 1000-2000 1.0973 0.6285 30 42.72 4.6866 50.002 1000-2000 1.0973 0.4502 45 58.97 44.6573 6.4691 50.001 1000-2000 1.0973 0.6175 60 43.73 4.7966 50.002 1000-2000 1.0973 0.8761 75 20.16 2.2113 50.002 1000-2000 1.0973 1.0010 90 8.78 0.9627 50.002 2000-6350 1.0973 0.6551 15 40.30 4.4207 50.004 2000-6350 1.0973 0.6212 30 43.39 4.7596 50.004 2000-6350 1.0973 0.5471 45 50.14 47.0222 5.5003 50.001 2000-6350 1.0973 0.5019 60 54.26 5.9522 50.005 2000-6350 1.0973 0.8563 75 21.96 2.4093 50.003 2000-6350 1.0973 0.9728 90 11.35 1.2446 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.000 500-1000 1.0973 0.8442 15 23.07 2.5302 100.002 500-1000 1.0973 0.6875 30 37.35 4.0968 100.003 500-1000 1.0973 0.6373 45 41.92 4.5986 100.001 500-1000 1.0973 0.3487 60 68.22 42.6387 7.4838 100.006 500-1000 1.0973 0.8423 75 23.24 2.5492 100.007 500-1000 1.0973 0.9321 90 15.06 1.6515 100.004 1000-2000 1.0973 0.7329 15 33.21 3.6429 University of Ghana http://ugspace.ug.edu.gh 152 100.005 1000-2000 1.0973 0.6285 30 42.72 4.6866 100.002 1000-2000 1.0973 0.4502 45 58.97 44.6573 6.4691 100.003 1000-2000 1.0973 0.6175 60 43.73 4.7966 100.005 1000-2000 1.0973 0.8761 75 20.16 2.2113 100.007 1000-2000 1.0973 1.0010 90 8.78 0.9627 100.002 2000-6350 1.0973 0.6551 15 40.30 4.4207 100.004 2000-6350 1.0973 0.6212 30 43.39 4.7596 100.001 2000-6350 1.0973 0.5471 45 50.14 47.0222 5.5003 100.001 2000-6350 1.0973 0.5019 60 54.26 5.9522 100.003 2000-6350 1.0973 0.8563 75 21.96 2.4093 100.001 2000-6350 1.0973 0.9728 90 11.35 1.2446 D2: % fluoride adsorption of sample EKL-R102 in 5 mg/L NaF solution Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.002 500-1000 5.0506 3.4666 15 31.84 15.8368 10.001 500-1000 5.0506 2.9810 30 40.98 20.6919 10.003 500-1000 5.0506 2.3066 45 54.33 27.4345 10.004 500-1000 5.0506 1.3547 60 73.18 49.96 36.9516 10.002 500-1000 5.0506 2.7413 75 45.72 23.0883 10.000 500-1000 5.0506 4.4356 90 12.18 6.1488 10.002 1000-2000 5.0506 4.1849 15 17.14 8.6552 10.001 1000-2000 5.0506 2.6734 30 47.07 23.7672 10.000 1000-2000 5.0506 2.2037 45 56.37 45.37 28.4633 10.000 1000-2000 5.0506 1.9748 60 60.90 30.7518 10.003 1000-2000 5.0506 2.3972 75 52.54 26.5286 10.004 1000-2000 5.0506 2.0739 90 58.94 29.7610 10.002 2000-6350 5.0506 2.7840 15 44.88 10.001 2000-6350 5.0506 3.7496 30 25.76 22.6615 10.003 2000-6350 5.0506 3.9334 45 22.12 25.64 13.0074 10.000 2000-6350 5.0506 4.5555 60 9.80 11.1698 10.000 2000-6350 5.0506 3.7726 75 25.30 4.9500 10.004 2000-6350 5.0506 2.0534 90 59.34 29.9660 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.003 500-1000 5.0506 2.6712 15 47.11 23.7892 50.001 500-1000 5.0506 2.5713 30 49.09 24.7880 50.001 500-1000 5.0506 2.1127 45 58.17 29.3731 50.003 500-1000 5.0506 1.7436 60 65.48 54.96 33.0634 50.000 500-1000 5.0506 3.6812 75 27.11 13.6913 50.005 500-1000 5.0506 3.9084 90 22.62 11.4197 50.005 1000-2000 5.0506 2.4247 15 51.99 26.2537 50.002 1000-2000 5.0506 2.2542 30 55.37 27.9584 50.000 1000-2000 5.0506 1.6272 45 67.78 62.96 34.2272 50.006 1000-2000 5.0506 1.1773 60 76.69 38.7253 50.000 1000-2000 5.0506 3.9911 75 20.98 10.5929 50.000 1000-2000 5.0506 3.2791 90 35.08 17.7115 50.002 2000-6350 5.0506 2.5710 15 49.10 24.7910 50.001 2000-6350 5.0506 3.7994 30 24.77 12.5095 50.000 2000-6350 5.0506 3.5678 45 29.36 34.66 14.8250 50.000 2000-6350 5.0506 3.2614 60 35.43 17.8884 50.003 2000-6350 5.0506 3.5417 75 29.88 15.0860 50.000 2000-6350 5.0506 3.2978 90 34.70 17.5245 University of Ghana http://ugspace.ug.edu.gh 153 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.003 500-1000 5.0506 3.8411 15 23.95 12.0926 100.002 500-1000 5.0506 3.4149 30 32.39 16.3537 100.000 500-1000 5.0506 3.5173 45 30.36 15.3299 100.005 500-1000 5.0506 3.7349 60 26.05 28.19 13.1544 100.000 500-1000 5.0506 2.0094 75 60.21 30.4059 100.000 500-1000 5.0506 3.0998 90 38.63 19.5041 100.002 1000-2000 5.0506 3.3606 15 33.46 16.8966 100.004 1000-2000 5.0506 2.3515 30 53.44 26.9856 100.000 1000-2000 5.0506 2.2386 45 55.68 50.44 28.1144 100.000 1000-2000 5.0506 2.0613 60 59.19 29.8870 100.007 1000-2000 5.0506 2.6714 75 47.11 23.7872 100.000 1000-2000 5.0506 2.9827 90 40.94 20.6749 100.002 2000-6350 5.0506 4.7412 15 6.13 3.0934 100.004 2000-6350 5.0506 4.1127 30 18.57 9.3771 100.000 2000-6350 5.0506 3.6824 45 27.09 20.22 13.6793 100.004 2000-6350 5.0506 3.5814 60 29.09 14.6891 100.000 2000-6350 5.0506 3.8410 75 23.95 12.0963 100.001 2000-6350 5.0506 3.5515 90 29.68 14.9880 D3: % fluoride adsorption of sample EKL-R102 in 10 mg/L NaF solution. Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.003 500-1000 10.1726 6.0761 15 40.27 40.9568 10.005 500-1000 10.1726 5.6827 30 44.14 44.8945 10.002 500-1000 10.1726 5.6221 45 44.73 45.4914 10.001 500-1000 10.1726 4.0029 60 60.65 47.4476 61.6723 10.002 500-1000 10.1726 7.7931 75 23.39 23.7902 10.004 500-1000 10.1726 8.8365 90 13.13 13.3610 10.006 1000-2000 10.1726 6.8015 15 33.14 33.7043 10.004 1000-2000 10.1726 6.4512 30 36.58 37.2103 10.004 1000-2000 10.1726 5.6719 45 44.24 40.7637 45.0070 10.002 1000-2000 10.1726 5.1789 60 49.09 49.9370 10.001 1000-2000 10.1726 6.5058 75 36.05 36.6570 10.004 1000-2000 10.1726 8.8312 90 13.19 13.4086 10.001 2000-6350 10.1726 6.6754 15 34.38 34.9650 10.000 2000-6350 10.1726 6.6298 30 34.83 35.4245 10.003 2000-6350 10.1726 5.0143 45 50.71 39.7932 51.5675 10.003 2000-6350 10.1726 6.1789 60 39.26 39.9370 10.006 2000-6350 10.1726 6.9995 75 31.19 31.7310 10.004 2000-6350 10.1726 8.4802 90 16.64 16.9172 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.004 500-1000 10.1726 6.2541 15 38.52 7.8365 50.002 500-1000 10.1726 5.9027 30 41.97 8.5396 50.004 500-1000 10.1726 5.2584 45 48.31 9.8282 50.003 500-1000 10.1726 4.5077 60 55.69 46.1227 11.3291 50.001 500-1000 10.1726 7.6603 75 24.70 5.0246 50.002 500-1000 10.1726 8.4207 90 17.22 3.5034 50.006 1000-2000 10.1726 6.0344 15 40.68 8.2756 50.004 1000-2000 10.1726 5.3942 30 46.97 9.5564 University of Ghana http://ugspace.ug.edu.gh 154 50.002 1000-2000 10.1726 4.4393 45 56.36 50.9624 11.4666 50.001 1000-2000 10.1726 4.0857 60 59.84 12.1723 50.002 1000-2000 10.1726 7.4160 75 27.10 5.5132 50.002 1000-2000 10.1726 8.4197 90 17.23 3.5058 50.002 2000-6350 10.1726 6.9566 15 31.61 6.4317 50.004 2000-6350 10.1726 6.2906 30 38.16 7.7638 50.004 2000-6350 10.1726 5.0797 45 50.06 36.4287 10.1858 50.001 2000-6350 10.1726 7.5405 60 25.87 5.2642 50.005 2000-6350 10.1726 7.3408 75 27.84 5.6632 50.003 2000-6350 10.1726 8.0572 90 20.80 4.2308 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.000 500-1000 10.1726 6.0291 15 40.73 4.1434 100.002 500-1000 10.1726 5.5775 30 45.17 4.5950 100.003 500-1000 10.1726 4.7422 45 53.38 5.4304 100.001 500-1000 10.1726 4.1481 60 59.22 49.6272 6.0242 100.006 500-1000 10.1726 7.7651 75 23.67 2.4075 100.007 500-1000 10.1726 9.1726 90 9.83 1.0000 100.004 1000-2000 10.1726 6.6003 15 35.12 3.5722 100.005 1000-2000 10.1726 5.8207 30 42.78 4.3517 100.002 1000-2000 10.1726 5.0113 45 50.74 45.2293 5.1613 100.003 1000-2000 10.1726 4.8541 60 52.28 5.3185 100.005 1000-2000 10.1726 6.9612 75 31.57 3.2212 100.007 1000-2000 10.1726 8.9621 90 11.90 1.2105 100.002 2000-6350 10.1726 6.3789 15 37.29 3.7936 100.004 2000-6350 10.1726 5.8219 30 42.77 4.3505 100.001 2000-6350 10.1726 5.2904 45 47.99 43.9806 4.8822 100.001 2000-6350 10.1726 5.3033 60 47.87 4.8691 100.003 2000-6350 1.0973 7.6533 75 24.77 2.5193 100.001 2000-6350 1.0973 8.8235 90 13.26 1.3491 D4: % fluoride adsorption of sample EKL-D01 in 1 mg/L NaF solution Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.003 500-1000 1.0230 1.0010 15 2.15 0.2200 10.005 500-1000 1.0230 0.8672 30 15.23 1.5577 10.002 500-1000 1.0230 0.5902 45 42.31 4.3271 10.001 500-1000 1.0230 0.4721 60 53.85 28.3847 5.5079 10.002 500-1000 1.0230 0.6453 75 36.92 3.7762 10.004 500-1000 1.0230 0.9783 90 4.37 0.4469 10.006 1000-2000 1.0230 0.9871 15 3.51 0.3589 10.004 1000-2000 1.0230 0.8372 30 18.16 1.8576 10.004 1000-2000 1.0230 0.5439 45 46.83 4.3271 10.002 1000-2000 1.0230 0.4329 60 57.68 31.5469 5.5079 10.001 1000-2000 1.0230 1.6734 75 34.17 3.7762 10.004 1000-2000 1.0230 0.8217 90 19.68 2.0126 10.001 2000-6350 1.0230 1.0080 15 1.47 0.1500 10.000 2000-6350 1.0230 0.9782 30 4.38 0.4479 10.003 2000-6350 1.0230 0.7329 45 28.36 16.1364 2.9004 10.003 2000-6350 1.0230 0.7126 60 30.34 3.1034 10.006 2000-6350 1.0230 1.8267 75 19.19 1.9626 10.004 2000-6350 1.0230 0.9864 90 3.58 0.3559 University of Ghana http://ugspace.ug.edu.gh 155 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.004 500-1000 1.0230 0.9943 15 2.81 0.2869 50.002 500-1000 1.0230 0.5481 30 46.42 4.7481 50.004 500-1000 1.0230 0.6750 45 34.02 3.4793 50.003 500-1000 1.0230 0.5298 60 48.21 32.8641 4.9310 50.001 500-1000 1.0230 0.7851 75 23.26 2.3785 50.002 500-1000 1.0230 1.0154 90 0.74 0.0760 50.006 1000-2000 1.0230 0.9431 15 7.81 0.7988 50.004 1000-2000 1.0230 0.7593 30 25.78 2.6365 50.002 1000-2000 1.0230 0.6581 45 35.67 27.2776 3.6483 50.001 1000-2000 1.0230 0.6153 60 39.85 4.0762 50.002 1000-2000 1.0230 0.7359 75 28.06 2.8704 50.002 1000-2000 1.0230 0.8761 90 14.36 1.4687 50.002 2000-6350 1.0230 0.8621 15 15.73 1.6087 50.004 2000-6350 1.0230 0.8218 30 19.67 2.0116 50.004 2000-6350 1.0230 0.6541 45 36.06 24.5552 3.6883 50.001 2000-6350 1.0230 0.7492 60 26.76 2.7375 50.005 2000-6350 1.0230 0.8789 75 14.09 1.4407 50.003 2000-6350 1.0230 1.0032 90 1.94 0.1980 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.000 500-1000 1.0230 0.8961 15 1.27 1.2687 100.002 500-1000 1.0230 0.7654 30 2.58 2.5755 100.003 500-1000 1.0230 0.7432 45 2.80 2.7974 100.001 500-1000 1.0230 0.8380 60 1.85 20.7551 1.8496 100.006 500-1000 1.0230 0.7201 75 3.03 3.0284 100.007 500-1000 1.0230 0.9126 90 1.10 1.1038 100.004 1000-2000 1.0230 0.8756 15 1.47 1.4737 100.005 1000-2000 1.0230 0.8219 30 2.01 2.0106 100.002 1000-2000 1.0230 0.7651 45 2.58 24.1544 2.5785 100.003 1000-2000 1.0230 0.6410 60 3.82 3.8192 100.005 1000-2000 1.0230 0.8616 75 1.61 1.6137 100.007 1000-2000 1.0230 0.9128 90 1.10 1.1018 100.002 2000-6350 1.0230 0.8812 15 1.42 1.4177 100.004 2000-6350 1.0230 0.8127 30 2.10 2.1026 100.001 2000-6350 1.0230 0.7219 45 3.01 23.6022 3.0104 100.001 2000-6350 1.0230 0.7104 60 3.13 3.1254 100.003 2000-6350 1.0230 0.8903 75 1.33 1.3267 100.001 2000-6350 1.0230 0.9921 90 0.31 0.3089 D5: % fluoride adsorption of sample EKL-D01 in 5 mg/L NaF solution. Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.003 500-1000 4.9561 3.8412 15 22.50 11.1468 10.005 500-1000 4.9561 3.7364 30 24.61 12.1946 10.002 500-1000 4.9561 3.8122 45 23.08 11.4367 10.001 500-1000 4.9561 2.6513 60 46.50 29.1726 23.0434 10.002 500-1000 4.9561 3.5593 75 28.18 13.9652 10.004 500-1000 4.9561 4.1582 90 16.10 7.9774 10.006 1000-2000 4.9561 4.6521 15 6.13 3.0394 10.004 1000-2000 4.9561 3.0948 30 37.56 18.6093 University of Ghana http://ugspace.ug.edu.gh 156 10.004 1000-2000 4.9561 2.8264 45 42.97 32.5352 21.2927 10.002 1000-2000 4.9561 2.8012 60 43.48 21.5447 10.001 1000-2000 4.9561 4.6231 75 6.72 3.3293 10.004 1000-2000 4.9561 4.8731 90 1.67 0.8298 10.001 2000-6350 4.9561 4.8391 15 2.36 1.1698 10.000 2000-6350 4.9561 3.7859 30 23.61 11.6997 10.003 2000-6350 4.9561 2.2799 45 54.00 37.5391 26.7566 10.003 2000-6350 4.9561 1.4776 60 70.19 34.7780 10.006 2000-6350 4.9561 3.0795 75 37.86 18.7622 10.004 2000-6350 4.9561 4.6867 90 5.44 2.6935 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.004 500-1000 4.9561 3.9283 15 20.74 10.2759 50.002 500-1000 4.9561 3.3567 30 32.27 15.9908 50.004 500-1000 4.9561 2.2835 45 53.93 26.7207 50.003 500-1000 4.9561 2.1373 60 56.88 40.9526 28.1824 50.001 500-1000 4.9561 3.9061 75 21.19 10.4979 50.002 500-1000 4.9561 4.1822 90 15.62 7.7375 50.006 1000-2000 4.9561 3.9065 15 21.18 10.4939 50.004 1000-2000 4.9561 3.3911 30 31.58 15.6469 50.002 1000-2000 4.9561 3.1288 45 36.87 36.6937 18.2693 50.001 1000-2000 4.9561 2.1237 60 57.15 28.3183 50.002 1000-2000 4.9561 2.7422 75 44.67 22.1346 50.002 1000-2000 4.9561 4.5833 90 7.52 3.7273 50.002 2000-6350 4.9561 4.7546 15 4.07 2.0146 50.004 2000-6350 4.9561 4.3074 30 13.09 6.4857 50.004 2000-6350 4.9561 4.1918 45 15.42 14.5770 7.6415 50.001 2000-6350 4.9561 3.6808 60 25.73 12.7504 50.005 2000-6350 4.9561 3.9079 75 21.15 10.4799 50.003 2000-6350 4.9561 4.3884 90 11.45 5.6759 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.000 500-1000 4.9561 4.4688 15 9.83 4.8720 100.002 500-1000 4.9561 3.7352 30 24.63 12.2066 100.003 500-1000 4.9561 2.9127 45 41.23 20.4299 100.001 500-1000 4.9561 2.7571 60 44.37 30.0165 21.9856 100.006 500-1000 4.9561 3.5452 75 28.47 14.1062 100.007 500-1000 4.9561 4.4587 90 10.04 4.9730 100.004 1000-2000 4.9561 4.8754 15 1.63 0.8068 100.005 1000-2000 4.9561 4.4201 30 10.81 5.3589 100.002 1000-2000 4.9561 3.8541 45 22.24 15.9314 11.0178 100.003 1000-2000 4.9561 3.5165 60 29.05 14.3931 100.005 1000-2000 4.9561 4.7611 75 3.93 1.9496 100.007 1000-2000 4.9561 4.8897 90 1.34 0.6639 100.002 2000-6350 4.9561 4.4460 15 10.29 5.0910 100.004 2000-6350 4.9561 3.7315 30 24.71 12.2436 100.001 2000-6350 4.9561 3.9839 45 19.62 18.9463 9.7201 100.001 2000-6350 4.9561 3.9070 60 21.17 10.4889 100.003 2000-6350 4.9561 4.3410 75 12.41 6.1498 100.001 2000-6350 4.9561 4.6063 90 7.06 3.4973 University of Ghana http://ugspace.ug.edu.gh 157 D6: % fluoride adsorption of sample EKL-D01 in 10 mg/L NaF solution. Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 10.003 500-1000 9.9518 6.6468 15 33.21 33.0434 10.005 500-1000 9.9518 4.4742 30 55.04 54.7705 10.002 500-1000 9.9518 4.2127 45 57.67 57.3738 10.001 500-1000 9.9518 7.8339 60 21.28 41.8005 21.1705 10.002 500-1000 9.9518 8.2214 75 17.39 17.3005 10.004 500-1000 9.9518 8.5614 90 13.97 13.9040 10.006 1000-2000 9.9518 6.4541 15 35.15 34.9700 10.004 1000-2000 9.9518 6.2194 30 37.50 37.3203 10.004 1000-2000 9.9518 5.4867 45 44.87 41.2458 44.6510 10.002 1000-2000 9.9518 5.2282 60 47.46 47.2360 10.001 1000-2000 9.9518 7.9727 75 19.89 19.7851 10.004 1000-2000 9.9518 9.5082 90 4.46 4.4342 10.001 2000-6350 9.9518 8.6150 15 13.43 13.3653 10.000 2000-6350 9.9518 8.4017 30 15.58 15.4994 10.003 2000-6350 9.9518 8.1342 45 18.26 17.7317 18.1705 10.003 2000-6350 9.9518 7.5978 60 23.65 23.5400 10.006 2000-6350 9.9518 7.9544 75 20.07 19.9740 10.004 2000-6350 9.9518 8.8241 90 11.33 11.2725 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 50.004 500-1000 9.9518 6.3917 15 35.77 7.1198 50.002 500-1000 9.9518 6.4882 30 34.80 6.9271 50.004 500-1000 9.9518 6.2341 45 37.36 7.4353 50.003 500-1000 9.9518 8.1552 60 18.05 31.4968 3.5930 50.001 500-1000 9.9518 8.8471 75 11.10 2.2094 50.002 500-1000 9.9518 8.6941 90 12.64 2.5151 50.006 1000-2000 9.9518 6.1153 15 38.55 7.6722 50.004 1000-2000 9.9518 6.0360 30 39.35 7.8313 50.002 1000-2000 9.9518 6.3671 45 36.02 35.5134 7.1694 50.001 1000-2000 9.9518 7.1519 60 28.13 5.5991 50.002 1000-2000 9.9518 8.9554 75 10.01 1.9928 50.002 1000-2000 9.9518 9.7098 90 2.43 0.4840 50.002 2000-6350 9.9518 6.9624 15 30.04 5.9786 50.004 2000-6350 9.9518 6.2725 30 36.97 7.3585 50.004 2000-6350 9.9518 6.3465 45 36.23 36.6682 7.2106 50.001 2000-6350 9.9518 5.6292 60 43.44 8.6452 50.005 2000-6350 9.9518 8.7203 75 12.37 2.4629 50.003 2000-6350 9.9518 9.3905 90 5.64 1.1226 Mass of sample (g) Particle size (μm) Initial F- Conc measured[Co] (mg/L) Residual F- Conc[Ct] (mg/L) Time (min) % Adsorption % Mean Adsorption (first 60th min) Adsorption capacity 100.000 500-1000 9.9518 6.2595 15 37.10 3.6922 100.002 500-1000 9.9518 4.9290 30 50.47 5.0227 100.003 500-1000 9.9518 4.7901 45 51.87 5.1617 100.001 500-1000 9.9518 4.4943 60 54.84 48.5699 5.4572 100.006 500-1000 9.9518 8.6902 75 12.68 1.2616 100.007 500-1000 9.9518 9.6541 90 2.99 0.2977 100.004 1000-2000 9.9518 5.3004 15 46.74 4.6513 100.005 1000-2000 9.9518 4.4186 30 55.60 5.5330 100.002 1000-2000 9.9518 4.4015 45 55.77 50.6810 5.5503 100.003 1000-2000 9.9518 5.5120 60 44.61 4.4398 100.005 1000-2000 9.9518 7.7804 75 21.82 2.1712 University of Ghana http://ugspace.ug.edu.gh 158 100.007 1000-2000 9.9518 8.9122 90 10.45 1.0396 100.002 2000-6350 9.9518 6.4798 15 34.89 3.4719 100.004 2000-6350 9.9518 5.9819 30 39.89 3.9697 100.001 2000-6350 9.9518 5.3254 45 46.49 41.5184 4.6264 100.001 2000-6350 9.9518 5.4928 60 44.81 4.4588 100.003 2000-6350 9.9518 8.7283 75 12.29 1.2235 100.001 2000-6350 9.9518 9.3535 90 6.01 0.5983 APPENDIX E: Preparation of NaF solutions E1: Preparation of Stock Anhydrous NaF Solution (100 mg/L) From the formula; Concentration, C, = 𝐴𝑛𝑜𝑢𝑛𝑡 𝑜𝑓 𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒 𝑉𝑜𝑙𝑢𝑚𝑒 (3) Amount of substance, n = 𝑚𝑎𝑠𝑠 𝑀𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 (4) Putting the two equations together, we have; Mass of substance, m = C × M × V Where; C = 100 mgF-/L M = 41.99 g/mol (22.990 + 18.998) V = 1000 cm3 or 1dm3 or 1L 1ppm ≡ 1 mg/L; therefore, 1000 ppm/F = 1000 mg/F- % F- in NaF = 18.998 41.988 × 100 = 45.25% 100 mg/F- = 45.25 × χ mg of NaF χ mg of NaF = 100 𝑚𝑔/𝐹 45.25/100 = 220.99 mg ≡ 0.221g University of Ghana http://ugspace.ug.edu.gh 159 E2: Preparation of Diluted Anhydrous NaF Solution (1, 5 and 10 mg/L) From the relation, C1 × V1 = C2 × V2 (5) Where; C1 = Initial Concentration of solution C2 = Final Concentration of solution V1 = Initial Volume of solution V2 = Final Volume of solution For a concentration of 1 mgF-/L; V1 = 𝐶2 × 𝑉2 𝐶1 = 1 𝑚𝑔 ×1000 𝑐𝑚3 100 𝑚𝑔 = 10cm3 For a concentration of 5 mgF-/L; V1 = 𝐶2 × 𝑉2 𝐶1 = 5 𝑚𝑔 ×1000 𝑐𝑚3 100 𝑚𝑔 = 50cm3 For a concentration of 10 mgF-/L; V1 = 𝐶2 × 𝑉2 𝐶1 = 10 𝑚𝑔 ×1000 𝑐𝑚3 100 𝑚𝑔 = 100cm3 University of Ghana http://ugspace.ug.edu.gh 160 APPENDIX F: Ion Chromatography Ion Chromatography Principle Water sample is injected into a stream of Carbonate-Bicarbonate (Na2CO3/NaHCO3) eluent and passed through a series of ion exchangers. The pressure transducer measures the system pressure at the point that the eluent flows from the pump head outlet valve into the pressure transducer. The compressor aids in cooling the system as it makes use of air (nitrogen gas) drawn from the surroundings. The anions of interest are separated on the basis of their relative affinities for a low capacity, strongly basic anion exchanger (guard and separator columns). The separated anions are directed onto a micro-membrane suppressor bathed in continuously flowing strongly acid solution (Regenerant solution). In the suppressor, the separated anions are converted to their highly conductive acid forms and the Carbonate-Bicarbonate eluent is converted to weakly conductive carbonic acid. The separated anions in their acid forms are measured by conductivity. They are identified on the basis of retention time as compared to standards. Quantitative analysis is by measuring the peak area or height. University of Ghana http://ugspace.ug.edu.gh 161 APPENDIX G: Standard Calibration Curve APPENDIX G1: Magnesium (Mg) Calibration graph APPENDIX G2: Arsenic Calibration Curve APPENDIX G3: Energy Calibration Curve y = 1.3324x - 5E-05 R² = 1 -0.2 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 M e an A b so rb an ce Mg Std Conc (mg/L) Mean Absorbance Mean Absorbancr Linear (Mean Absorbancr) y = 0.5635x - 0.0005 R² = 0.9997 0 0.01 0.02 0.03 0.04 0.05 0.06 0 0.05 0.1 0.15 M e an A b so rb an ce As Std Conc (mg/L) Mean Abs Mean Abs Linear (Mean Abs) Linear (Mean Abs) y = 1.3199x - 1.901 R² = 0.9999 0 200 400 600 800 1000 1200 1400 1600 0 200 400 600 800 1000 1200 E n er g y /k eV Channel Number University of Ghana http://ugspace.ug.edu.gh 162 APPENDIX G4: Efficiency Calibration Curve y = 1.2388x-0.68 R² = 0.9947 0 0.01 0.02 0.03 0.04 0.05 0 500 1000 1500 2000 Ef fi ci e n cy Energy (keV) Calibration Curve Eff Power (Eff) University of Ghana http://ugspace.ug.edu.gh 163 APPENDIX H: Batch Adsorption Analysis APPENDIX H1: Results of comparing anions in water samples before and after column adsorption experiment Parameters Sample Conc. Before Column Analysis (mg/L) Height of Mini-Column bed (cm) Volume of Mini-bed Column (cm3) Mass of Adsorbent in Mini-bed Column (g) Residual Conc. After Column Analysis (mg/L) Mean % Adsorption Time Aliquots Were Taken (Mins) 15 30 45 60 75 90 BNN8 7.4781 20 251.20 217.751 2.7823 2.2985 1.1324 1.5782 1.7277 1.7790 74.82 30 376.80 314.255 1.1981 2.0446 2.4526 1.6432 1.3714 1.1278 78.07 40 502.40 433.939 0.2757 1.1477 1.5454 1.1093 1.1126 1.1317 85.91 F- BNB6 6.1519 20 251.20 217.751 0.1301 1.8796 2.3876 1.953 1.8199 1.8036 72.98 30 376.80 314.255 1.8430 2.1726 1.8161 1.8701 2.2370 2.0385 67.55 40 502.40 433.939 1.5870 2.7897 3.0878 2.6451 3.0074 1.9722 59.12 Cl- BNN8 18.9343 20 251.20 217.751 16.7032 14.0901 18.8629 15.8085 16.6779 18.2356 11.64 30 376.80 314.255 13.2707 16.8549 17.3673 18.9034 16.1215 15.3839 13.82 40 502.40 433.939 16.6105 13.0259 12.1327 16.0445 18.4893 16.4069 18.39 BNB6 8.8715 20 251.20 217.751 8.1378 7.0772 8.0666 8.1196 6.5803 7.5403 14.48 30 376.80 314.255 8.2117 8.1851 7.7532 7.1327 6.3294 6.5494 17.03 40 502.40 433.939 8.7865 6.0071 7.5743 7.4426 7.9043 7.9394 14.23 NO3- BNN8 80.4559 20 251.20 217.751 28.7064 32.8647 27.3536 24.7882 24.1629 34.8897 64.21 30 376.80 314.255 29.7397 15.6413 31.4220 34.0818 34.4705 36.3429 62.36 40 502.40 433.939 25.5516 26.8257 78.3549 32.9186 39.0939 38.7698 49.97 BNB6 36.8015 20 251.20 217.751 27.7043 32.128 35.1536 30.5353 32.8512 23.2942 17.73 University of Ghana http://ugspace.ug.edu.gh 164 30 376.80 314.255 35.0923 27.1781 30.4703 29.0818 19.9655 32.5311 21.05 40 502.40 433.939 23.8601 23.703 28.8075 26.2261 24.2955 20.3841 33.30 SO42- BNN8 10.2861 20 251.20 217.751 2.8536 6.8647 6.8606 6.4488 6.8412 6.3917 41.25 30 376.80 314.255 8.2130 8.2636 9.4456 9.7939 9.9944 10.0075 9.72 40 502.40 433.939 9.8229 9.6488 8.3678 8.5674 10.0069 10.0477 8.51 BNB6 51.9879 20 251.20 217.751 18.3589 16.407 1.6289 7.8591 8.3354 15.1713 78.28 30 376.80 314.255 14.8643 4.6441 9.5094 28.6418 28.9672 30.2819 62.52 40 502.40 433.939 46.0773 8.5346 7.4508 1.5188 10.2983 14.1865 71.77 PO43- BNN8 <0.001 20 251.20 217.751 2.2523 2.0523 0.0878 0.0102 0.0131 0.0061 30 376.80 314.255 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 40 502.40 433.939 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 BNB6 0.014 20 251.20 217.751 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 30 376.80 314.255 0.021 <0.001 0.9012 1.111 <0.001 <0.001 40 502.40 433.939 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 University of Ghana http://ugspace.ug.edu.gh