Theses

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A long essay or dissertation or thesis involving personal research, written by postgraduates of University of Ghana for a university degree.

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    Synthesis andApplication of Fe-Doped TiO2-Halloysite Nanotubes Composite and Their Potential Application in Water Treatment
    (Advances in Materials Science and Engineering, 2019) Nyankson, E.; Agyei-Tuffour, B.; Adjasoo, J.; et al.
    In this work, the potential application of TiO2-Fe-HNT photocatalyst-adsorbent composite in water treatment technologies was confirmed. ,e photocatalyst-adsorbent composite (TiO2-Fe-HNTs) was synthesized by the hydrothermal method and characterized by X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron mi croscopy-energy dispersive X-ray spectroscopy, and diffuse reflectance spectroscopy. ,e adsorption and photocatalysis mechanism by the TiO2-Fe-HNT composite were examined on methylene blue dye, rhodamine blue dye, naproxen sodium (pharmaceutical drug waste), and imidacloprid (pesticide). ,e TiO2-Fe-HNT composite was active in UV and visible regions of the electromagnetic spectrum. ,e adsorption and photocatalytic efficiency increased with increasing amounts of HNTs. ,e photocatalyst-adsorbent composite exhibited excellent removal efficiency for pharmaceutical waste (naproxen sodium) and pesticides (imidacloprid). An adsorption equilibrium data fitted well with the pseudo-second-order kinetics for both methylene blue and rhodamine blue dyes with the intraparticle model describing its rate-controlling steps. ,e Langmuir and Freundlich isotherm models further described the adsorption of methylene blue and rhodamine blue molecules, respectively.
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    Comparative analyses of rice husk cellulose fiber and kaolin particulate reinforced thermoplastic cassava starch biocomposites using the solution casting technique
    (Polymer Composites, 2021) Agyei-Tuffour, B.; Asante, J.T.; Nyankson, E.; et al.
    The potential of biodegradable packaging materials from thermoplastic cassava starch (TPS) reinforced with rice husk cellulose fibers (RHCF) and kaolin particu lates (KP) using the solution casting method has been presented. This involved the blending of TPS and RHCF/KP in a plasticizer of ~4 ml of glycerol and ~45 ml of distilled water at 125 C and stirred at 60 rpm until a gel was formed. The gel was cast into sheets and bone-shaped tensile specimens and allowed to dry for 5 days and characterized. The results show a semicrystalline structure for TPS with a ~36% increase in crystallinity after reinforcement. The O-H bond stretching and the C-H bending bonds due to starch–glycerol reactions were the common functional groups in TPS–RHCF biocomposites, and Si-O-C bonds were characteristics of the silica phase in the kaolin. The water vapor transmission rate (WVTR) reduced to ~34% with KP reinforcements from ~238 g/m.day to 177 g/m. day and to ~74 g/m.day and ~164% for TPS–RHCF. The strength increased with up to 50 wt% kaolin content; ~0.96 MPa yield strength and ~2.60 MPa ultimate tensile strength (UTS) were recorded. For the RHCF reinforced composites, TPS 50 wt% also showed high strengths of ~0.96 MPa yield strength and ~3.50 MPa UTS. The WVTR reduced as the content of kaolin was increased. Typically, from 0 to 30 wt% volume fraction of kaolin, the WVTR was reduced by ~34% to 177 g/m. day for TPS–kaolin and by ~164% to ~74 g/m.day in TPS–RHCF. The as-prepared biocomposites have the potential as good packaging materials.
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    Characteristics Of Stabilized Shrink-Swell Deposits Using Eggshell Powder
    (2013) Nyankson, E.; Agyei-Tuffour, B.; Annan, E.; et al.
    Shrink-swell soils expand and heave or contract and crack during periods of high and low moisture content. The expansion and contraction cause the lifting and or sinking of structures, crack development, and eventual collapse of engineering structures. The need to stabilize such plastic soils to improve their load-carrying capacities cannot be overemphasized. Therefore in this article, the effect of lime contained in eggshells and its application in the stabilization of shrink-swell soils have been explored. 4wt% and 8wt% of eggshell powder were mixed with equal masses of two different soil samples from Dodowa (DD) and Adalekope (AD) in Ghana. The samples were characterized with X-ray fluorescence (XRF), Plasticity Index analysis (PI), Free Swell Index (FSI), pH test, and a grading test. The x-ray fluorescence results showed that eggshell contains about 52wt% of CaO, which is largely responsible for soil stabilization. The sample mixed with 8wt% eggshell powder showed a decreased PI, FSI, and a high silt/clay fraction. The results obtained have been discussed and can influence the application of eggshell powders for large-scale stabilization of expansive soils.