College of Basic and Applied Sciences
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Item The effect of NaOH catalyst concentration and extraction time on the yield and properties of Citrullus vulgaris seed oil as a potential biodiesel feed stock(South African Journal of Chemical Engineering, 2018) Efavi, J.K.; Kanbogtah, D.; Apalangya, V.; et al.In this work, oil was extracted from Citrullus vulgaris (watermelon) seeds for potential feedstock in biodiesel production. The results showed that the oil content from Citrullus vulgaris seeds oil during extraction reached an average yield of 50%. Biodiesel was produced via transesterification using NaOH as a catalyst. The effect of NaOH on the yield of the biodiesel was investigated at three different traditions; 0.13, 0.15, and 0.18 g, and oil to methanol ratio of 5:1 under different reaction times; 90, 120 and 150 min at 60 C. The yield of biodiesel from NaOH concentration of 0.13 g was found to be 70% compared to those of concentrations of 0.15 g and 0.18 g which were 53% and 49% respectively. Gas chromatography was used to identify the methyl ester groups present in the biodiesel and the results revealed both concentration and time-dependent increase in oil yield. The physicochemical properties of the watermelon seed oil such as flash point (141.3 ± 0.4e143.4 ± 0.2), density (0.86 ± 0.04 e0.91 ± 0.01 g/cm3 ), kinematic viscosity (30.50 ± 0.1e31.20 ± 0.04 mm2 /s) and acid value (mg KOH/g) are similar to conventional vegetable oils. This work, therefore, highlights the potential utility of watermelon seeds for biodiesel production.Item Surface Functionalized MXenes for Wastewater Treatment-A Comprehensive Review(Global Challenges, 2022) Damptey, L.; Dodoo-Arhin, D.; Jaato, B.N.; et al.Over 80% of wastewater worldwide is released into the environment without proper treatment. Whilst environmental pollution continues to intensify due to the increase in the number of polluting industries, conventional techniques employed to clean the environment are poorly effective and expensive. MXenes are a new class of 2D materials that have received a lot of attention for an extensive range of applications due to their tuneable interlayer spacing and tailorable surface chemistry. Several MXene-based nanomaterials with remarkable properties have been proposed, synthesized, and used in environmental remediation applications. This work, a comprehensive review of the state-of-the-art research progress on the promising potential of surface-functionalized MXenes as photocatalysts, adsorbents, and membranes for wastewater treatment are presented. The sources, composition, and effects of wastewater on human health and the environment are displayed. Furthermore, the synthesis, surface functionalization, and characterization techniques of merit used in the study of MXenes are discussed, detailing the effects of a range of factors (e.g., PH, temperature, precursor, etc.) on the synthesis, surface functionalization, and performance of the resulting MXenes. Finally, the limits of MXenes and MXene-based materials as well as their potential future research directions, especially for wastewater treatment applications are highlighted.Item High energy milling of Cu2O powders(2011) Dodoo-Arhin, D.; Vettori, G.; D’Incau, M.; et al.Whole Powder Pattern Modelling was employed to investigate the microstructure changes in Cu2O powders milled in a vibrating cup mill. The reduction in the average size of coherently scattering domains - and simultaneous narrowing of the size distribution - occurs in the first minutes. An asymptotic limit of ca. 10 nm is obtained. The size reduction is obtained at the expense of introducing a massive quantity of dislocations in the system, reaching a limit of ca. 4×10-16 m-2. A proper nanocrystalline microstructure can be obtained with an effective milling time of ca. 20 min.Item 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.Item High-performance symmetric electrochemical capacitor based on graphene foam and nanostructured manganese oxide(AIP Advances, 2013) Bello, A.; Dodoo-Arhin, D.; Gogotsi, Y.; et al.We have fabricated a symmetric electrochemical capacitor with high energy and power densities based on a composite of graphene foam (GF) with ∼80 wt% of manganese oxide (MnO2) deposited by hydrothermal synthesis. Raman spectroscopy and X-ray diffraction measurements showed the presence of nanocrystalline MnO2 on the GF while scanning and transmission electron microscopies showed needle-like manganese oxide coated and anchored onto the surface of graphene. Electrochemical measurements of the composite electrode gave a specific capacitance of 240 Fg−1 at a current density of 0.1 Ag−1 for symmetric supercapacitors using a two-electrode configuration. A maximum energy density of 8.3 Whkg−1 was obtained, with a power density of 20 kWkg−1 and no capacitance loss after 1000 cycles. GF is excellent support for pseudo-capacitive oxide materials such as MnO2, and the composite electrode provided a high energy density due to a combination of double-layer and redox capacitance mechanisms.Item Chemical adsorption of NiO nanostructures on nickel foam-graphene for supercapacitor applications(Journal of Materials Science, 2013) Bello, A.; Dodoo-Ahrin, D.; Makgopa, K.; et al.Few-layer graphene was synthesized on a nickel foam template by chemical vapor deposition (CVD). The resulting three-dimensional (3D) graphene was loaded with nickel oxide nanostructures using the successive ionic layer adsorption and reaction (SILAR) technique. The composites were characterized and investigated as electrode material for supercapacitors. Raman spectroscopy measurements on the sample revealed that the 3D graphene consisted of mostly few layers, while X-ray diffractometry (XRD) and scanning electron microscopy (SEM) revealed the presence of nickel oxide. The electrochemical properties were investigated using cyclic voltammetry, electrochemical impedance spectroscopy, and potentiostatic charge-discharge in aqueous KOH electrolyte. The novelty of this work is the use of the 3D porous cell structure of the nickel foam which allows for the growth of highly conductive graphene and subsequently provides support for uniform adsorption of the NiO onto the graphene. The NF-G/NiO electrode material showed excellent properties as a pseudocapacitive device with a high specific capacitance value of 783 Fg-1 at a scan rate of 2 mVs-1. The device also exhibited excellent cycle stability, with 84% retention of the initial capacitance after 1,000 cycles. The results demonstrate that composites made using 3D graphene are versatile and show considerable promise as electrode materials for supercapacitor applications.Item Surfactant Assisted Synthesis of Copper Oxide (CuO) Leaf-like Nanostructures for Electrochemical Applications(American Journal of Materials Science, 2014) Bello, A.; Dodoo-Arhin, D.; Makgopa, K.; et al.Three different copper oxide (CuO) leaf-like nanostructures have been synthesized by micelles microemulsion method using a surfactant of copper dodecyl sulfate (Cu(DS)2) by varying the concentration of sodium hydroxide (NaOH). This study was carried out to investigate the effect of NaOH concentration on the stability, crystalline domain, and pseudocapacitance behavior of the leaf-like nanostructures. The samples were characterized by X-ray diffraction (XRD), thermogravimetry analysis (TGA), Raman spectroscopy, Fourier-Transform Infrared (FTIR), scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). It was observed that the crystalline domain size (12 nm-18 nm) and size distribution of the as-synthesized nanocrystals decreased with increasing concentration of NaOH. The interaction mechanism and formation of the leaf-like structure have been elucidated and correlated with various analytical techniques. The domain size and NaOH concentration tend to influence the charge transfer resistance.Item Consumer Preference Heterogeneity and Preference Segmentation: The Case of Ecolabeled Salmon in Danish Retail Sales(Marine Resource Economics, 2020) Ankamah-Yeboah, I.; Asche, F.; Bronnmann, J.; et al.The popularity of sustainably produced food products has grown rapidly in recent years. Ecolabels are used to indicate the environmental sustainability of products and have been implemented in the seafood market, with the leading ecolabel being that of the Marine Stewardship Council (MSC) for wild fish. However, the effect of ecolabels on consumer decision-making remains unclear regarding actual purchasing behavior. This study analyzes scanner data from a household panel in Denmark, accounting for consumer heterogeneity using random parameters and latent class logit models to identify the effect of ecolabels. The results indicate substantial consumer preference heterogeneity concerning important salmon attributes. Salmon attributes that confer convenience to household fish consumption appear to be very important in consumer choices. Ecolabeling has a significant effect on household decision-making, but the majority of consumers are more likely to choose non-labeled products, which may be due to the low availability of eco-labeled products. Five consumer segments are identified, revealing one consumer segment with a preference for organic labeled salmon, comprising 15% of households. However, a consumer segment for MSC-labeled salmon is not identified. The implication is that management can rely on a segment of consumers to implement organic principles in salmon farming, but the preference for sustainable salmon fishing is inconclusive due to uncertain confounding effects.Item Physicochemical, Functional Properties And Mycotoxin Occurrence Of Ghanaian Tigernuts (Cyperus Esculentus L.)(University of Ghana, 2022-06) Battuta-DawlahIn Ghana, tigernut (Cyperus esculentus L.) is grossly underutilized in food applications and is mostly consumed raw as a snack. However, the soil and climate conditions of the country are conducive for cultivation of the crop on a large scale for applications in food for local consumption, industrialisation and for the export market. Food applications of tigernut and its derivatives and their possible inclusion as ingredient in the Ghanaian diet would require knowledge on its handling quality and functional properties. The aim of this study was to characterise Ghanaian tigernut as an ingredient for possible food applications. The study design consisted of two parts: (a) a cross-sectional survey of different categories of stakeholders using pre-tested semi-structured questionnaires (b) followed by laboratory designed experiments to study the quality, physicochemical and functional properties of tigernut as a function of tigernut variety and process conditions. For the surveys, a total of 1277 stakeholders in the value chain, comprising of 711 consumers and 487 traders (wholesalers/retailers) in Greater Accra region and 79 tigernut farmers in the Western and Eastern regions of Ghana, were interviewed using semi-structured researcher-administered questionnaires. The questionnaires sought to gain information on respondents’ level of knowledge on mycotoxins, as well as ascertain if measures were in place to mitigate the risk of fungal colonisation of the crop along the supply chain. Additionally, tigernuts collected at various points along the supply chain (farm, wholesale and retail) were analysed for their mycotoxin (aflatoxins and ochratoxin A) levels using reverse phase High-Performance Liquid Chromatography (HPLC), to determine the hot spots of mycotoxin contamination along the value chain. The second part of the study investigated the physical characteristics of tigernut tubers as well as the functional properties of tigernut flour with the aim of determining its suitability in food applications. Additionally, the shelf life of the tigernut flour was determined by accelerated shelf life testing using the Arrhenius model. Fresh tigernut milk is usually University of Ghana http://ugspace.ug.edu.gh iii characterised by the sedimentation of starch which influences its flow behaviour as well as the physical stability. Furthermore, heat treatment of the milk leads to gelatinisation of the starches, which also affects the same properties. Consequently, the effects of heat (by roasting tigernuts) and adding α- amylase to the tigernut milk on the physicochemical and functional properties of tiger nut milk were studied. Tigernut oil was extracted and the phenolic and functional properties were determined as well as the effect of heat on these properties. The macro nutritional composition of tigernut tuber, flour, oil and milk were also investigated. The results of the surveys showed that tigernut farmers and consumers had appreciable knowledge in and displayed better attitude towards the prevention of mycotoxin contamination than the tigernut traders (wholesalers/retailers). The educational level of all stakeholders influenced their attitude and knowledge towards the prevention of mycotoxin contamination. Almost all consumers were willing to try new tigernut products such as the flour, oil and milk and would like to see more of these products on the Ghanaian market. The number of samples and the levels of mycotoxins (Ochratoxin A and aflatoxins) increased as the value chain progressed, with retail samples containing all the mycotoxins analysed. Total mycotoxins ranged from 0-27 µg/kg at the farm stage to 0-52 µg/kg at the wholesale stage and finally to 7.9 to 1115.48 µg/kg at the retail stage. These highlight post-harvest stage of the value chain as the focal point for mycotoxin prevention programs, although mycotoxin prevention can be agreed as a cumulative process. Both black and yellowish-brown tigernut flours contained relatively high and comparable amounts of sucrose, glucose and fructose. The relatively high resistant starch content of the tigernut flour makes the flour ideal for diabetics and weight watchers. The yellowish-brown variety had higher total starch content, higher water-retaining ability and viscosity at heating and holding cycles as compared to the black variety. Titratable acidity was found to be the crucial determinant of spoilage in tigernut flour and higher temperature was observed to increase the oxidation of the tigernut flour. This may imply that tigernut flour should be stored below room temperature. Heat and the addition of α- amylase increased the total solids, brix and titratable acidity but caused a decrease in the pH of the tigernut milk. Addition of 0.2% of α- amylase to roasted tigernut milk improved its emulsion stability. Heat and addition of α- amylase caused the tigernut milk to become darker in colour. The flow behaviour of the tigernut milk exhibited shear thinning (pseudoplastic) fluid properties. This implies that commercial production of milk from tigernut must control parameters such as speed of machines during processing as well as concentrations of food additives such as α-amylase. Chemical qualities such as iodine value, peroxide value, ester value, saponification value, free fatty acids and acid value of oil extracted from tigernut tubers, all increased at higher temperatures whilst antioxidant activity and phenolic content decreased. The functional properties of tigernut oil suggested that the oil is good for frying at lower temperatures and for shorter periods. The carbohydrate component of the tigernut tuber was mainly made up of starch and dietary fibre (resistant starches) which reduced in the milk and oil. Crude fat was the second most abundant component in the tigernut tuber. Quercetin and gallic acid were found in appreciable amounts in the tigernut oil. Although, the protein content in the tigernut milk was lower compared to the tuber, it was probably enough to impart desirable functionality to help stabilize the tigernut milk. Tigernut tuber and its derivatives can offer various options in food products. The safety of the tuber and its products can however be improved when stakeholders of the supply chain are educated and supported to implement strategies that prevent mycotoxin contamination.Item Assessment of Agricultural Advisory Messages from Farmer-to Farmer in Making a Case for Scaling Up Production: A Qualitative Study(The Qualitative Report, 2020) Kwapong, N.A.; Ankrah, D.A.; Boateng-Gyambiby, D.; et.alInadequate access to agricultural extension services often results in poor farm practices, affecting yields and subsequently the income and well-being of smallholder farmers. Given the high demand for agricultural information and the limited capacity of extension services, a farmer-to-farmer extension approach has been explored by many underserved farmers. In this study, we use a qualitative case study approach to explore how cassava farmers who had limited access to agricultural advisory services from public extension agents managed to up-scale their farming business. Our research question was: what lessons can be learned from the lived experience of these farmers to address the current challenges of cassava farming? The results of our study revealed diversity in advisory messages from farmer to farmer and agricultural extension agents. Farmers’ messages focused on encouraging farmers’ commitment and motivation towards farming business, availability of needed financial resources for the entire production season, willingness to reinvest profits, and access to farmland for future expansion. In contrast, the traditional messages from agricultural extension agents focused on encouraging group formation to address marketing challenges, diversification of farm operations, and good agricultural practices. These results show the need for pluralistic extension approaches to ensure farmers get access to necessary information. Keywords: Agricultural Extension, Case Study, Farmer to Farmer Extension, Social Learning