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.