International Journal of Engineering Research in Africa Vol. 55

Abstract: Titanium (Ti) alloys are materials of interest in structural and chemical applications due to their low density, outstanding mechanical and chemical resistance properties. However, the mechanical properties still need to be enhanced to make them suitable as a replacement for Ni-based superalloys. There have been significant breakthroughs in the reinforcement of Ti alloy with a small weight percentage (wt.%) of ceramics. This work investigates the effect of TiN nanoparticles’ addition on the densification, phase transformation, microstructure, hardness, and compressive properties of Ti-7Al-1Mo ternary alloy. 3 wt.% of TiN nanoparticles was blended with Ti-7Al-1Mo powder, and the resulting admixed powder was consolidated via spark plasma sintering technique at 50 MPa pressure, 10 min holding time, and 1000 °C temperature. Scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry were used to characterise the microstructure and phase composition respectively. The microstructure of Ti-7Al-1Mo revealed a lamellar structure with alpha (α) phase and minor beta (β) phase with visible grain boundaries, while TiN reinforced Ti-7Al-1Mo composite microstructure shows a bimodal structure with reduction in the lamellar structure. Ti-7Al-1Mo ternary alloy has a hardness value of 352±17 HV0.1 and a compressive yield strength of 985±31 MPa. The composite shows an increment of 74 HV and 323 MPa in its hardness and compressive yield strength respectively in comparison to the ternary alloy.

Abstract: Global increase in fuel prices and the associated problem of harmful emissions from combustion of fossil fuels has necessitated the need for more energy sources to sustain energy security and mitigate the negative environmental implications from the continuous use of petroleum diesel. This research is primarily focused on the production of biodiesel from Melia azedarach oil, which has not been much explored as a feedstock for diesel substitute. In consideration of the nutritional demands for edible oil seeds, the use of edible vegetable stock to produce biodiesel raises major ethical concerns with non-edible oil seeds presenting more feasible solution to energy crises. Oil was extracted from Melia azedarach seeds by exploring both mechanical and chemical methods. Biodiesel was produced from the extracted oil via alkali alcoholysis. An innovative Ultraviolet-Visible Spectroscopy (UV-VIS) was adopted as a process tracking mechanism for biodiesel production. An oil yield of 4.32% of crude oil was extracted using n-hexane under an extraction time of 24h and temperature of 55°C. Esterification parameters of 45:1 Molar concentration of alcohol to oil, reaction temperature of 53°C, a reaction time of 50 mins and concentrated sulphuric acid weight fraction of 5% gave a free fatty acid conversion of 89.37%. Based on the results obtained, the seed oil has been established as a promising feedstock with promising efficiency for biodiesel production. However, large scale extraction of oil from the seed for industrial production of biodiesel must be further investigated.

Abstract: Wood sawdust, one the high volume agricultural wastes in Nigeria, occupies space and constitutes environmental nuisance. Burning, it produces green house gases. Converting it to adsorbents is economical and environmental benign. This work assessed the adsorptive capacities of two Danielliaoliveri sawdust-based adsorbents for the removal of ibuprofen from waste stream. The sawdust was carbonized and activated with ZnCl₂ and H₃PO₄ to produce adsorbents code-named ZCAC and PAAC respectively. The physicochemical properties of the adsorbents were determined and batch adsorption experiments performed. The optimum pH for the adsorption of ibuprofen onto the ZCAC and PAAC was 3. The isotherm studies revealed that the Ibuprofen (IBU)-ZCAC system data fitted Redlich-Peterson and Langmuir models. The data also fitted Pseudo-second order and Boyd kinetics, defined intraparticle diffusion of the adsorbate molecules. The process was physical and endothermic. For the adsorption onto PAAC, the data fitted the Freundlich and the Halsey models. The data also fitted the Pseudo-second order and the Elovich kinetics. The process was endothermic. The adsorption capacities of ZCAC and PAAC for IBU were 3.876 and 15.385 mg/g respectively. ZCAC and PAAC were promising adsorbents for remediation of wastewater contaminated with ibuprofen.

Abstract: The United Nations, through its Sustainable Development Goals, have identified access to clean water as one of the challenges facing society. With reported global deaths exceeding 1 million annually linked to untreated water consumption, which is usually contaminated by pathogenic micro-organisms, further research continues in water disinfection. The direct generation of non-thermal plasma in water is a promising method for the inactivation of disease-causing bacteria present in the wastewater. This study explored the efficacy of plasma in the inactivation of different bacterial densities (4.0×10⁴, 1.5×10⁵, and 2.5×10⁷ CFU/mL) using a 500 mL plasma batch reactor operating at atmospheric pressure. The plasma discharge was generated in water by a Technix-SR-10R-5000 high voltage direct current power supply in negative polarity with a set current of 0.45 A and a maximum pre-set ignition voltage of 9 kV. The electrodes used in the discharge was a copper material. A bacterial culture of Escherichia coli ATCC® 25922TM (E. coli) was used as a model for the direct plasma discharge. The study further investigated the contribution of copper ions (0.4 and 0.7 mg/L) released into the water during treatment by having two control reactors that were not exposed to plasma. The results show a complete inactivation at 180 seconds for the bacterial densities from 4.0×10⁴ to 2.5×10⁷ CFU/mL. The results from this study indicated the potential of a direct electric discharge in handling water source with high-bacteria densities.

Abstract: In this study, therefore, multi-walled carbon nanotubes (MWCNTs) were prepared on account of morphology, particle size and thermal properties of CNTs from high-density polyethylene (HDPE) waste and polypropylene (PP) using pyrolysis in the presence of Fe/Mn/Al catalyst. A comparison between the produced CNTs and commercially available CNTs was conducted to analyse if any deviations exist between both products. It was discovered that The commercial CNTs properties have similarities with the MWCNTs produced from plastic wastes. These materials were found to differ in purity with 1% error. The structures and morphologies of these materials are comparable as they were found to be crystalline and they revealed lattice fringes. They differ by the planes in the structural orientation. The MWCNTs synthesized from plastic wastes showed low thermal stability as opposed to the commercial CNTs.