https://ir.unisa.ac.za/handle/10500/30978 Wed, 06 May 2026 12:52:57 GMT 2026-05-06T12:52:57Z https://ir.unisa.ac.za/handle/10500/31513 A Study on Physicochemical Characteristics of Vetiver Grass (Vetiveria Zizanioides) in Bioenergy Production Sebola, Mmabyalwa R.; Maqhiza, Charmain T.; Sempunga, Baraka C.; Makgato, Seshibe S.; Bambo, Mokae F. The use of lignocellulose biomass is crucial in biofuel production, to enhance global energy security and avoid food shortages. Feedstock selection of this type of biomass depends on factors such as cellulose, hemicellulose, lignin content, sustainability, quantity, and availability. As such, a good understanding of chemical attributes is crucial for potential energy conversion. Before characterization, the grass was ground and sieved to 0.6 mm for uniformity. The Vetiver grass (VG) was then analyzed through proximate, ultimate, SEM, FTIR, and lignocellulosic characteristics analysis. The VG had 7.63 % moisture content, 4.46 % ash, 69.10 % volatile matter, and 18.81 % fixed carbon. The ultimate analysis showed that the C, H, O, N, and S content was 42.28 %, 5.54 %, 51.54 %, 0.64 %, and 0 %, respectively. Compared to Napier grass, cow dung, and sugar cane bagasse, VG had lower nitrogen and no sulfur with an empirical formula of CH1.6O0.92. The treated VG sample showed increased intensity in the FTIR peak at 1037 cm-1 and additional peaks at 2341 cm-1. Broadening of the peak at 3332 cm-1 indicated improved availability of cellulose and hemicellulose for methane production due to mechanical treatment. The SEM analysis showed the removal of the link between the hemicellulose, cellulose, and lignin cross-linking structure. These results suggest that VG could be a promising bioenergy source. Sat, 15 Jun 2024 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/31513 2024-06-15T00:00:00Z https://ir.unisa.ac.za/handle/10500/31512 Analysis of Municipal Solid Waste in Soweto, Johannesburg Municipality, South Africa: Implications for Sustainable Waste Management Practices Makgato, Seshibe The generation of municipal solid waste (MSW) has been consistently increasing due to various factors, such as the improvement of living standards, urban migration for employment opportunities, and, most notably, rapid population growth. In South Africa, inadequate collection and transportation methods result in the accumulation of solid waste. The objective of this study is to quantify and analyse the composition of municipal solid waste by type, evaluate proximate and ultimate analysis, and assess the potential effectiveness of energy generation from Johannesburg City in Soweto. According to the proximate analysis findings, the MSW contains a significant amount of moisture and ash. Therefore, it requires additional separation and purification processes before its utilization. The elemental analysis results indicate that the waste material has a decreased concentration of sulfur and nitrogen, which is desirable. The study's findings can help to select and design the thermal waste-to-energy (WTF) process for the composition of the studied waste, thereby expediting the transition to a circular economy in urban regions and reducing pollution. Sat, 15 Jun 2024 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/31512 2024-06-15T00:00:00Z https://ir.unisa.ac.za/handle/10500/31511 Charge Redistribution in Nise₂/Mos₂ n–n Heterojunction Towards the Photoelectrocatalytic Degradation of Ciprofloxacin Yusuf, Tunde L.; Olatunde, Olalekan C.; Masekela, Daniel; Modibane, Kwena D.; Onwudiwe, Damian C.; Makgato, Seshibe This study reports the photoelectrocatalytic (PEC) activity of a n–n heterojunction comprising MoS2 and NiSe2. The synthesis of the composite was achieved through a facile solvothermal method, yielding an exfoliated MoS2 layered sheet loaded with NiSe2 nanoparticles. Under visible light radiation and an external electric field, the obtained composite NiSe2/MoS2 exhibited enhanced catalytic activity for ciprofloxacin (CIP) degradation. The NiSe2/MoS2 heterojunction achieved about 78% degradation efficiency with a first-order kinetic rate of 0.0111 min-1, compared to 38% efficiency and a first-order kinetic rate of 0.0044 min-1, observed for MoS2. The NiSe2/MoS2 heterojunction was more advantageous due to the synergy of charge carrier induction by visible light radiation and improved charge carrier separation induced by the external electric field. The formation of n–n heterojunction at the interface of the two materials resulted in charge redistribution in the materials, with a simultaneous realignment of the band structure to achieve Fermi energy equilibration. The primary reactive species responsible for CIP degradation was identified as the photo-induced h+. Furthermore, the catalyst exhibited high stability and reusability, with no significant reduction in activity observed after five experimental cycles. This study reveals the potential of exploring the synergy between the photocatalytic and electrocatalytic processes in removing harmful pharmaceutical compounds from water. Thu, 25 Jul 2024 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/31511 2024-07-25T00:00:00Z https://ir.unisa.ac.za/handle/10500/31217 Monoclinic α-Bi2O3 nanorods by microwave-assisted synthesis: Photocatalytic and antioxidant properties Mohamed, Marwa; Ferjani, Hela; Oyewo, Opeyemi; Ogunjinmi, Oluwasayo; Hamed, Seham; Amairia, Chahra; Makgato, Seshibe; Onwudiwe, Damian Nanotechnology has emerged as a new route for addressing most environmental and medical challenges, hence this field of research continues to generate research interest. Herein, Bi₂O₃ was synthesized by a microwave- assisted thermal process. X-ray diffraction (XRD) result confirmed that a nanocrystalline monoclinic crystal structure of the α-phase was formed, and both the Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis confirmed that the synthesized α-Bi₂O₃ were rod-like in shape. The length of the nanorods was in the range of 60–160 nm, with an average dimension of 101.5 nm, while the width has an average value of 23 nm. A band gap energy value of 2.75 eV was obtained from the absorption spectroscopy, and they absorbed light in the UV to visible range, with an absorption maximum of around 345 nm. Photocatalytic activity of the nanorods under UV irradiation was investigated by assessing the degradation of Bromocresol green (BG) as a model pollutant. The degradation process of the dye molecules was studied at different concentrations (20–80 mg/L), varied photocatalyst dosage (0.025, 0.05, 0.075, and 1.0 g), and a range of solution pH (3, 6, 9, and 12). About 75 % optimum photocatalytic efficiency was achieved at pH 6 after 3 h. In addition, the results showed that an increase in catalyst dosage and concentration of dye molecules contributed to promoting the degradation effect. Moreover, the photocatalyst was found to be stable after 4 consecutive cycles, with negligible loss of efficiency. The antioxidant potency of the nanorods was assessed by evaluating their free radical scavenging capabilities across 4 different assays: 1,1-diphenyl-2-picrylhydrazyle (DPPH), Nitric oxide (NO), Hydrogen peroxide (HP) radical inhibition, and Reducing power (RP). The results from the IC₅₀ values indicated the sample exhibited better inhibition of HP (25.22 µg/mL), followed by RP (28.22 µg/mL), NO (29.37 µg/mL), and DPPH (32.72 µg/mL) respectively. However, the standard Ascorbic acid exhibited IC₅₀ values of 16.25,.07, and 28.40 µg/mL for DPPH, RP, HP, and NO, respectively. These unique properties of the nanorods owed that they have good antioxidant potential that is comparable with that of Ascorbic acid used as the standard. Fri, 17 May 2024 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/31217 2024-05-17T00:00:00Z