Applied Chemistry Publications
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- ItemApplication of polymer‑coated Macadamia integrifolia nutshell biomass impregnated with palladium for chromium(VI) remediation(Scientific Reports, 2021) Moyo, M.; Modise, S. J.; Pakade, V. E.Freely suspended and porous basket restrained granules of palladium nanoparticles supported on polymer-grafted Macadamia nutshell biomass (Pd@Polym-MNS) composite were used for the treatment chromium(VI)-containing water. In the presence of formic acid, the Pd@Polym-MNS demonstrated its activity in the adsorption-reduction-based conversion of noxious chromium(VI) to less toxic chromium(III) with a low activation energy of 13.4 kJ mol–1, ΔH0 (+ 10.8 kJ mol–1), ΔS0 (−270.0 J mol–1 K–1), and ΔG0 (+ 91.3 to + 98.0 kJ mol–1) indicated the exothermic, endergonic and non-spontaneous nature of the catalytic redox reaction. In addition to facilitating easy recovery, rinsing, and reuse, restraining the Pd@Polym-MNS in the basket reactor helped maintain the integrity of the catalysts by preventing violent collisions of suspended granules with the mixing apparatus and the walls of the reaction vessel. Whereas the pseudo-first-order rate constant was recorded as 0.157 min–1 upon initial use, values of the mean and relative standard deviation for the second, third and fourth consecutive uses were found to be 0.219 min–1 and 1.3%, respectively. According to a response surface methodological approach to batch experimentation, the initial concentration of chromium(VI) and catalyst dosage had the greatest impact on the redox reaction rate, accounting for 85.7% and 11.6% of the variability in the value of the pseudo-first-order rate constant, respectively. Mutually beneficial effects of the combinations of high formic acid and low chromium(VI) concentration, high temperature and catalyst dosage as well as high formic acid and catalyst dosage were recorded.
- ItemMajor challenges for commercialization of perovskite solar cells: A critical review(ELSEVIER, 2025-01-09) Seyisi, T.; Fouda-Mbanga, B.G.; Mnyango, J.I.; Nthwane, Y. B.; Nyoni, B.; Mhlanga, S.; Hlangothi, S. P.; Tywabi-Ngeva, Z.Global electricity consumption increases rapidly creating strain on the grid. In contrast, the primary sources of electricity are fossil fuels such as gas, coal, and oil which are non-renewable and limited, resulting in energy crises. Therefore, the global energy crisis remains a big challenge that requires renewable and sustainable solutions. Perovskite solar cell is a type of solar cell that uses a perovskite-structured compound, usually a hybrid organic-inorganic lead or tin halide-based material as the light-harvesting active layer. In the development of perovskite solar cells spanning 2009–2024, exceptional power conversion efficiencies ranging from 3.8 % to 26.1 % have been reported. As such, perovskite solar cells hold significant promise as the next generation of affordable and effective photovoltaic solar cell technology. Moreover, perovskite solar cells have recently gained popularity and presented an excellent commercial opportunity because they are made from readily available and inexpensive raw materials. However, the commercial production and utilization of perovskite solar cells remains immature. It has been shown that perovskite solar cells containing titanium dioxide as the electron transport layer exhibit poor stability, degrading quickly under prolonged exposure to sunlight and humid conditions. These instability concerns are the major drawbacks that threaten efforts that are directed at the commercialization of perovskite solar cells. As such, there are significant efforts to improve the development of scalable fabrication of perovskite solar cells and the establishment of industrial production lines. The main objective of this review is to outline the primary obstacles that hinder the commercialization of perovskite solar cells. Firstly, a brief discussion on the principles of perovskite solar cells is done. Secondly, challenges associated with the commercialization of erovskite solar cells and counterstrategies are discussed. The review concludes by looking at perspectives and prospects highlighting the importance of continued research and collaboration in overcoming challenges to commercialization. We hope that this review will provide useful insights for future research on improving the stability of cutting-edge perovskite devices as they approach commercialization.
- ItemBiofuel Policy as a Key Driver for Sustainable Development in the Biofuel Sector: The Missing Ingredient in Zimbabwe’s Biofuel Pursuit(Canadian Center of Science and Education, 2013-12-14) Moyo, P.; Moyo, M.; Dube, D.; Rusinga, O.As global warming continues to be a challenge, there is urgency to look into fossil fuel alternatives for sustainable energy supplies which have also been hastened by the volatility of crude oil prices and the fact that fossil fuel depletion is clearly in sight. Zimbabwe has not been spared of the negative effects of climate change which have affected both the food and energy sectors. This has proved to be a major challenge for the sustainable development of the country’s economy. In an effort to be energy independent, the country has for over decades looked into the prospect of utilising its vast biomass resources to produce biofuels. These programmes have been met with a number of challenges which has seen most such projects not succeeding. The current paper gives a narration of the history of biofuel programmes in Zimbabwe looking at their driving factors and reasons that led to their collapses. Lack of a national biofuel policy is identified as the major factor that has been the missing link in the past and must be addressed. The paper goes further to call for the crafting of a National Biofuel Policy for Zimbabwe highlighting the major thematic issues it would need to cover. An implementation plan for the programme has been proposed
- ItemAdsorption of Lead and Copper by Carbon Black and Sodium Bentonite Composite Material.(Chemic Publishing Company, 2017-10-30) Chiririwa, H.; Matthews, T.; Nyoni, B; Majoni, Stephen; Naidoo, E.BThe efficiency of using a composite of carbon black and sodium bentonite in treating drinking water contaminated with lead and copper ions was analyzed. The effects of pH, contact time, concentration and adsorbent dosage using an adsorbent composite of 20 % sodium bentonite and 80 % carbon black were studied. The adsorption data was analyzed with respect to Langmuir, Freundlich and Temkin isotherms. The data fits well with the Langmuir isotherm model with high coefficients of determination for both metal ions adsorption. The adsorption kinetics follows a pseudo second-order model for both metal ions. The maximum metal ion uptake (qmax) of composite adsorbent is 7.69 and 0.80 mg/g for lead and copper, respectively.
- ItemThermal degradation kinetic study of polystyrene/organophosphate composite(Elsevier, 2018) Majoni, Stephen; Chaparadza, AllenA polystyrene/bis (2, 4-dicumylphenyl) pentaerythritol diphosphate (DPP) composite (PS-DPP) with a DPP loading of 10% (w/w) was prepared by the melt-compounding method. Results indicated that DPP had a thermal destabilization effect at temperatures below 380 °C. A comparative degradation kinetic analysis was performed employing the Kissinger method and the isoconversional methods of Friedman, Starink and Advanced Isoconversional Method (AICM). Variation of activation energy with extent of conversion (α) results from all the isoconversional methods showed that activation energy did not vary significantly with α for both pure PS and PS-DPP. Activation energies obtained from the Starink method above 380 °C were very close to those obtained from AICM consistent with activation energy values not varying significantly with α. The y(α) master plots and the Friedman methods where used to identify the reaction model and calculate the frequency factor respectively. The Sestak-Berggren model was identified as the most appropriate model to describe the thermal degradation of both PS and PS-DPP. The overall results indicates that activation energies of the composite were not significantly higher than those of pure PS at low conversion (α < 0.2) where DPP had a destabilizing effect but became higher when DPP had a stabilization effect.