Applied Chemistry

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Applied Chemistry

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The effect of air sparging on the electrical resolution of water-in-oil emulsions
(Elsevier Science Ltd., 2001) Bailes, P.J.; Kuipa, Pardon K.
A novel process is described in which the resolution of a stable water-in-oil emulsion is augmented by the simultaneous use of pulsed DC electric 1elds and mild bubbling of the emulsion with air. The work has indicated that there is a synergistic effect of air sparging on demulsi1cation in the electric 1eld and that the maximum emulsion resolution requires the voltage to be pulsed with optimum frequency. Emulsion resolution was found to increase steadily with increasing air 5ow rate until a maximum value is reached after which the extent of phase separation starts to fall rapidly with further increase in the air 5ow rate. The electrical resolution was best (79% resolution) when the ratio of air to emulsion 5ow rate (volumetric) in the coalescer was about 120 : 1.
An assessment of the quality of liquid effluents from opaque beer-brewing plants in Bulawayo, Zimbabwe
(2005-07) Kuipa, Pardon K.
The quality of liquid effluents from two opaque sorghum beer-brewing plants in Bulawayo, Zimbabwe were studied by analysing snap and composite samples collected manually from the plants’ effluent discharge points over a period of six months. Both plants generate effluents that could negatively impact on the municipal treatment system if no efforts are made to significantly reduce their pollution load in terms of both quality and quantity. The results from both plants for the main pollution indicators showed high values of chemical oxygen demand (COD) (in excess of 30 000 mg/l in some instances), biological oxygen demand (BOD) and suspended solids (SS), indicating high organic load. Analysis of BOD values indicates that the effluents are biologically degradable. No significant heavy metals were found in the effluents, as these are food-processing plants. The effluent treatment plants in both plants were not only inadequate but also poorly operated thereby rendering them ineffective in reducing the pollution loads of the effluents. Simple good housekeeping and operational practices and well as design modifications are suggested to reduce the pollution load of the effluents.
Analysis of acrylamide in traditional foodstuffs in Zimbabwe
(Academic Journals, 2011) Sanganyado, Edmond; Parekh, Champaklal T.; Eriksson, S.
We carried out a preliminary study on the occurrence of acrylamide in potentially high risk traditional foodstuffs consumed in Zimbabwe. Various studies have shown that acrylamide, a ‘probable human carcinogen’, is formed by high temperature thermal processing of carbohydrate rich foodstuffs (lnternational Agency for Research on Cancer, 1994). Acrylamide concentrations in roasted maize, groundnuts, soy beans and boiled maize were determined using liquid chromatography tandem mass spectrometer (LC-MS/MS). The relative standard deviation of the analytical technique was 5% and the limit of detection was 0.02 μg/kg. Acrylamide was not detected in boiled maize. Roasted maize contained 450 μg/kg acrylamide. Roasted groundnuts had 140 μg/kg and finally, roasted soybeans with a concentration of 70 μg/kg acrylamide.
New routes to the preparation of [ru3(co)12], [h4ru4(co)12], [rucl2(pph3)3] and [rucl2(cod)]n from anglo platinum refinery
(Zimbabwe Journal of Science and Technology, 2013) Chiririwa, Haleden; Moss, John R.
New and improved routes for the preparation of ruthenium complexes are described. [Ru3(CO)12], [H4Ru4(CO)12], [RuCl2(PPh3)3] and [RuCl2(COD)]n have been prepared from [(NH4)2RuCl6] and [H2RuCl6]. Traditionally these ruthenium complexes have been prepared from commercially available RuCl3.3H2O, but here we describe their preparation from refinery materials.
Occurrence of pesticides used in tobacco farming in edible vegetables and environmental samples
(2013-09) Munjanja, Basil K.; Madzivire-Penduka, Cecilia; Sanganyado, Edmond
A method was developed and validated for the analysis of chlorothalonil (CT), dimethoate (DM) and triadimenol (TD) in soil, surface water and edible green vegetables. In method development, A range of solvents were evaluated, and ethyl acetate was observed to be the best extracting solvent in soil and vegetable samples, while acetonitrile was the best extracting solvent in water samples. The effect of solvent type, solvent volume and extraction time on recovery of pesticides was studied. Analysis was carried on HPLC-UV a C18 column using a mobile phase comprising CH3CN/water (50:50, v/v) with a flow rate of 1.0ml/min in isocratic mode. The pesticides were extracted by ultrasonication and obtained recoveries in water, soil and vegetables ranged from 65-91 %. Furthermore, the detection limit in water, soil and vegetables was 0.01 µg/L, 2.8 µg/kg and 0.005 µg/kg, respectively. Limits of quantification ranged from 0.25-1.25µg/kg for vegetables, 1.35-2.3µg/kg and 0.02-0.05µg/l. Precision was measured in terms of the RSD, and values were less than 10%. The method was successfully applied to the analysis of incurred vegetable, soil and water samples from 3 farms from Bromley A2 agricultural area near Marondera, Zimbabwe. About 1.6µg/kg of CT was detected at one farm in soil samples, DM (0.025µg/l) was detected at another farm in well water. However, TD was not detected in all samples and no pesticides were detected in vegetable samples.
Biofuel 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
Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure
(Hindawi Publishing Corporation, 2014-01-16) Majoni, Stephen; Hossenlopp, Jeanne M.
Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs) and hydroxy double salts (HDSs) can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release.The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers.The orthoisomer showed a more sustained and complete release as compared to the other isomers.
Recovery of Lead from Lead Laden Cupels by a Simultaneous Leaching and Electrowinning Process in a Methanesulphonic acid bath
(Sphinx Knowledge House, 2014-07) Mangunda, Cledwyn T.; Kuipa, Olga; Sithole, Tapuwa R.; Kuipa, Pardon K.
Cupels are generated by mines during the fire assaying of precious group metals. The cupels contain lead which is a known environmental hazard hence the need to recover it. This work illustrates how leaching and electrowinning processes can be combined to produce a hybrid lead recovery process. Bench scale tests were conducted for the hybrid leaching and electro winning process using Methane Sulfonic Acid (MSA) as a leaching solvent at a concentration of 200g MSA per litre of water. A glass electrowinning cell fitted with a 9cm × 4cm pure lead cathode and 9cm × 4cm graphite anode with inter electrode gap of 15cm and a magnetic stirrer bar was used. Lead laden cupels (containing 30g lead) were subjected to simultaneous leaching and electrowinning and lead recovery after a period of 80 minutes was found to be 98%. The hybrid process was found to require about 20% less solvent than that required for the convectional leaching process which requires multiple stages to reduce the concentration of the solute in the raffinate to the same extent.
Trends in the control of NOx and SOx combustion emissions: Implications to the design of fluidised bed combustion operations.
(Chinese Journal of Mechanical Engineering, 2015-07) Kuipa, Pardon K.
This paper attempts to review the implications of the sulphur oxides (SOx), nitrogen oxides (NOx) and nitrous oxide (N2O) emissions to the design of fluidised bed combustion (FBC) operations. The review focuses on how the knowledge of SOx and NOx emissions trends can be applied to influence the design of FBC operations. The effects of the emission trends of these noxious gases on the design operations for FBC such as temperature control, nozzle designs, sorbent selection design, air supply and control designs were reviewed. The implications of SOx, N2O and NOx emissions on the design of FBC systems rest primarily on the need to design the operational conditions of the system. The design for the precise location of the fuel feeding ports, secondary air feeding ports, limestone feeding ports and a prescribed size and quantity of sorbents to feed into the system was found to be crucial for reduction of these emissions. The emissions also have an impact on the design of the distributor plate of the system; reduction of the emissions necessitates good fluidisation and well-regulated temperature within the system. The review therefore concludes that there is a close nexus between the design and operation of FBC systems with NOx, N2O and SOx emissions.
Characterization of acid tar waste from benzol purification.
(Journal of Chinhoyi University of Technology, 2015-07) Kuipa, Pardon K.
Determination of the Most Effective Concentration of Deet and Permethrin in A Mosquito Repellent Soap and Assay of the Active Ingredients
(Research India Publications, 2016) Mtisi, Farlane; Parekh, Champaklal T.; Ochieng, Aoyi; Chiririwa, Haleden
The study was carried out to investigate the most effective concentration of DEET and Permethrin in a mosquito repellent soap and to develop a method for the assaying of the active ingredients. The effect of perfume in a repellent soap was also investigated. In the study nine soaps were prepared and the concentrations of DEET and Permethrin were varied with six soaps having both ingredients. Efficacy tests were carried out on the different soaps. The most effective and economic soap in repelling mosquitoes was the one which had 50 % DEET. Physical and chemical tests revealed that the soaps had an average total fatty matter of 71.6 %, average moisture content of 14.35 % and average free alkali of 0.04.
Re-Visting the Electricity-Growth Nexus in South Africa
(De Gruyter, 2016) Phiri, Andrew; Nyoni, Bothwell
This research study contributes to the ever-expanding literature by examining multivariate cointegration and causality relationships between electricity consumption, economic growth and other growth determinants for quarterly South African data collected between 1994/Q1 – 2014/Q4. The motivation behind this current research case study becomes apparent when taking into consideration that no previous studies have gone further than bivariate and trivariate analysis in investigating the electricity-growth nexus in South Africa. In conducting our empirical investigation, our obtained empirical results are two-fold in nature. Firstly, we find significant multivariate long-run cointegration relationships between economic growth, electricity consumption and other growth determinants. Secondly, our empirical analysis offers support in favour of the neutrality hypothesis, that is, the notion of no causal effects existing between electricity consumption and economic growth in the long-run. However, we find that exports directly cause electricity consumption whereas economic growth, domestic investment and employment levels causally flow to exports.
Removal of Chromium and Nickel from Electroplating Wastewater using Magnetite Particulate Adsorbent: (1) Effect of pH, Contact Time and Dosage, (2) Adsorption Isotherms and Kinetics
(Canadian Center of Science and Education, 2016-02-06) Dube, Donatus; Champaklal, Parekh T.; Nyoni, Bothwell
Wastewater discharged into municipal sewer systems from electroplating process plants contains a heavy load of metal ions and often requires pre-discharge treatment. Treatment of wastewater to reduce the concentration of metal ions employing an adsorption process has been studied using a wide range of adsorbents. In this work, the concentrations of chromium and nickel ions in wastewater samples from a local electroplating shop were found to be above the limits set out by the Bulawayo City Council, and the Environmental Management Agency, a statutory agency under the Ministry of Environment and Tourism, Government of Zimbabwe. Furthermore, the removal of chromium and nickel ions from the wastewater using magnetite as an adsorbent is studied. Magnetite particulate adsorbent used in this experiment has demonstrated to be an effective adsorbent material. At the optimum process operating pH of 4 – 7 the absorbent was able to achieve removal rates of up to 99% for chromium and 98% for nickel. The adsorption processes for chromium and nickel have been proven to be physical in nature using the Dubinin-Radushkevich isotherm model. Also, the adsorption kinetics data fit well with pseudo second-order kinetic model.
Adsorption 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.B
The 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.
Effectiveness of Biopolymer-Bentonite Clay Composites in Wastewater Treatment
(2018) Mupasi, N.M; Dube, Donatus; Chiririwa, H; Naidoo, E.B
The feasibility of employing wood-bentonite clay composite material as a low-cost and effective adsorbent for removal of cations from wastewater has been investigated. The wood-bentonite clay composites were prepared by a solution intercalation method. Results showed that the percentage adsorption of Pb 2+ , Mg 2+ and Ca 2+ from the effluent water was 88.46, 81.12 and 95.76 % respectively, using 10 g/L of the adsorbent. The desorbed wood-bentonite clay composites could be reused for adsorption of the cations.
Thermal degradation kinetic study of polystyrene/organophosphate composite
(Elsevier, 2018) Majoni, Stephen; Chaparadza, Allen
A 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.
Major 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.

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