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- ItemCharacterization, kinetics and thermodynamic evaluation of struvite produced using ferrochrome slag as a magnesium source(South African Journal of Chemical Engineering, 2023-10-24) Moyo, L.B.; Simate, G.S.; Hobane, N.; Dube, C.There is limited data on studies that have focused on the kinetics, thermodynamics, and characterization of struvite crystallization from alternative magnesium sources. This study focused on thermal analysis of struvite (produced using ferrochrome slag as a magnesium source) and the results indicated that the residual quantities of struvite were lower than the theoretical mass loss of struvite of 51.42%. When using ferrochrome slag (FCS) as the magnesium source, 47.9%, 47.4%, and 46.9% losses in mass were observed for heating rates of 5◦C/min; 10◦C/min and 15◦C/min respectively. The mean activation energies for struvite produced using FCS were deduced using isoconversional kinetic methods and ranged from 49.81to 56.20 kJ/mol which is very similar to the activation energies deduced using MgCl2. The study also focused on the surface morphology, and particle size of the final product at different pH and N:P ratios. The final particle size distribution of the product was significantly influenced by the solution pH. To improve the crystal growth kinetics for both MgCl2 and FCS, a high ratio of N:P molar ratios should be adopted. The product's highest median particle size was obtained using FCS as the magnesium source at a low pH. Median particle size increased with decrease in pH, at a pH of 7.5 the recorded median particle size was 96 µ m whilst, the lowest was 31 µ m at a pH of 9.5. The highest percent of fines (<10 µ m) was recorded at a pH of 9.5 using FCS as magnesium source in the metastable region of struvite precipitation whereas at a pH of 7.5 no fines (<10 µ m) were recorded. SEM images confirmed that the struvite underwent morphological changes when prepared with FCS in comparison to that produced using MgCl2. The surface morphology of the finished product demonstrated the presence of irregular shaped particles, due to presence of impurities. The kinetic data showed that struvite precipitation was limited by the chemical reaction step. Model fitting was used to determine the reaction control mechanism and the average activation energies obtained by four model free methods were FWO (56.2), KAS (51.67) Starink (49.61) and Tang (49.81) kJ/mol, indicating that the FWO method was the least accurate method. The thermodynamic data indicated that the thermal degradation of struvite crystals has a high degree of disorder, and the process is endothermic, irreversible, and non-spontaneous.
- ItemKinetic and Equilibrium Modelling of Lead, Zinc and Copper Ions Sorption from Aqueous Solution Using Charcoal Fines(ournal of Applied Science and Technology (AJAST), 2024-06-30) Mungwari, C.P.; Chipangura, W.; Ndlovu, B.; Madziwa, T.N.; Simende, C.K.; Nyenyayi, K.; Chewu, C.C.The potential of chemically modified charcoal fines UCF (unmodified charcoal fine) and MCF (modified charcoal fines) as low cost adsorbents for the removal of Pb2+, Cu2+ and Zn2+ ions from aqueous solution was studied. MCF was prepared by chemical modification of UCF with HNO3 and KOH followed by pyrolysis. The factors influenced the effectiveness of biosorption process were pH, contact time, initial metal concentration, temperature and adsorbent dosage. FT–IR spectra confirmed the existence and interaction of the adsorbents with the effluent pollutants. MCF exhibited optimum pH, temperature, contact time, initial metal ion concentration and biosorbent dosage values of 5, 35 0C, 90 minutes, 15 mg/L and 2 g, respectively. UCF exhibited optimum pH, temperature, contact time, initial metal ion concentration and biosorbent dosage values of 6, 35 0C, 100 minutes, 20 mg/L and 2.5 g, respectively. The adsorption isotherm modelling using both adsorbents showed that the equilibrium data conformed more to Langmuir than the Freundlich model. Kinetic studies showed that the adsorption processes followed a pseudo-second order kinetic model. Thermodynamic studies confirmed the spontaneity and feasibility of the adsorption process. The results showed that both adsorbent have the potential to be applied as alternative low cost biosorbent.
- ItemChallenges and Drivers of Industrialist Propensity Among Chemical Engineering Students in STEM Institution in Zimbabwe: Towards A Conceptual Framework(International Journal of Environment, Engineering and Education, 2024-04-24) Nkala, B.; Sibanda, V. M.; Ndhlovu, J.; Hobane, L.; Singh, SNUST in Zimbabwe grapples with a significant challenge. Despite enrolling many students in chemical engineering, the nation lacks operational industries. Consequently, graduates often encounter difficulties securing employment or attachment placements post-graduation. This underscores the critical need to foster student entrepreneurship, encouraging innovation and idea generation. The study employed a mixed-methods research design to address this issue, combining qualitative and quantitative methodologies. The quantitative aspect utilized a quasi- experimental pre-test and post-test design, while the qualitative component involved conducting focus group interviews with chemical engineering students in the experimental group. The findings from both approaches complemented each other, providing a comprehensive understanding of the factors influencing entrepreneurial propensity among NUST chemical engineering students. Data collection involved distributing research instruments and questionnaires to NUST students and individuals associated with the mining and pharmaceutical industries. The collected data were then entered into an Excel spreadsheet, allowing for the recording of respondents' numbers alongside their respective responses. The study applied descriptive statistics to evaluate responses and their alignment with research objectives, revealing barriers to entrepreneurial inclination among NUST chemical engineering students, such as limited resources, risk aversion, inadequate entrepreneurial education, and cultural norms. Students benefited from personal motivation, a supportive educational atmosphere, networking opportunities, and exposure to innovative ideas. These factors nurtured self-determination, social networking, and an entrepreneurial mindset. To foster entrepreneurial spirit among NUST chemical engineering students, the study suggests educational reforms, mentorship programs, and potential policy changes create an enabling environment, empowering students to pursue entrepreneurship and contribute to economic growth.
- ItemPressurized torrefaction of waste biomass to improve bio coal quality: Synergistic effect between animal waste and wood chips(Elsevier, 2025-04-19) Tshuma, N.M.; Moyo, L.B.; Danha, G.; Mamvura, T.A.; Simate, G.S.; Artur, C.D.; Charis, G.This study aims to investigate the effect blending waste material to improve its fuel properties using pressurized torrefaction. This research explored the benefits of blending animal waste with wood chips to produce a bio-coal with improved fuel properties. The process conditions investigated were temperature and pressure intervals of 200◦C to 280◦C and atmospheric pressure (AP) to 4MPa, respectively. The results showed that an increase in temperature and pressure improved the fixed carbon content of the blend almost threefold from 19.87 % to 66.93 % and the higher heating value (HHV) to 27.32MJ/kg from 13.90MJ/kg at mild torrefaction temperature of 280◦C and gas pressure of 4MPa compared to atmospheric pressure conditions and the lowest temperature investigated. The HHV increased primarily due to a release of bound and unbound moisture and volatile matter. Wood chips had an HHV of 27.00MJ/kg at a torrefaction temperature of 280◦C due to the decomposition of hemicellulose and cellulose which enhanced the thermal stability, fixed carbon content and calorific value. However, animal waste had the least incremental increase in HHV (16.45MJ/kg) due to a high initial content of volatile matter and moisture. The improved properties of the blend of materials indicated that pressurized torrefaction was effective in increasing fixed carbon content through secondary polymerization reactions. Moreover, it facilitated the decomposition of cellulose at a lower temperature than the typical range of 315-400◦C if conducted at atmospheric pressure. This study elucidates the notable role of the synergistic effects of blending feed materials prior to torrefaction towards improving the properties and pyrolysis performance of biomass components.
- ItemApplication of amine-modified tannins gels as coagulants in wastewater treatment(Research Square, 2024-08-28) Thelmmer, M.; Ncube, S.; Moyo, L.B.; Mamvura, T.A.; Danha, G.; Simate, G.S.; Tshuma, N.Tannin (T) is an organic substance that may potentially be used as an inexpensive, environmentally friendly, and effective bio-coagulant to remove impurities from residential and commercial wastewater. In this study, bio-coagulants were prepared using tannins obtained from the wattle tree (Acacia mearnsii). The bio-coagulants were modified using formalin and optionally, ethanolamine (ETA) and ammonium chloride (NH 4 Cl) as amine sources through the Mannich Reaction scheme. Three coagulants were prepared, T-ETA modified tannin, T-NH 4 Cl modified tannin and a mixture of T-ETA: T-NH 4 Cl in molar ratio 1: 1. Aluminium sulphate [Al 2 (SO 4) 3], a metal-coagulant was also used as the standard for comparison. The three coagulants were tested at varied concentrations (500–1250 mg/L) using jar tests on laundry wastewater to see their effect on remediation of wastewater. A mixture of bio-coagulant T-NH 4 Cl and T-ETA was most effective with highest removal efficiencies for turbidity (94%), COD (85%), Total solids (87%) and nitrates (99%). For colour removal T-NH 4 Cl modified tannin showed the highest removal efficiency of 92%. The results support the use of cheaper and environmentally friendly amine modified tannin-based flocculants in laundry wastewater treatment as they showed less toxicity on the treated water.