Research Articles (Chemical Engineering)
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Item Liquid-liquid equilibrium studies for potential solvents/cosolvents for the separation of aromatics and alkanes(American Chemical Society, 2025-06) Paile, Blessing Mcebo; Narasigadu, Caleb; Seedat, NaadhiraLiquid–liquid equilibria (LLE) data for ternary systems of n-heptane + a solvent mixture + toluene were measured at 298.15 and 313.15 K and 101.3 kPa. The solvents investigated are mixtures of N-methylpyrrolidone and glycerol, with ratios of N-methylpyrrolidone to glycerol of 90:10, 70:30, and 50:50. LLE measurements were carried out using the direct analytical method, and the composition analysis was performed using gas chromatography. The effectiveness of the solvent mixtures of N-methylpyrrolidone and glycerol in extracting toluene from n-heptane was evaluated by determining the solvent selectivity and capacity and evaluating the extent of the two-phase region. All systems investigated were found to exhibit type I LLE behavior. The binodal curves were correlated to the Hlavatý β function and log γ equations. The tie-lines were correlated with the NRTL and UNIQUAC activity coefficient models. A comparison of the root-mean-square deviation (rmsd) showed that the NRTL model provided a better correlation for all systems.Item Technical and financial evaluation of an emerging thermochemical technology for sustainable management of municipal wastewater sludge(IWA Publishing, 2024-12) Zvimba, John Ngoni; Musvoto, Eustina; Kholisa, Buyisile; buyisile.kholisa@tuks.co.zaThe management of municipal wastewater sludge is a significant challenge for wastewater management, particularly the need to manage and dispose of the sludge in an environmentally friendly and sustainable manner. The emergence of stricter regulations regarding landfill disposal of wastewater sludge necessitates the need for alternative options for municipal wastewater sludge management, with thermochemical technologies potentially contributing towards achieving carbon neutrality goals and fostering sustainable development. This study sought to address these challenges through a technical and financial evaluation of a pilot-scale emerging thermochemical technology, the enhanced hydrothermal polymerization to provide adequate understanding of the technology's feasibility regarding its application for municipal wastewater sludge volarization into a multi-use hydrochar. The study findings indicated that the enhanced hydrothermal polymerization-generated hydrochar exhibited significant energy content compared to wastewater sludge, suggesting the potential use of the hydrochar as an energy source. The preliminary designs of a full-scale greenfield installation and retrofit processing 50 t/d and 35 t/d dry sludge, respectively, were evaluated to be technically feasible. Furthermore, on the basis of preliminary designs, the enhanced hydrothermal polymerization technology was determined to be the most financially feasible option, also offering other unique advantages over well-established technologies currently used within municipal wastewater services.Item Usage of silica xerogel from African sugarcane leaves as a catalyst in biodiesel production through transesterification(American Chemical Society, 2025-06) Maseko, Ncamisile Nondumiso; Enke, Dirk; Owolawi, Pius Adewale; Iwarere, Samuel Ayodele; Oluwafemi, Oluwatobi Samuel; Pocock, JonathanBiodiesel was produced through transesterification from canola oil and methanol in the presence of silica xerogel derived from sugar cane leaves as a solid catalyst. The transesterification reaction was carried out at 65 °C in a batch-type reactor where a three-neck round-bottom flask was used as a reaction vessel with a reflux setup. Reaction time, methanol to oil ratio, and weight percentage of the catalyst were varied to optimize the biodiesel yield. The xerogel catalyst was characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES), nitrogen physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The produced biodiesel was characterized using gas chromatography-mass spectroscopy (GC-MS), Fourier transform infrared spectroscopy (FTIR), and a viscometer. The synthesized catalyst was found to operate as a true heterogeneous catalyst, since it preserved its solid nature and did not leach into the reaction medium. A biodiesel yield of 96.9% was achieved under optimal reaction conditions of 60 min reaction time, 6:1 methanol to oil ratio, and 3 wt % catalyst loading. The produced biodiesel was found to have a mixture of both saturated and unsaturated fatty acid methyl esters and had physical properties that met the ASTM and EN standards. The investigated catalyst was found to have a potential of being recycled up to 3 times, which positively affects the biodiesel production costs.Item Melt processing of cellulose acetate for controlled release applications - a review(Wiley, 2025) Mphateng, Thabang N.; Mapossa, António Benjamim; Mokhena, Teboho; Ray, Suprakas Sinha; Sundararaj, UttandaramanCellulose acetate (CA) has garnered considerable industrial and research interest due to its sustainable properties, such as biodegradability and biocompatibility. Despite these attractive properties, CA is difficult to process using traditional melt processing techniques. This is due to its high crystallinity and a glass transition temperature that exceeds the thermal degradation temperature. Therefore, different additives have been explored to overcome these issues. This review explores recent trends in the use of melt-processed CA materials for encapsulating and controlling the release of active compounds. It highlights the advancements made over the past decade in processing CA-based materials using thermoplastic techniques. Additionally, the review discusses the properties of these materials, including biodegradation, photodegradation, and solubility, which are important for delivering active agents. Finally, it provides an overview of the challenges and prospects for CA-based materials processed through thermoplastic processing methods.Item Photocatalytic degradation enhancement of dye on Bi12O17Cl2 through Er3+ and Yb3+ doping(Italian Association of Chemical Engineering, 2025-07) Ogbeifun, Osemeikhian; Tichapondwa, Shepherd Masimba; Chirwa, Evans M.N.Please read abstract in the article.Item Interfacial solar steam generator based on reduced graphene oxide/polyurethane monolith for efficient seawater desalination(Italian Association of Chemical Engineering, 2025-07) Manoto, Bontle A.; Bezza, Fisseha Andualem; Tichapondwa, Shepherd Masimba; Chirwa, Evans M.N.Seawater desalination using renewable energy sources is a promising solution to combat global water scarcity. In this study, the development and performance of an interfacial solar steam generator (ISSG) based on a reduced graphene oxide/polyurethane (rGO/PU) monolith is reported. Graphene is a hexagonal lattice 2D structure of sp2 hybridized carbon atom. It has excellent properties such as high thermal conductivity and high specific surface area making it a suitable candidate for thermal desalination. Pristine graphite was oxidised following Tour`s method. The rGO/PU monolith was fabricated through a hydrothermal self-assembly process and characterized using Raman spectroscopy, SEM, XRD, FTIR, and BET. Under 1 sun illumination, the ISSG achieved an evaporation rate of 1.34 kg·m?²·h?¹ and a photothermal conversion efficiency of 93%. This porous device effectively addressed the issue of energy localization, heat management, anti-scaling, and salt rejection. Our results demonstrate that the rGO/PU-based ISSG is a promising solution for efficient seawater desalination, and upscaling is recommended for practical applications.Item Effect of cyanide as a nutrient source on bacteria, Bacillus Cereus, for use in bioleaching of gold tailings(Italian Association of Chemical Engineering, 2025-07) Mpeta, Miranda; Tendenedzai, Job Tatenda; Tichapondwa, Shepherd Masimba; Chirwa, Evans M.N.; u24054276@tuks.co.zaPlease read abstract in the article.Item Occurrence, ecotoxicity, and photocatalytic remediation of antiretroviral drugs in global surface water matrices(MDPI, 2025-04) Ngwenya, Phephile; Tabana, Lehlogonolo Shane; Tichapondwa, Shepherd Masimba; Chirwa, Evans M.N.; evans.chirwa@up.ac.zaThe increasing presence of pharmaceuticals, particularly antiretroviral drugs (ARVs), in wastewater has raised concerns regarding their environmental and health impacts. Photocatalysis, driven by advanced photocatalysts, such as coloured TiO2, ZnO, and composites with carbon-based materials, has shown promise as an effective method for degrading these pollutants. Despite significant laboratory-scale success, challenges remain in scaling this technology for real-world applications, particularly in terms of photocatalyst stability, the formation of toxic degradation by-products, and economic feasibility. This paper explores the current state of photocatalytic degradation for ARVDs, emphasizing the need for further research into degradation pathways, the development of more efficient and cost-effective photocatalysts, and the integration of photocatalysis into hybrid treatment systems. The future of photocatalysis in wastewater treatment hinges on improving scalability, reactor design, and hybrid systems that combine photocatalysis with traditional treatment methods to ensure comprehensive pollutant removal. Innovations in catalyst design and reactor optimization are essential for advancing photocatalysis as a viable solution for large-scale wastewater treatment.Item Tailoring biphasic high-halogen SEI via organochlorine isomeric effect for stable lithium metal anodes(Elsevier, 2025-12) Liang, Yangjie; Liu, Fangfang; Ren, Jianwei; Wang, Xuyun; Wang, Hui; Song, Jimei; Feng, Lijuan; Wang, Rongfang; jianwei.ren@up.ac.zaThe fragile nature of the solid electrolyte interphase (SEI) formed on lithium metal anodes, particularly due to irregular lithium deposition and sluggish ion transport, presents a major challenge to the wider deployment of lithium-sulfur (Li-S) batteries. In this study, a high halogen-containing SEI of the lithium anode was prepared and finely tuned using the variance in chlorine substitution sites as a regulatory mechanism with the positional isomerism of dichloropyridines (DCPs). Remarkably, a highly halogenated inorganic layer was composed predominantly of LiF and LiCl, reaching up to 62 % coverage, which not only mitigated lithium dendrite proliferation and accommodated volume changes during cycling but also facilitated efficient Li+ ion conduction. Under demanding conditions with a high sulfur loading of 3.0 mg cm−2 and a lean electrolyte ratio (electrolyte to sulfur ratio = 13.3 μL mg−1), the cells retained a capacity of 520.65 mA h g−1 after 300 cycles at 0.5 C.Item Sustainable microbial lead removal using an upflow anaerobic sludge blanket reactor : advancing eco-friendly solutions for heavy metal remediation(MDPI, 2024-12-03) Manzini, Bayandza M.; Cilliers, Carla; Tendenedzai, Job Tatenda; Henaklaus, Nils H.; Chirwa, Evans M.N.; Brink, Hendrik GideonThis study investigates the use of a UASB (Upflow Anaerobic Sludge Blanket) reactor operating under continuous anoxic conditions to remediate Pb(II) contamination in aqueous environments. Two experimental runs were conducted to evaluate the microbiome’s performance in removing Pb(II) at varying concentrations, ranging from 80 to 2000 ppm, while monitoring nitrate and Pb(II) levels. Metabarcoding of the 16S rRNA gene was done to understand the detoxification mechanisms utilised by the microbial community in Pb(II) removal. The system demonstrated high robustness, achieving up to 99% Pb(II) removal efficiency with sufficient nutrient availability, particularly at 15 g/L yeast extract (YE), compared to lower nutrient levels of 5 g/L YE. Denitrification was identified as the dominant mechanism of detoxification, supported by additional processes such as biosorption, sulfur-reducing bacterial activity, bioprecipitation, and bioremoval. Analysis of the precipitate recovered from the reactor indicated the presence of elemental lead, PbS, and PbO, highlighting the potential for lead recovery. These findings suggest that the system not only effectively removes Pb(II) from contaminated environments but also offers a sustainable pathway for lead recovery through smelting, making it a promising circular bioremediation strategy. The results indicate that this biological approach is a viable solution for lead pollution and recovery in industrial applications.Item Production and characterization of densified briquettes from nanocomposite biochar-cellulose nanocrystal (Biochar-CNC) reinforced with polyvinyl alcohol (PVA)(Springer, 2025-05) Ayaa, Fildah; Oyedotun, Kabir Oyeniran; Lubwama, Michael; Iwarere, Samuel Ayodele; Daramola, Michael Olawale; Kirabira, John Baptist; michael.daramola@up.ac.zaBiomass briquettes are still important to communities in developing nations because they are cheap, sustainable, and generated from solid waste that can be utilized to produce energy. However, the low quality of the briquettes when compared to traditional cooking fuels hampers their widespread adoption; yet, there is an opportunity for expanding the briquette market due to the rise in charcoal prices, increasing scarcity of forest resources, and more environmental awareness among consumers. The main objective of this study was to develop a bio-based briquette with improved combustion characteristics through the use of an innovative binder. A novel nanocomposite briquette (biochar/cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) was produced using the solution casting method, with CNC/PVA nanocomposite as a binder. A total of five (5) nanocomposite briquettes having biochar-to-binder ratios of; 90:10, 80:20, 70:30, 60:40, and 50:50 and designated as BCP (9/1), BCP (8/2), BCP (7/3), BCP (6/4) and BCP (5/5), respectively were developed. The nanocomposite briquette samples were characterized for thermal stability, mechanical properties, elemental composition, surface morphology, proximate composition, and combustion characteristics using established methods. The produced briquettes had a very low ash content of less than 2% and a low average moisture content of 8%. The surface morphology of the briquettes revealed a rough and porous structure that can enhance combustion. The BCP (9/1) briquette had the highest calorific value of 27 MJ/kg, followed by BCP (8/2) and BCP (7/3) which had a calorific value of 26 MJ/kg. The BCP (7/3) nanocomposite briquette was the most thermally stable, with the lowest onset degradation temperature (220 °C), highest peak temperature (514 °C), least char residue, and the most compressive strength of 11 MPa. The BCP (9/1), BCP (8/2), and BCP (7/3) nanocomposite briquettes also satisfied the combustion indices criteria, demonstrating their potential to replace coal in industrial applications. The thermal degradation and kinetics of the nanocomposites were studied using TGA-DTG techniques at three different heating rates; 5 °C/min, 10 °C/min, 20 °C/min in an oxygen environment. The kinetic parameters, that is, the activation energy and pre-exponential factor were calculated using the Coats-Redfern method. The combustion of the briquettes happened in three distinct phases with a higher activation energy required at higher heating rates to initiate the first stage of combustion. Also, up to 40% of the binder can be added without affecting the ignition, combustion, and burn-out properties of the briquette. This study, therefore, demonstrates that Biochar-PVA-CNC nanocomposite briquettes are a potential biofuel for industrial and household applications.Item Advancements in ether-free poly(arylene) proton exchange membranes : pyridine and piperidine-based architectures for high-temperature fuel cells(American Chemical Society, 2025-08) Kumar, Divya; Ravi, Murali; Liu, Huiyuan; Zhang, Weiqi; Xu, Qian; Ren, Jianwei; Su, HuanengHigh-temperature proton exchange membrane fuel cells (HT-PEMFCs) provide a number of benefits over low-temperature systems, including improved reaction kinetics and a greater ability to tolerate impurities. However, developing durable membranes remains a key challenge due to the competing demands of phosphoric acid (PA) retention, thermal stability, and high proton conductivity in the absence of excessive PA doping. While polybenzimidazole (PBI) membranes demonstrate strong performance, their susceptibility to mechanical degradation and oxidative instability at high temperatures have spurred the search for superior alternatives. This review highlights pyridine/piperidine-based membranes as a promising solution, leveraging heterocyclic additives (e.g., pyridine and piperidine) to enhance durability and functionality. Key chemical modifications including side-chain and main-chain adjustments are examined for their influence on the polymer structure and performance. Additionally, the microporous architecture and intermolecular interactions between functional groups are analyzed to elucidate their roles in improving the conductivity and stability. Compared to commercial PBI membranes, pyridine/piperidine-based alternatives exhibit superior performance stability, positioning them as strong candidates to advance HT-PEMFC technology toward sustainable energy applications.Item Highly effective antibiotic mineralization via laccase-immobilized nanocomposite beads coupled with fungal phycoremediation(Elsevier, 2025-03) Kyomuhimbo, Hilda Dinah; Feleni, Usisipho; Brink, Hendrik Gideon; deon.brink@up.ac.zaPlease read abstract in the article. HIGHLIGHTS • Laccase enzyme was successfully immobilized on synthesized ZnONPs-CS-PVPP and Ag@ZnONPs-CS-PVPP composite beads. • The biocatalyst demonstrated superior catalytic activity in degradation of tetracycline and Ciprofloxacin in wastewater. • Phycoremediation using Aspergillus sp. was used to achieve mineralization of the degradation by-products. • The plausible mechanisms of degradation of tetracycline and Ciprofloxacin were proposed • The antibiotic activity of tetracycline, ciprofloxacin and degradation byproducts was evaluated.Item An overview of antifogging nanocoatings : recent developments and application(Elsevier, 2024-12) Sanni, Omotayo; Ren, Jianwei; Jen, Tien-Chien; jianwei.ren@up.ac.zaTransparent materials are essential to our daily lives. It's very well recognized that their use in windshields, cars, windows, mirrors, and eyewear makes our everyday tasks more comfortable. In addition to these, several other instances may be found in the culinary, medical, and solar industries, among other spheres of human endeavor. Unfortunately, under typical operating conditions, this material experiences fogging owing to the unavoidable condensation of water vapor on solid surface. Researchers are becoming more and more interested in antifogging nano-coatings with remarkable water repellence as a result of the growth of the coating industries and material engineering. Numerous compounds have been created by researchers thus far to prepare antifogging films. There have been reports on the mechanisms and guidelines for the creation of these agents by various technologies as a result of the core requirements of various fields. We present the latest developments in antifogging nanocoatings and antifogging performance test procedures in this review. Additionally, there has been a focus on offering understanding of the latest advancement in superhydrophobic coating through the application of nanotechnology. According to the literature, the reported antifogging films do not show sufficient results and continue to pose a practical issue that requires real-world application. As a result, antifogging techniques need to be improved further.Item Synthesis and evaluation of 3D nitrogen doped reduced graphene oxide (3D N@rGO) macrostructure for boosted solar driven interfacial desalination of saline water(Wiley, 2025-04) Bezza, Fisseha Andualem; Iwarere, Samuel Ayodele; Tichapondwa, Shepherd Masimba; Brink, Hendrik Gideon; Daramola, Michael Olawale; Chirwa, Evans M.N.; evans.chirwa@up.ac.zaPlease read abstract in the article.Item MIL-53(Al)-MOF sorbents in dispersive micro-solid phase extraction of penicillins from water(Elsevier, 2025-08) Skans, Inga; Dyosiba, Xoliswa Lindokuhle; Mnguni, Mthokozisi; Nomngongo, Philiswa NosizoPenicillin is an antibiotic that presents serious environmental risks because of its extensive use and ends up in our water bodies. This work presents the development and application of a dispersive micro-solid phase extraction (D-µ-SPE) procedure utilising the metal-organic framework MIL-53(Al) as a suitable adsorbent for preconcentration of piperacillin (PIP) and penicillin V (PNV) from water. The prepared MIL-53(Al)-MOF was characterised using various characterisation techniques. Following the extraction and preconcentration processes, a high-performance liquid chromatography-diode array detector (HPLC-DAD) was employed to separate and quantify PIP and PNV. The fractional factorial design (FrFD) and Box-Behnken design (BBD) were utilised to investigate parameters influencing the d-μ-SPE method for PIP and PNV. The maximum percentage recoveries were obtained under the following conditions: 5.5, 50 mg, 17.5 min, 1000 µL, and 10 min for pH, mass of adsorbent extraction time, eluent volume, and desorption time, respectively. High adsorption capacities for PIP (175 mg/g) and (217 mg/g) were achieved. The highest adsorption affinity toward zwitterionic analytes and quick kinetics of the adsorbent made the d-μ-SPE effective in extracting target analytes from various water matrices. The remarkable performance was attributed to electrostatic, hydrogen bonding, π–π and hydrophobic interactions. The pseudo-send order kinetics and Langmuir models described the adsorption data well. Under optimum conditions, the relatively low detection limits of 0.10–0.18 µg/L and wide linear range of 0.3–800 µg/L validated the effectiveness of the developed d-μ-SPE method. Applying the established d-µ-SPE/HPLC-DAD method to real water analysis verified its applicability and feasibility. In wastewater samples, PIP and PNV were found in the ranges of 0.71–1.12 µg/L for influent and 0.32–0.45 µg/L for effluent. PIP and PNV spike recoveries ranged from 91.7 % to 99.1 % and 93.2 % to 98.1 %, respectively, while the method's intraday and interday precision was <5 %. This work illustrates that the d-μ-SPE, in tandem with MIL-53(Al)-MOF, offers several advantages, including simplicity, rapidity and low solvent consumption for the recovery of penicillin from contaminated water sources. HIGHLIGHTS • MIL-53(Al)-MOF with attractive functional groups was successfully synthesized following a solvothermal techniques. • The prepared MIL-53(Al)-MOF has large adsorption capacities for piperacillin (175 mg/g) and penicillin V (217 mg/g). • The MIL-53(Al)-MOF/D-μ-SPE of piperacillin and penicillin V achieved high % recoveries with a range of 91–99 from environmental water and wastewater.Item Radioactivity distribution in soil, rock and tailings at the Geita Gold Mine in Tanzania(Elsevier, 2025-06) Mwimanzi, Jerome M.; Haneklaus, Nils H.; Bituh, Tomislav; Brink, Hendrik Gideon; Kiegiel, Katarzyna; Lolila, Farida; Marwa, Janeth J.; Rwiza, Mwemezi J.; Mtei, Kelvin M.Please read abstract in the article.Item Carbon nanofibers surface-exposed with highly active Ag nanoparticles for enhanced interfacial dynamics of lithium metal anodes(Wiley, 2025-06) Huang, Aoming; Huang, Hongjiao; Li, Shuo; Pan, Xiansong; Sun, Shichao; Su, Xueming; Geng, Hongbo; Li, Linlin; Maximov, Maxim; Ren, Jianwei; Peng, ShengjieLithium metal anodes (LMAs) are widely regarded as a crucial component for the next generation of high-energy-density lithium batteries. The extended pathways for lithium ion diffusion exacerbate concentration polarization, leading to dendrite growth in LMAs. Here, carbon nanofibers with surface-exposed high-activity silver nanoparticles (Ag@CNF) are achieved through the combination of electrospinning and ion exchange techniques, enhancing the interfacial dynamics during lithium storage. Compared to electrodes with encapsulated active sites, the self-supported and binder-free Ag@CNF significantly shortens lithium ion diffusion pathways, reduces nucleation overpotential, and promotes uniform ion diffusion and deposition. Furthermore, this unique structure induces a thinner solid electrolyte interphase (SEI) layer, and greatly reduces the apparent activation energy for charge transfer. Ag@CNF not only enhances atomic utilization efficiency of active centers but also optimizes performance in lithium metal batteries. Notably, assembled full cells demonstrate an excellent retention rate of 90% after 300 cycles at a high capacity of 1.5 mAh cm−2 and a low N/P ratio of 2.Item Enhanced photocatalytic efficiency of a novel GO/Bi2SO5/AgBr ternary heterojunction for the degradation of tetracycline and rhodamine B(Elsevier, 2025-06) Oluwole, Adewunmi Olufemi; Yusuf, Tunde Lewis; Tichapondwa, Shepherd Masimba; Daramola, Michael Olawale; Iwarere, Samuel Ayodele; samuel.iwarere@up.ac.zaPlease read abstract in the article.Item Preparation of hydrophilic PVDF membrane via blending with Fe3O4 nanoparticles and PVA for improved membrane performance in BTEX removal from wastewater(Elsevier, 2025-06) Enemuo, Ngozi; Richards, Heidi; Daramola, Michael OlawalePlease read abstract in the article.