South African Journal of Chemical Engineering最新文献

Biofilter technology has played a significant role over several decades in providing clean air through removal of Volatile Organic Compounds (VOCs) and odor causing chemicals such as hydrogen sulfide from industrial polluted airstreams. Biofilters where biological oxidation process takes place are designed and installed in numerous industrial facilities including chemical manufacturing, food processing, solid waste recycling and wastewater treatment plants to control emissions of VOCs, and odors in order to comply with the air emission regulations and to provide clean breathable air. Biofilter mathematical models under steady-state and transient conditions are essential in order to design, scale-up and predict biofilter performance under different operating conditions. Similarly, Artificial Intelligence (AI) through the use of Artificial Neural Network (ANN) modeling of biofiltration process is also becoming important. This research provides a detailed discussion and review of the recent (i.e., the last two decades) and important studies related to ANN, steady-state and transient biofilter models.

The present study investigated the effect of operational flux on the performance of hollow fiber anaerobic membrane bioreactors (HF-sAnMBR) during treatment of synthetic wastewater containing diazo dye. Two extreme operational flux value, which were 56.92 LMH and 3.21 LMH in reactor 1 (R-1) and reactor 2 (R-2), respectively, were chosen and the systems were operated at an extended time of 128 days. Under high initial flux, total chemical oxygen demand (t-COD) and soluble chemical oxygen demand (s-COD) removal in HF-sAnMBR reached an average of 76.27 ± 3.26 % and 77.20 ± 2.97 %, respectively. In contrast, the AnMBR operated at a lower flux exhibited 62.91 ± 3.10 % t-COD and 65.56 ± 1.74 % s-COD removal. The mean decolorization was 82.88 ± 7.20 % and 76.18 ± 13.96 % in R-1 and R-2, respectively. While R-1 showed excellent performance from the first day of operation, R-2 required 60 days to achieve comparable performance. However, biofouling was aggravated in R-1, which led to frequent membrane cleaning. Despite the operational hurdles, the fast deposition of biofoulants on R-1 might be responsible for its high COD and color removal, as the microorganisms on the membrane surface actively degraded organics and dyes. UV–visible spectroscopy and gas chromatography-mass spectrometry analyses demonstrated the breakdown of azo bonds and further confirmed the presence of benzene-based aromatic intermediates and several mineralized byproducts. Microbial analysis revealed a shift at the community level, as the inoculum was abundant in the phylum Chloroflexi (48 %), which shifted to Firmicutes (R1:49 %; R2:46 %), with Clostridium as the major genus, which is attributed to azo dye-degrading bacteria. Anaerobic sulfate-reducing bacteria may contribute significantly to aromatic hydrocarbon degradation and further dye mineralization.

In an attempt to model and optimize the biodiesel production from the binary oil blends, a BTO₄₀ obtained from the mixture of Dennettia tripetala (DTO) and Luffas cylindrical (LCO) oilseeds was employed in a double-stage microwave-assisted batch process (DSMABP). The DTO₄₀ was esterified with iron (III) sulfate (Fe₂(SO4)₃) and then transesterified with catalyst selectivity between calcined fermented sweet corn stock (CFCS) and calcined non-fermented sweet corn stock (CNFCS). Catalyst characterization was carried out using analyzers, while process modeling and optimization were carried out using statistical tools. The produced biodiesel qualities were evaluated, and the catalyst potential was tested by a catalyst reusability test. Results show that a BTO₄₀ was suitable for maximum biodiesel yield of 98.92% (wt./wt.) with HHV of 43.84 MJ/kg, CN of 79.73, flash point of 120 °C, cloud point of -3 °C, pour point of -6 °C, cold filter plugging point of +2 °C, oxidative stability of 4.6 h, and carbon residue of 0.02% nm. The statistical modeling and optimization by RSM_I-Optimal predicted a mean value of biodiesel to be 99.28% (wt./wt.), the ANN_GA predicted a mean biodiesel yield of 99.78% (wt./wt.), and γ_GCFW predicted 99.82% (wt./wt.), respectively, at different variable conditions. These values were validated in triplicate, and the average means were obtained as 98.57% (wt./wt.), 99.69% (wt./wt.), and 99.71% (wt./wt.), respectively. Catalyst usability tests show DFSCS has high alkali potential as a base catalyst. The produced biodiesel properties are in total agreement with the recommended biodiesel standard. The study concluded that BTO₄₀ treated with a 0.1 M Fe₂(SO4)₃ solution in a base-catalyzed calcined fermented sweet corn stock for biodiesel synthesis can be used as an alternative fuel.

In this study, a novel green adsorbent, Tabernaemontana divaricata leaf powder (TD), was prepared, and its efficacy in removing malachite green (MG) dye from water, along with the associated mechanism and kinetics, was systematically evaluated for the first time. Characterization of TD was carried out using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Optimization of MG dye removal was conducted by varying parameters such as pH, initial dye concentration, contact time, and TD dosage. Results demonstrated that TD exhibited a high adsorption capacity for MG dye (5.2131 mg.g⁻¹), achieving a maximum removal efficiency of 89.5 % under optimized conditions: pH 7.0, initial dye concentration of 20 ppm, contact time of 120 min, TD dosage of 4 g/L, and temperature of 28.1 °C. Kinetic and isotherm models were applied to analyze the experimental data, revealing that the adsorption process most accurately followed Ho's pseudo-second-order kinetic model (R² = 0.999). The high heats of adsorption observed in the isotherm study suggest prominent electrostatic interactions between adsorbate molecules and the surface, governing the chemisorption mechanism that dominates at the solid-liquid interface. This study underscores the potential of Tabernaemontana divaricata (jasmine) leaf powder as a cost-effective, environmentally friendly, and efficient adsorbent for the remediation of MG dye-contaminated water.

The study focused on investigating the impact of various environmental parameters on the production of Scenedesmus, a unicellular alga known for its industrial and food value. The parameters studied included production method, temperature, lighting period, light intensity, and pH, with a particular emphasis on suspension and biofilm production methods. The results highlighted optimal conditions for different aspects of production, such as cell density, biomass production, lipid production, and biodiesel production. Specifically, the findings indicated that the highest cell density was achieved at a temperature of 25 °C, light intensity of 3000 lux, lighting period of 16 h, and pH of 8. For biomass production, the optimal conditions were a temperature of 25 °C, light intensity of 3000 lux, lighting period of 18 h, and pH of 9. The greatest lipid production was observed at a temperature of 20 °C, light intensity of 4000 lux, lighting period of 18 h, and pH of 8. Moreover, the highest biodiesel production was recorded at a temperature of 25 °C, light intensity of 3000 lux, lighting period of 18 h, and pH of 8. Notably, the study found that the biofilm production method outperformed the suspension method across various parameters, including cell density, biomass production, lipid production, and biodiesel production. These results contribute to the existing knowledge of optimal conditions for microalgae production and underscore the potential of Scenedesmus in industrial and food applications.

Durian (Durio zibethinus) is highly consumed seasonal fruit that generates abundant waste in the form of peel. Durian peel can serve as an effective adsorbent because it is rich in cellulose–lignin. This waste has potential applications in the chemical industry, such as using durian peel to purify crude glycerol. This research studied durian peel as an adsorbent in the form of activated carbon in the purification of acidified crude glycerol. The purification process begins with the acidification process of crude glycerol using concentrated acid with a mole ratio of phosphoric acid:glycerol (n/n) of 0.5:1, 1:1, 1.5:1, 2:1, and 2.5:1. The adsorption process by carbonization and activated of durian peel using 0.1 N KOH as adsorbent with a mass percentage ratio of adsorbent:crude glycerol (%wt) of 5 %, 10 %, 15 %, 20 %, and 25 %, and stirred using a magnetic stirrer at a speed of 250 rpm for 2 h. The adsorbent utilized has a carbon-rich content of as much as 80.6 % based on Energy Dispersive X-ray analysis. The highest glycerol purity obtained at 96.26 % is achieved at phosphoric acid:glycerol mole ratio of 1:1 and adsorbent:glycerol mass ratio of 25 %. This result also matches the analysis by gas chromatography. Thus, the others test of the purified glycerol, such as density of 1.267 g/cm³, water content of 1.6 %, ash content of 0.2 %, and matter organic non-glycerol of 1.94 %, are in accordance with the glycerol standard BS 2621:1979.

The application of the expanded polystyrene (EPS) waste to the functional material is still a challenge. The hydrophobic property of polystyrene has a potential to create a superhydrophobic surface. Here, we use expanded polystyrene waste to coat surfaces in two different ways—spray coating and dip coating—to produce superhydrophobic surfaces for food packaging. The ZnO was employed to make the surface rougher. However, the combination of ZnO and EPS waste produces only a hydrophobic surface. For spray coating and dip coating, the maximum water contact angle is 119° and 125° respectively. The scanning electron microscope (SEM) picture reveals many holes that increase the surface's roughness. The hydrophobic surface significantly cuts down on cleaning time. According to the food packaging parameter test mandated by the Indonesian Food and Drug Administration (BPOM) (BPOM regulation No. 20, 2019), the coating complies with heavy metals and ethanol stimulant migration testing requirements for food packaging. However, the migration condition in acetic acid stimulant surpasses the maximum standard. The total migration in 3% acetic acid stimulant (40°C for 10 days) is 22.95 mg/dm² while the maximum value is 10 mg/dm².

The limited supply of fossil fuels towards carbon neutrality has prompted massive efforts to replace fossil fuel vehicles with electric vehicles. This research investigates the recovery of lithium in leaching solutions through solvent extraction experiments using several experimental parameters such as ratio, extraction time, solvent concentration, type of diluent and stirring speed. Lithium leaching in Sidoarjo mud has been carried out using a hydrometallurgical process followed by solvent extraction. The solvent used is Di-(2-ethylhexyl) phosphoric acid (D2EHPA) with Kerosene and vegetable oil as diluents. The Taghuchi L8 orthogonal arrangement was carried out to identify process parameters that influence the concentration of lithium extract. The influence of parameters was examined by Analysis of Variance (ANOVA) through contribution percentages. Investigation of optimized lithium extraction is a ratio of 1:1, extraction time of 30 min, solvent concentration of 1 M, type of vegetable oil diluent and stirring speed of 300 rpm. Thus, the results show that ratio is the most influential factor with a Lithium contribution percentage of 67.22 %.

The role of mesoporous solid acid aluminosilicate in the oleic acid deoxygenation was elucidated using ZSM-5 and Al-MCM-41 impregnated with Ni. The mesoporous supports were synthesized using a similar initial Si/Al ratio but employing different templates to vary the mesopores. ZSM-5_T produced interparticle mesopores when using TPAOH (tetrapropylammonium hydroxide) as a template. Meanwhile, ZSM-5_S with a well-defined intraparticle mesoporous channel was formed using a silicalite template. Al-MCM-41 synthesized without a template produced one-dimensional highly ordered mesoporous channels. The arrangement of mesoporosity in aluminosilicate determined the mechanistic pathway of oleic acid conversion into hydrocarbon. Oleic acid underwent primary thermal cracking into carboxylic acid before progressing into the subsequent decarbonylation reaction. The diesel hydrocarbon yield was enhanced following the order of Al-MCM-41>ZSM-5_S>ZSM-5_T>blank reaction. Large intraparticle mesoporosity produced long-chain carboxylic acid from catalytic cracking of oleic acid, which was subsequently deoxygenated into long-chain hydrocarbons.