South African Journal of Chemical Engineering最新文献

Empty Fruit Bunch (EFB) resulted from oil palm plantations and mills can be converted into ash through open combustion. The EFB ash then treated by simple calcination and used as a heterogeneous catalyst for biodiesel production. The characteristics of EFB ash were identified based on its elemental composition, porous structure, and active site size. The effectivity of the EFB ash as a catalyst was tested in a transesterification reaction of Refined Bleached Deodorized Palm Oil (RBDPO) with excess methanol (30 %-w) in various catalyst loads (in%-wt). The lab-scale experiments were conducted in a three-neck glass reactor, which was put on the hot plate stirrer at 450 rpm. The EFB ash performed the best as a catalyst by attaining optimal conversion at 65 °C for 1 h with a 16 %-wt of catalyst load. In this condition, most of the standard quality of biodiesel were complied with total glycerol under 0.24% and ester methyl contents up to 98.9 %. The characteristics tests showed that the properties and active side of the EFB ash are excellent after calcination at 600 for 5 h. The recyclability test of EFB ash as a catalyst showed high performance in two repetition cycles, each showing an increase in the yield of biodiesel, which was 92.21 % in cycle 2 and 91.23 % in cycle 3.

This study comprehensively evaluated HZSM-5 and USY-Zeolite as catalysts for producing biogasoline from crude palm oil through a catalytic cracking method, including uncertainty analysis. This study utilized HZSM-5 and USY-Zeolite as catalysts with crude palm oil (CPO) concentration ratios of 1:50, 1:75, 1:100, and 1:125. USY-Zeolite (19.06 %) exhibited a higher biogasoline yield than HZSM-5 (39.56 %) because of its optimal pore structure, as proven by N₂ physisorption characterization. Physicochemical characterization of biogasoline included flash point, viscosity, boiling point, and octane number measurements. Gas chromatography-mass spectrometry (GC–MS) was used to determine the chemical composition of biogasoline. An elevated catalyst ratio results in reduced liquid yields and biogasoline fractions. At a ratio of 1:125, the HZSM-5 catalyst produced the highest biogasoline yield (39.56 %). GC–MS analysis revealed that biogasoline contained various hydrocarbons and oxygenated compounds. Life cycle assessment (LCA) also demonstrated that this method can reduce the scarcity of mineral and fossil resources by 85 % and 35 %, respectively. Biogasoline's physical and chemical characteristics are significantly impacted by the type of catalyst and its various modifications. This study provides evidence that the catalytic cracking technique is suitable for producing biogasoline from CPO and yields positive results.

Composite materials made from natural ingredients are currently being developed by researchers as materials that are more environmentally friendly. Hybridization techniques used in making composite materials continue to progress, involving the combination of several raw materials with similar or different properties, such as organic/organic, organic/inorganic, and inorganic/inorganic. In this research, coconut fiber which is an organic material is combined with fly ash which is an inorganic material. The contrasting properties of these two raw materials prompted the evaluation of their combination by including a silane coupling agent, which facilitates the bonding of organic and inorganic components. The essence of this research is to test the effect of adding silane coupling material on several parameters, namely physical properties (density, water absorption, and thickness swelling), mechanical properties (tensile strength, tensile modulus, elongation, and flexural strength), and thermal properties. To prepare coconut fiber, alkaline treatment is used to remove hemicellulose and lignin. Then, the coconut fiber was soaked in a 5 % vinyltrimethoxysilane (TVS) solution by weight. The addition of silane coupling material affects the physical properties of the composite resulting in a decrease in water absorption by 33 % and a decrease in thickness swelling by 0.3 %. The inclusion of silane coupling agent led to an increase in tensile strength, tensile modulus, and flexural strength, while elongation decreased by 20 %. Thermal properties analysis showed that the silane treatment affected the decomposition of the composite material, reducing it by 2 % from 90 % without the coupling agent to 88 % with the coupling agent.

This article focuses on employment of nanotechnologies in remediation of tetracycline antibiotics (TC) from groundwater by green synthesized bimetallic Fe/Ni supported by limestone particles. An in-situ green synthesis nanoparticles was prepared using black tea leaves extract to generate a L-Fe/Ni nanocomposite. The synthesized nanocomposite was characterized using several techniques, such as, X-Ray Diffraction (XRD), Scanning Electron microscopy (SEM), transmission electron microscope (TEM), Energy dispersive X-ray (EDX), FTIR (Fourier Transform-Infra Red) spectroscopy and surface area. We then use response surface methodology (RSM) to optimize the synthesis process and evaluate the effectiveness of the prepared nanocomposite for tetracycline remediation. We took different simulated concentrations of the TC contaminant without relying on actual TC concentrations in grounwater, the best removal of the TC contaminant in batch study was investigated with relying on the initial concentrations of TC and other experimental factors such as pH, adsorbent nanomaterial concentration and time. A pilot plant was then constructed to eliminate the TC contaminant from groundwater in different concentrations, where the removal efficiency was found decreased with increasing in the concentration of the TC Many parameters affecting the removal mechanisms in statistical and continuous systems were examined to select the best results that accomplish the maximum elimination rate. With the improved operating conditions, (L-Fe/Ni concentration: 1500 mg/L; concentration of TC: 20 mg/L; pH: 7.2; contact time: 128 min), removal percent of TC was found 87 % based on RSM system. The L-Fe/Ni reactive medium of continuous column has a main role in slowing down the movement of the TC plume. This study showed that the ecofriendly nanocomposite could be an appropriate and novel method for remediation of antibiotics and other contaminants in groundwater.

Adsorption is a reliable and cost-effective technique for removing contaminants from wastewater. However, the major issue with the adsorption process is the regeneration and recovery of spent adsorbents. This review focuses on the Regeneration and recovery of pollutants from saturated adsorbent using acid (such as HCl, HNO₃, H₂SO₄ and organic acids), alkali (NaOH) or other chemicals (HNO₃, KCl, NaCl and NH₄Cl) (chemical regeneration), heat (thermal regeneration), micro-wave energy (microwave-assisted regeneration), electrical energy (electrochemical regeneration) and ultrasonic power (Ultrasound regeneration). The maximum desorption efficiencies observed were 99.5%, 92.6%, 284%, 150% and 66.61% in chemical, thermal, micro-wave-assisted, electrochemical and ultrasound regeneration techniques. The number of regeneration cycles performed was nearly in the range of 1-10 cycles. In the final step, waste is disposed of therefore incineration and landfill disposal have been discussed. However, among all these techniques, the Chemical regeneration technique has consumed the highest energy i.e. 6.6 kWh/kg.

The current challenges in the regeneration and recovery of saturated adsorbent such as operational cost, waste generation, development of eco-friendly technique, maintaining potential and efficiency of adsorbent and release of adsorbed pollutants, were also covered. Additionally, several aspects of the adsorption process such as applications of saturated adsorbents (antimicrobial agents or disinfectants, materials for civil construction, as a catalyst and fertilizers) were explained in detail. Mechanisms of adsorbents regeneration were also discussed in detail and emphasis has been drawn to the importance of adsorbent regeneration in the adsorption process. Therefore the novelty of this article is in overcoming the adsorption challenges and also focusing on metal recovery and adsorbent regeneration. Further studies should elucidate the techno-economic and environmental aspects.

Titanium dioxide (TiO₂) nanocrystals with dimensions below 100.0 nm exhibit a high crystal growth polymorphic behaviour in at least three distinct phases anatase, rutile and brookite. The phase composition and structural differences of these TiO₂ polymorphs profoundly influence their physicochemical properties, leading to variations in performance for various applications. Particular emphasis is placed on quantifying the structure-property relationships that govern the distinct behaviours of anatase (bandgap ∼3.20 eV), rutile (bandgap ∼3.0 eV) and brookite (bandgap ∼3.4 eV) nanocrystals which exhibit variations in photocatalytic activity. This review provides a comprehensive crystallographic analysis of the polymorphic phases of TiO₂ nanocrystals, focusing on their structural characteristics, phase transitions and stability. Crystalline TiO₂ phases show anatase (101), brookite (121) and rutile (110) diffraction and anatase and rutile are tetragonal, while brookite shows an orthorhombic structure. The review provides a systematic compilation of the phase biographs of TiO₂ polymorphs at the nanoscale through a detailed examination of X-ray diffraction patterns, electron microscopy images, and spectroscopic data. The effects of synthesis conditions such as temperature, precursors, and additives, on the phase composition and structural evolution are thoroughly discussed. Overall, this review provides a timely and comprehensive understanding of the crystallographic phase biographs of TiO₂ polymorphs at the nanoscale, paving the way for the rational design of high-performance TiO₂-based materials with tailored properties for diverse applications.

Applying soil electrokinetic remediation (SEKR) is considered a valuable technique to remediate contaminants-containing low permeability soils with the advantage of integration with other remediation approaches (e.g., chemical, physical, and biological). The basics and principles of electrokinetic remediation (EKR) were utilized in different fields of interest; for example, sedimentation, seed germination, consolidation, dewatering, etc. The present review is focused on the role of the electrode approaching/movement technique (EAMT) in improving the effectiveness of the SEKR. Based on our search in the collected literature, the influence of the EAMT on soil electrokinetic efficiency yielded no pertinent reviews. We looked for articles relevant to the EAMT in six search engines, and articles collected for the present review were chosen based on the data mentioned in the materials and methods section. Our objective was to illustrate the proper applicability of the EAMT from different perspectives to overcome some obstacles reported with the traditional SEKR. The effect of the EAMT is discussed/illustrated from four perspectives including a) the approaching/moving anode technique (AMAT), b) the approaching/moving cathode technique (AMCT), c) electrodes placement/gap, and d) continuously reoriented/rotating, reciprocating, and rotational electric fields. Several advantages could be gained from the EAMT application including a) improving the current passing, b) soil pH reduction, c) increasing heavy metals desorption, d) elevating the redox potential, e) reducing the energy consumption, f) increasing the removal percentages of contaminants, g) reducing extra chemical additives or pH modifications, h) enhancing electroosmotic flow, i) installing auxiliary electrodes presents a more stable current and uniform electric field, and j) ultimately reducing the environmental risks of heavy metals. Two methods were proposed for the practical applications of the EAMT (in-situ and ex-situ). Although there are various advantages were achieved from the application of the EMAT, the published research during the past 31 years (1993–2023) is few compared to other enhancement approaches.

Avocado (Persea americana) is a source of vegetable oil abundant in unsaturated fatty acids, vitamins, and diverse nutrients, rendering it a valuable source of functional oil. Refining is a necessary step to achieve avocado oil with high-quality attributes. This research delved into the impact of the refining procedure on some quality attributes of avocado oil obtained through screw pressing. The study encompassed four distinct samples, each corresponding to a specific stage in the refining process, i.e. degumming, neutralization, bleaching, and the crude oil as the control. Findings from the experiments revealed that the yield of avocado oils subjected to cooking pre-treatment (49.19±0.65 %) exceeded those without pre-treatment (45.10±1.71 %). Compared to crude oil, the quality of bleached oil was improved by reducing free fatty acid (52.94 %) and peroxide value (59.38 %). There were noticeable increases in free fatty acid and peroxide value during storage. The physicochemical properties of the extracted oil were affected by the stages of refinement and the duration of storage. FTIR analysis showed that the bleaching stage played a role in removing peroxides, hydroperoxides, and residual moisture. There were no significant changes in fatty acid composition during refinement. Oleic acid (52.0–53.1 %) constituted the largest proportion, trailed by palmitic acid (24.0–24.4 %), linoleic acid (17.2–17.8 %), and palmitoleic acid (4.9–5.6 %). However, unsaturated fatty acids content in avocado oil decreased significantly during storage.

This study evaluated the kinetic modeling of arabinoxylan (AX) extraction from Brewers’ spent grain (BSG) by alkaline pretreatment at atmospheric pressure, considering severe (low concentration of NaOH and high temperature) and moderate (high concentration of NaOH and low temperatures) process conditions. The effects of NaOH concentration and temperature on yield extraction were studied over time, as well as the concentration of weak acids and phenolic compounds at the end of the pre-treatment. The AX yield extraction varied from 41.2 % (1 M, 90°C) to 64.8 % (4 M, 40°C) after 1 h and 16 h, respectively. Acetic acid ranging from 420 ppm to 1020 ppm was released, while ferulic acid was the phenolic compound produced at the highest concentration ranging from 78.3 ppm to 224.1 ppm. In addition, rates of chemical reactions were correlated mathematically from the experimental data with a good fit, and a sensitivity analysis was performed to understand the kinetic behavior. The first-order kinetic model demonstrates that increasing AX extraction requires both low temperatures (between 30 and 40 °C) and low NaOH concentration, but at the same time, this effect increases the time required (16 h) to obtain the maximum AX yield (64.8 %).

The objective of the present investigation was to evaluate the parameters that affect the efficiency of electrocoagulation in a batch system to remove the azo-benzoic dye Red 40 present in synthetic wastewater by determining the effect of the operational parameters of voltage and treatment time. A 12×6 cm iron electrode holder was constructed with PVC pipes and screws separated by 2 cm, and a 1 L beaker was used as the electrocoagulation cell. Synthetic wastewater samples of red 40 were characterized, where UV–VIS was used to measure absorbance before and after being treated in the electrocoagulation cell. The effects of voltages (10, 15, and 20 V) and treatment times up to 60 min were evaluated. As a result, a higher removal of 93.85 % was obtained at 60 min when a voltage of 10 V was used with a lower change in temperature and energy consumption of only 14.08 kJ. The increase in conductivity and pH by values greater than 1600 µs/cm and 11, respectively, indicate the presence of diluted iron at the end of treatment; therefore, if complemented with other treatment methods such as filtration to remove excess iron produced, can be used in treatment plants and reduce their environmental impact, for this research the FTIR analysis showed that the sludge has a dye composition with hydroxides of metals along with a slight trace of dye degradation.