South African Journal of Chemical Engineering最新文献

In this work, the corrosion inhibition performance of polyethyleneglycol bisphenol A epichlorohydrin copolymer (PEG-BEC) against mild steel in 1 M HCl was studied by electrochemical and weight loss techniques. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDAX) were applied to characterize the surface morphology of the mild steel samples. The corrosion mitigation efficiency was observed to rise as the concentration of PEG-BEC rises in the corrosive medium while increasing the temperature (25 °C -65 °C) resulting in a drop in the inhibition ability. Furthermore, under hydrodynamic conditions, the corrosion of the mild steel was found to deteriorate both in the absence and presence of PEG-BEC. Just with 10 ppm, an inhibition efficiency (IE) of 97.6% was obtained at 25 °C by EIS. PEG-BEC acts as a mixed-type inhibitor as observed by potentiodynamic polarization (PDP) technique. The observed corrosion inhibition action of PEG-BEC could be ascribed to the adsorption of the molecules and the formation of a protective film on the steel surface as evidenced by static water contact angle (WCA). Langmuir isotherm best describes the PEC-BEG-metal adsorption with large K_ads values indicating a thermodynamically stable nature inhibition process. The obtained ∆G°_ads = -35.138 to -39.522 kJ/mol indicate that the PEG-BEC spontaneously adsorbed onto the steel with strong tendency to provide protection to the mild steel surface via combination of chemisorption and physisorption processes. The ΔH_ads -53.07 kJ/mol and ΔS_ads= +0.048 kJ/mol-k, respectively, suggests an exothermic reaction accompanied by relatively increase in entropy of the PEG-BEC adsorption on the mild steel surface.

Cubic equations of state are utilized to model the behavior of substances in both liquid and gaseous states, incorporating cubic order terms in their variables. These equations are pivotal in describing the behavior of real substances, particularly their deviations from ideal behavior. Furthermore, they facilitate the prediction of a range of thermodynamic properties, including pressure, volume, temperature, and compressibility factors. This study was conducted with the objective of evaluating the compressibility factor using four distinct cubic equations of state: Van der Waals, Redlich–Kwong, Soave-Redlich–KwongRedlich–Kwong, and Peng–Robinson. The analysis focused on the dependency of these equations on temperature, pressure, and component fractions in binary mixtures. A numerical algorithm, featuring algebraic solutions, was developed on the Excel platform to enable graphical analysis of the mixtures in question. The results of this analysis led to the establishment of a parametric relationship for the compressibility factor, dependent on temperature, pressure, and concentration.

The study's findings reveal significant discrepancies in the compressibility factors calculated using the Van der Waals (VDW) equation compared to those from the Redlich–Kwong (R–KR–K) and Peng–Robinson (P–R) equations, with deviations reaching as high as 16.13 %. Specifically, at the maximum pressure investigated, the compressibility factor derived from the VDW equation (1.519) significantly differed from that obtained via the Soave-Redlich–Kwong (S-R–K) equation (1.222), showing a 0.297 difference, or 19.55 %. This disparity is attributed to how temperature affects the repulsive forces term in the S-R–K, P–R, and R–K equations, leading to a closer approximation of the compressibility factor profile. Additionally, the P–R and S-R–K cubic state equations account for the acentric factor, a crucial parameter that influences compressibility factor behavior by considering the molecular size involved in the process. In conclusion, the Soave-Redlich–Kwong cubic equation of state was found to align most closely with experimental data and was therefore selected to explore the compressibility factor's behavior in relation to pressure across various fractions and temperatures within the examined systems.

Molecular docking (Mol.Doc) approach of an azo-ester based fluorophore (AEF) with widely studied proteins like Human serum Albumin (HSA), Bovine serum Albumin (BSA), Beta lactoglobin (βLG) and Ovalbumin (OVA) were carried out. The binding affinity and strength of AEF-HSA complex is due to hydrogen-bonding (h-bonding) and hydrophobic interactions (predominantly attributed to pi-alkyl). AEF and HSA acts as h-bonding acceptor as well as donor. The energetically favored conformers of AEF-HSA complex are governed and stabilized by polar as well as non-polar amino acids. On the contrary, the pattern observed in all the conformers of AEF-BSA, AEF- βLG and AEF-OVA are energetically least favored (+ve ∆G) compared to that of HSA. The least binding affinity of AEF is towards OVA (Binding energy (BE) +581.15 Kcalmol⁻¹ followed by βLG (+55.11) and BSA (+12.12) . Though BSA and HSA are structurally similar to each other, they vary in the binding stability with AEF. This is attributed to several unfavorable interactions that destabilize AEF-BSA complex which was not resulted in the complex existing between AEF-HSA. The energetically least stable complexes (AEF-BSA, AEF-βLG and AEF-OVA) are predominantly governed by hydrophobic interactions. However, several h-bonding interactions along with pi-sigma/pi-pi/pi-alkyl interactions result in destabilization of the above complexes. Interestingly, AEF-HSA complex stability is attributed to fewer number of hydrophobic interactions along with h-bonding interactions. The h-bonding interaction governs the stability of the complex which is the driving force. Docking studies illustrates that the binding of amino acids (AAs) in various subdomains play a significant role on the binding nature. The stability of AEF-HSA over other protein complexes in terms of BE is emphasized in the study. The energetically stable sites and sub-domains of AEF with HSA and BSA establish the site selective and site-specific nature of AEF with proteins. In silico studies provide an excellent and easier approach in establishing the molecular interactions existing between AEF with globular proteins. ADMET parameters of the guest molecule calculated exemplifies that AEF compound is less toxic and possesses high oral bioavailability. Based on the binding efficiency of AEF with albumins, the ADMET properties and drug likeliness approach of AEF provides an information on the application towards proteins in the concept of medicine and chemistry.

The primary goal of this research outline is the conversion of titanium isopropoxide (TTIP) at 50.0 °C to form a high crystalline preferred oriented predominant (101) with a low crystal strain of 90.0 % anatase-TiO₂ phase. With the interval of time, the peptizing agent (IP) reacts to an acidic aqueous medium and preferential growth of anatase-TiO₂ has been identified. Exhaustive recombination in X-ray diffraction (XRD) analysis ensures the crystal strain, lattice volume, lattice parameters, d-spacing and crystallite size. UV–vis-NIR showed maximum absorption of 320.0 nm with 0.78 a.u. at blue shift for decreasing nano-size and smaller bandgap 3.0313 eV of larger dimensions anatase-TiO₂. The preferred orientation also revealed by nanobeam diffraction (NBD) of TEM enables qualitative lattice type and highly crystal orientated predominant (101) plane 5.60 nm⁻¹ in a diffraction pattern imposed on 200.0 kv parallel electron bean from LaB₆ filament.

The heat transfer by natural convection of a nanofluid, which is ethylene glycol$-A{l}_2{O}_3$ has been analyzed in an open cavity numerically using the multiple-relaxation-time - lattice Boltzmann method by the graphics processing unit high-performance parallel computing. The right side of the cavity is open, and different boundary conditions have been applied to all the walls. Besides, one adiabatic fin has been installed on each side of the enclosure’s top and bottom sides. Here, the Prandtl number is fixed at 16.6, and the Rayleigh number changes from ${10}^4-{10}^6$ with the nanoparticle volume fraction from $0\%-5\%$ has been used for numerical simulations. Besides, in this work, the power-law index is an important parameter as well, and 0.7, 0.8, 1, 1.2, and 1.4 are the values of this parameter. Results are presented concerning both the average and local Nusselt numbers in the form of streamlines, isotherms, temperature distributions, velocity distributions, heat transfer rate, and entropy production. It is observed when increases, average Nusselt number increases $607.94\%$, and for this reason, the overall heat transfer rate rises because of buoyancy force. In addition, the average Nusselt number falls by $83.28\%$ when the power-law index rises; as a result, the total heat transfer rate falls because fluid viscosity increases with the power-law index. It is also observed that for shear-thickening fluids, the temperature gradient is higher. On the contrary, the temperature started decreasing with the increase of the power-law index. Additionally, the local Nusselt number value rises as power-law index falls. Moreover, the heat transfer rate increases by $7.08\%$ when volume fraction increases. The intensity of buoyancy force reduces with the increase of volume fraction. Besides, the overall entropy generation rises when the Rayleigh number and the volume fraction increase, but it decreases when the power-law index increases. So, when the Rayleigh number is ${10}^6$, the power-law index is 0.7, and the volume fraction is 0.00 then the entropy generation is the highest. This current research has many applications for example heat exchangers, electronic cooling equipment, solar heating systems, aerospace applications, medical devices, and entropy generation-related systems.

This study delves into the impact of aging on PVDF membranes due to exposure to various NaOCl-based household bleach products, namely Bayclin, Proclin, and Soclin, over different durations (0, 1, 3, and 5 days). The primary objective is to assess the influence of household bleaches as cleaning agents on the stability and durability of PVDF membranes. Our findings underscore that prolonged exposure to NaOCl-based cleaning agents induces changes in pore structure, morphology, mechanical strength, and flux performance of the membranes owing to oxidation by hypochlorite. However, these alterations are mitigated when using household cleaning agents, particularly Soclin and Proclin. For instance, after 5 days, membranes aged with NaOCl exhibited an enlargement of pore size up to 0.2 mm, whereas those aged with Soclin (MS) and Proclin (MP) only experienced an enlargement to 0.12 mm from the original pore size of 0.05 mm. This increase in pore size is undesirable as it adversely affects the selectivity performance of the membranes. Additionally, the hydrophilicity of membranes was found to be better maintained when aged with household products compared to pure NaOCl, as evidenced by the higher water contact angle observed in MP and MS membranes. Furthermore, the flux recovery ratio (FRR) exhibited an upward trend with prolonged aging duration, with Bayclin showing the highest FRR of 180 %, closely to that of pure NaOCl at nearly 190 %, among the other two products. This significant increase in FRR is undesirable as it results from the enlargement of pore morphology caused by damage from exposure to hypochlorites which is stronger in the chemical-grade NaOCl compared to the household bleach products. In summary, this study highlights that household bleaches, especially Soclin and Proclin, present a promising option in terms of stability for prolonged use. These results are crucial for identifying chemicals that are not only more efficient in the cleaning process but also less damaging to the membranes with good stability in long-term use.

In the current trend of industrial manufacturing processes, an interest in utilization of industrial and agricultural wastes for producing green chemistry, eco-friendly product, has been increased. Therefore, this study aimed to produce ethyl lactate using solid-acid catalyst WO₃/zeolite-A via esterification. Various analytical techniques, including XRF, BET, XPS, FTIR, NH₃-IR, NH₃-TPD, SEM-EDX, ICP-OES, XRD, TGA-DTA, and TEM, were employed to analyze the physical and chemical properties of zeolite-A and tungsten-supported on zeolite-A. The results revealed that after five reuse cycles, the lactic acid conversion rates were 20.1 % and 10.3 % for WO₃/zeolite-A and Amberlyst-15, respectively. The spent WO₃/zeolite-A exhibited a reduction in surface acid site, declining from 1,591.8 μmol/g in the first run to 690.1 μmol/g in the fifth run. The decline in efficiency was attributed to impurities blocking of active sites, structural alterations, and partial leaching of active species. XRD and FTIR analyses confirmed decreased crystallinity and structural changes in spent catalysts. TEM, SEM-EDS, and ICP-OES analyses showed the loss of active tungsten species and the deposition of reaction intermediates leading to a decrease in ethyl lactate yield (decreased from ca. 44 to 20 %). Despite structural changes affecting catalytic performance, WO₃/zeolite-A demonstrated a good promising catalyst for ethyl lactate production over five successive cycles (with ca. 50 % decrease).

The study used ANN-GA and RSM to predict the best process parameters for generating epoxide from Azadirachta indica seed oil (AISO). This procedure used carbonized sulphonated melon seed peel catalyst. FTIR, SEM, XRD, BET, and XRF measurements confirm the -SO₃H group's attachment to the solid catalyst. The dependant variable was relative conversion to oxirane (RCO), while the independent parameters were catalyst dosage (0.6, 1.2, 1.8 wt %), time (4, 6, 8 h), and temperature (50°C, 60°C, 70°C). The ANN was evaluated using 11 backpropagation (BP) methods. Each method was examined with three input layer neurons for catalyst dosage, duration, and temperature. Ten neurons were in the hidden layer and one was in the output layer signifying RCO. The AISO epoxidation process forecast was most accurate using Bayesian regularisation. Simulated RSM and ANN models were built using experimental and algorithmic designs. The 3D plots showed that process parameters significantly affected RCO. R² and MSE were used to evaluate model performance. For process forecasting, the ANN model (R²=0.9999, MSE=2.3404E-13) outperforms the RSM model (R²=0.9979, MSE=0.4688). Under the best RSM circumstances, RCO yield was 78.03 %. Additionally, the ANN and ANN-GA yielded 85.84 % and 92.51 %, respectively at optimal conditions of 0.6 wt % catalyst, 50°C temperature, and 6 h reaction time. However, all techniques optimized AISO and matched experimental results (RCO-77.41 %). FT-IR and GCMS characterizations of epoxy AISO corroborated the oxirane ring's attachment. The results show that ANN-GA is a reliable method for modelling and optimizing AISO epoxide production utilizing CSMSPC, encouraging sustainable development.

This study investigates the reactivity kinetics of biochar from biomass. The biochars were obtained by pyrolyzing peanut shells (PNS_800), cashew nut shells (CNS_800), and millet stalks (MS_800) at 800 °C in a fixed bed reactor. The chemical composition of the biochar samples shows that silicon (Si), potassium (K), and magnesium (Mg) are the major elements in the biochar of peanut shells (PNS_800) while potassium and magnesium are the major elements in the biochar of cashew nut shells (CNS_800) and millet stalks (MS_800). The biochars were activated in a CO₂ (200 Nml/min) atmosphere at temperatures 1123 K, 1173 K, and 1223 K under atmospheric pressure. The random pore model (RPM) and a modified random pore model (MRPM) were used to correlate the reactivity profiles versus carbon conversion and to determine the kinetic parameters. It was observed that biochar reactivity increases as the temperature increases, attaining at least three times at 1173 K than those corresponding to 1123 K. Furthermore, the increase in reactivity is more pronounced with the biochar MS_800. It was observed that the RPM model cannot follow the kinetic of the experimental reactivity of all biochar samples. However, a better fitting of the reactivity is obtained when using the MRPM model. The activation energies (E_a) are distributed in the range of 98.11–148.46 kJ/mol while the pre-exponential factors (k₀) are in the range of 19.31–249.53 s^-1. It was observed that for the MRPM model, the lower activation energy and the lower pre-exponential factor were obtained by the biochar CNS_800. However, E_a et k₀ are well evaluated for PNS_800 and MS_800 with a coefficient of determination of 99.76%. The proposed modified random pore model could be used to describe the reactivity of biochar from biomass as well as the reactivity of coal.

The combination of iron and copper (Fe/Cu) loaded on glass (G-Fe/Cu) has been developed for this study. The green synthesis was used to create bimetallic nanoparticles (G-Fe/Cu) using grape leaves extract, which employed as a natural reducing agent to easily produce nZVI from iron salts. The particle size, surface morphology, elemental composition and degree of crystallinity of the resulting nanocomposite have been analyzed by means of energy-dispersive X-ray spectroscopy (EDX), scanning electronic microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). G-Fe/Cu nanocomposite were employed as adsorbent materials to eliminate ciprofloxacin (CIP) from polluted aqueous solution. Some factors affecting the adsorption function, in batch and continuous experimentations have been examined to select the optimum parameters that accomplish the maximum elimination ratio (99 %) and to investigate the efficiency of the nanoparticles as reactive bed materials. It was discovered that the ideal conditions were CIP concentration (50 ppm), pH 7, nanoparticles dosage (0.5 mg/ 50 mL) and 100 min of optimum contact time. In present paper, the response surface methodology (RSM) was applied as statistical tool used to optimize and model complex systems for elimination of CIP antibiotic from aqueous solution with selection the same four factors that mentioned above. The best appropriate isotherm model was the Freundlich model in batch study. The findings imply that hazardous compounds can be successfully eliminated from aqueous solutions using the prepared nanocomposites. The model's predictions aligned well with experimental outcomes, and the G-Fe/Cu nanocomposite effectively removed CIP from the solutions.