Asia-Pacific Journal of Chemical Engineering最新文献

The aim of the current study is to investigate the CO₂ adsorption on the mesoporous silica. The adsorbent was characterized by XRD, TEM, SEM, and N2 adsorption desorption. The adsorption isotherms of carbon dioxide (CO₂) on the silica were investigated using a static volumetric method at various temperatures. The response surface methodology (RSM) was applied to the influence of different variables and their interaction on the response (CO₂ adsorption capacity) in order to obtain the optimal conditions. According to the analysis of variance, the pressure and the temperature parameters are the variables that influence the CO₂ adsorption capacity. Freundlich, Langmuir, and Langmuir–Freundlich (L-F) models were used to depict the isothermal data, and the L-F model exhibited the best correlation with the experimental isotherm. In addition, the temperature-dependent L-F model was applied to adjust the CO₂ adsorption data on the adsorbent, and the isosteric heat of CO₂ was calculated. Additionally, compared with other samples, the mesoporous silica demonstrated superior regenerability and thermal stability.

With the increasing global energy demand and the growing prominence of environmental issues, biodiesel has garnered significant attention as a renewable, low-emission green energy source. Conventional hydrotalcite-based catalysts often suffer from insufficient basicity and limited accessibility of active sites, leading to relatively long reaction times and limited efficiency. This study synthesizes Mg-Al hydrotalcites composed of various metal salts via the co-precipitation method and employs them as supports for K₂CO₃ to efficiently produce biodiesel. The transesterification performance of different Mg-Al hydrotalcite catalysts was evaluated using a three-component reaction (rapeseed oil, methanol, and methyl acetate) under conditions of an oil-ester-alcohol ratio of 1:1:10, a catalyst loading of 10 wt%, and a reaction temperature of 60°C. Results indicated that Mg-Al hydrotalcite derived from acetate metal salts using K₂CO₃ as the precipitant achieved a high biodiesel yield of 98.79% within 15 min, which is substantially faster than most reported hydrotalcite-based reactions that typically require 30–120 min under comparable conditions. TG-DTA analysis revealed that the formation of potassium aluminum oxide after high-temperature calcination, which provides more alkaline sites as suggested by CO₂-TPD profiles, is a key reason for the high catalytic activity. BET and SEM analyses showed that the catalysts possess a large specific surface area and rich pore structure, significantly enhancing the dispersion of alkaline sites. These synergistic features enable ultrafast biodiesel synthesis and provide a promising strategy for designing efficient and sustainable solid base catalysts for large-scale biofuel production.

This study analyzes the influence of Arrhenius activation energy on the chemically reactive, magnetohydrodynamic Casson hybrid nanofluid flow past an exponentially stretching surface embedded in a Darcy–Forchheimer porous medium with a non-uniform heat source/sink. The governing nonlinear partial differential equations, formulated under the Rosseland approximation for radiative heat flux, were reduced to coupled ordinary differential equations using similarity transformations. These equations were solved numerically via the fourth-order Runge–Kutta method with a shooting algorithm. Validation against existing benchmark results showed excellent agreement. Furthermore, the streamline patterns for mono, nano, and hybrid nanofluids are presented to analyze flow. Casson fluid properties, stimulated by yield stress, alter the velocity and temperature fields due to internal resistance. The non-uniform heat sources and porosity variation raise thermal energy input and flow spatial heterogeneity resistance, leading to complex thermal boundary interaction. Arrhenius activation energy does not affect the fluid temperature but meaningfully boosts the chemical reaction rate by enhancing the species concentration gradient. The hybridized nanofluid composition augments thermal conductivity as a result of free nanoparticles' collision, which inspires heat transfer performance. These findings hold significant assurance for practical applications in sustainability and energy efficiency, leading to the development of environmental benefits and reduced energy costs. These findings demonstrate that hybrid nanofluid composition and nonlinear rheological effects can be tuned to optimize heat and mass transfer in bio-convective systems, catalytic porous reactors, and solar thermal applications.

The persistent environmental threat from dye-contaminated industrial wastewater necessitates advanced remediation solutions. Hydrochloric acid–modified activated alumina spheres (HAAs) are presented as efficient adsorbents for anionic dye removal. Comprehensive characterization (SEM, XRD, BET, FTIR, Zeta potential, NH₃-TPD) confirmed the effects of acid treatment. The treatment enhanced crystallinity, amplified surface charge positivity, and enriched acid site density. These synergistic modifications endowed HAAs with exceptional orange II adsorption capacity (97.91% removal within 40 min at 50 ppm, pH 8). Its performance outperformed pristine activated alumina. Multimodal adsorption mechanisms were identified: 1) electrostatic attraction via sustained positive charge, 2) hydrogen bonding through hydroxyl groups, 3) Lewis acid–base coordination at enhanced acid sites, and 4) mesopore confinement. The process followed pseudo-second-order kinetics and Temkin isotherm confirming chemisorption-dominated heterogeneous interactions. Notably, HAAs exhibited robust reusability and cost-effectiveness, with facile solid–liquid separation advantages. Theoretical analysis suggests HAA demonstrates promising scalability and engineering adaptability for potential industrial dye wastewater treatment applications. This approach could potentially bridge laboratory-scale innovations with practical environmental remediation scenarios, although actual implementation would require further validation.

The utilisation of viscoelastic Walter's B nanoliquid in engineering and biomedical applications gained substantial attention because of its ability to provide real-time fluid behaviour, particularly in the heat flow mechanism. In particular, the flow of viscoelastic fluid over an elongating surface is useful in polymer processing and biomedical flows. The integration of dissipative heat combined with radiant heat and melting heat transfer in these models shows enhanced control over thermal gradients, chemical reaction species, etc. Moreover, the insertion of homogenous and heterogeneous chemical reactions augments the applicability of simulating catalysed surface reactions, which control the release of the drug. Further, the impact of Brownian motion combined with thermophoresis portrays a significant characteristic in enhancing the fluid properties. The increased governing parameters lead to nonlinearity, and coupled effects of melting are highly sensitive; therefore, the model is handled numerically employing a shooting-based Runge–Kutta technique. The assumptions involved in various systems are analysed graphically following the validation of the result in a particular case.

In the process of railway coal transportation, a large amount of coal dust is dispersed, causing serious economic loss and environmental pollution. In order to improve the low-temperature dust suppression performance, the present study has developed an antifreeze-type, high-efficiency railway coal transportation dust suppressant (hereinafter referred to as dust suppressant). The principle utilizes electrostatic attraction between the carboxylate ions (CMC⁻) of polymer and the Ca²⁺ ions of the antifreeze agent, coupling the hydrogen bonding between hydroxyl, ether, amide, and other functional groups to improve the low-temperature cross-linking between macromolecular chains of sodium carboxymethylcellulose (CMC-Na) and polypropylene amide (PAM), and meanwhile weakening the connections between water molecules as well as water molecule and macromolecular substances, so as to avoid the low-temperature freezing of water molecules and achieve the low-temperature rapid consolidation of polymer molecules at the same time. The optimal ratio of the dust suppressant solution obtained in this study was 0.4% CMC-Na, 22% calcium chloride (CaCl₂), 0.03% PAM, and 77.57% water. It was proven that this dust suppressant solution has good antifreezing and solidifying properties and can achieve efficient dust suppression in railway coal transportation. The present study can fill in the blanks of the existing low-temperature dust suppression technology, and the proposed mechanism can further enrich the existing dust suppression theory.

This study examined the degradation of Reactive Red 180 and safranin using zinc oxide photocatalysis. Complete dye removal was achieved for both dyes under optimal conditions within 2 h. For Reactive Red 180, the optimum conditions were pH 10, 0.5 g/L zinc oxide, 25 ppm dye concentration, and 1 L volume. For safranin, the conditions were pH 10, 0.75 g/L ZnO, 25 ppm dye concentration, and 1 L volume. In terms of reusability, the removal efficiency of Reactive Red 180 decreased from 100% at the 1st cycle to 82% after five cycles, while safranin removal remained constant across all cycles. A comparison between photocatalysis and photo-membrane systems was conducted on real textile wastewater with an original pH of 10.45 and a Pt/Co value of 1000 ppm. In the Photocatalytic Membrane Reactor, 100% dye removal and 48% chemical oxygen demand removal were achieved in 2 h using a zinc oxide amount of 0.75 g/L. In the photocatalytic system, 86% dye removal efficiency and 20% chemical oxygen demand removal efficiency were achieved after 4 h. The photocatalytic membrane reactor presents an efficient, durable, and cost-effective solution for various industrial and environmental processes, making it a promising alternative to traditional photocatalytic systems.

The hybrid nanofluid integrated with micropolar fluid shows growing interest due to the enhanced thermal performance in microscale devices. These improved properties are due to their greater thermal conductivity and rotational effects. The proposed study assesses the significance of velocity slip on the flow characteristic of micropolar nanofluids via an expanding/contracting surface immersed in a permeable medium under the action of Darcy–Forchheimer inertial drag. In particular, the integration of magnetite nanoparticles $�{\mathrm{Fe}}_3�O_4$ and $�{\mathrm{TiO}}_2$ in the traditional liquid, ethylene glycol, is utilized for the enhanced thermal transport features of the hybrid nanofluid. The proposed assumptions have several applications in the cooling of microelectromechanical systems, porous media filtration and so forth. The model formulated for the proposed assumptions is obtained and designed in the form of non-linear coupled equations. Further, suitable transformation rules are adopted in transforming these equations into dimensional form, and shooting combined with Runge–Kutta fourth-order is utilized for the solution. Moreover, the important outcomes obtained from the physical description of several factors affecting the flow phenomena are that the concentration of magnetized nanoparticles effectively controls the momentum distribution, where the radiating heat, characterized by thermal radiation, upsurges the heat transport phenomenon.

This study presents a comparative evaluation of phosphate adsorption on pristine ZIF-8 and Fe₃O₄-doped ZIF-8 (Fe₃O₄/ZIF-8), a hybrid adsorbent combining high surface area with magnetic separability. Structural integrity and composition were confirmed using SEM, XRD, FTIR, and XPS. Comparative studies on phosphate removal by Fe₃O₄/ZIF-8 are scarce, and this work provides a direct evaluation against pristine ZIF-8 under identical conditions. ZIF-8 exhibited a higher maximum adsorption capacity (521 mg/g equivalent to 170 mg P/g at 50°C) but slower adsorption rates (k₁ = 0.0852–0.1303 min⁻¹). In contrast, Fe₃O₄/ZIF-8 showed a lower capacity (187 mg/g, 61 mg P/g, at 50°C) but faster kinetics (k₁ = 0.1513–0.2533 min⁻¹), along with improved selectivity in the presence of competing anions, and superior reusability, retaining ~60% efficiency after 4 cycles versus ~33% for ZIF-8. Adsorption followed the pseudo-second-order and Sips models, and both materials were effective at acidic to neutral pH. These findings demonstrate that Fe₃O₄ incorporation does not necessarily increase adsorption capacity but provides operational advantages such as magnetic retrievability, faster adsorption, and greater regeneration stability. The comparative perspective offers valuable insight into the rational design of multifunctional MOF-based adsorbents, positioning Fe₃O₄/ZIF-8 as a promising candidate for sustainable phosphate removal in complex water environments.

In this study, marble waste (MARWAS) beneficiation was done using thermal, physical, and chemical means. The MARWAS samples collected from dumping yards of Kishangarh and Revdar districts of Rajasthan (India) and Ambaji district of Gujarat (India) were characterized by chemical composition analysis, scanning electron microscopy with energy-dispersive spectroscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). These were then subjected to different beneficiation schemes: (1) calcination followed by slaking and clarification, (2) cationic reverse floatation, and (3) acidulation followed by magnetic separation. These aim to enhance the calcite content by removing siliceous and ferrous impurities. The percentage removal of impurities (PRIs) of these schemes was calculated using chemical composition analysis of purified products. The acid dissolution method (PRI = 93.97%) was more efficient for eliminating siliceous than the reverse floatation method (PRI = 68–73%), while the magnetic separation (PRI = 99.32%) completely removed the ferrous impurities. Although the PRI is just about 45% in the calcination method, it is useful for decomposing the material to eliminate the impurities strongly entangled between the calcite matrix. Purified products (CaO, Ca (OH)₂, and CaCl₂) obtained by these beneficiation schemes can be used to synthesize high-grade CaCO₃ powder to serve as a feed supplement in poultry, filler in papermaking, and in toothpaste, etc.