Iranian Journal of Chemical Engineering (IJChE)

Abstract Heavy metals are among the most hazardous pollutants released into the environment through industrial activities. In recent years, adsorption has been recognized as an effective method for the removal of metal ions from wastewater. Ultrasonic irradiation is a promising technique for intensifying mass transfer during adsorption. In this study, the effect of high-frequency ultrasonic waves on the enhancement of the removal of nickel (II) ion from aqueous solutions using Fe₃O₄ nanoparticles was investigated. The influence of the dosage of adsorbenst, contact time, and pH on the removal efficiency was examined to optimize the removal efficiency using the response surface methodology (RSM). The maximum removal efficiency, achieved with the ultrasound-assisted process, was 84.3% at the contact time of 60 minutes, 8 g of Fe₃O₄, and pH = 5, while the conventional stirring (shaker) method resulted in a maximum efficiency of 79.54% at 100 minutes, 10 g of adsorbent, and pH = 9. The use of ultrasound significantly accelerated the adsorption rate at the initial stages by generating cavitation and microstreaming, which increased the availability of active surface sites on the nanoparticles. These findings demonstrate that the combination of Fe₃O₄ nanoparticles and ultrasonic irradiation offers a rapid, efficient, and environmentally friendly approach for the removal of nickel (II) ions from industrial wastewater.

Abstract Lithium-ion batteries are widely used in various electronic devices and typically discarded after their service life, causing significant environmental damage and resource wastage. Therefore, recycling the valuable components of the batteries, such as graphite, is essential. Graphite, employed as the anode material, is one of the key components targeted for recovery. In graphite recycling operations from spent batteries, critical hydrometallurgical processes are primary and secondary leaching stages using sulfuric acid. In this research, both leaching processes were systematically optimized. The optimal conditions identified for primary leaching were the temperature of 77 °C, concentration of 1.75 M of sulfuric acid, leaching duration of 4 hours, and liquid-to-solid graphite powder ratio of 5. Under these conditions, the graphite purity after the primary leaching process was 99.56 wt%. Subsequently, in the secondary leaching stage, a final high purity of 99.98% was achieved for the graphite product. To evaluate the electrochemical performance of the recycled graphite, galvanostatic charge-discharge tests, which demonstrated the specific capacity of 350 mAh/g, were conducted. This capacity is comparable to that of the commercial graphite, confirming the effectiveness of the developed recycling process.

Abstract In this study, Nano filtration (NF) membranes, composed of polyethersulfone (PES) modified with titanium dioxide (TiO₂) nanoparticles, were fabricated using the phase inversion method. By grafting aniline oligomers onto the surface of the modified membrane, the final membrane with the structure of PES NF/TiO₂/AO was fabricated. The morphology of the final membrane was investigated using FESEM, EDX and FTIR analyses. The membrane separation performance was evaluated through measuring the contact angle and pure water flux (PWF), flux recovery ratio (FRR%), and salt rejection tests using Na₂SO₄ and MgSO₄ solutions. The highest PWF (3.66 kg/(m^2.h)) was obtained with the final modified membrane compared to the initial membrane at an operating pressure of 4.5 bar, which can be attributed to the increased hydrophilicity caused by the surface modification of the initial membrane. The removal efficiencies for heavy metals Pb and Cu using the pristine membrane were measured to be 28.2% and 43%, respectively, while the optimized membrane showed the significantly improved rejection rates of 99.97% and 94%. Furthermore, the total fouling rate of the original membrane was approximately 70.4%, which was reduced to 47.4% in the modified membrane. The irreversible fouling was reduced from 44.5% in the original membrane to 32.6% in the optimized membrane, indicating an improvement in the antifouling performance of the modified membrane. The results suggest that the PES NF/TiO₂/AO modified membrane can be considered an effective approach for enhancing the physical and chemical properties of membranes, as well as their separation performance, particularly for the removal of heavy metals.

Abstract This study investigates the performance of an electrodialysis metathesis (EDM) process using polyvinyl chloride/carbon nanotube (PVC/MWCNTs) nanocomposite ion-exchange membranes (IEMs) for simultaneous water desalination and chemical production. IEMs, with MWCNTs loadings of 0% (M1), 4% (M2), 8% (M3), and 10% (M4) by weight, were fabricated and characterized for water sorption, areal electrical resistance, hydrophobicity, and mechanical strength. Their ion selectivity, separation performance, desalination efficiency, and production yield were systematically evaluated under varying applied voltages, feed compositions, and operation times. Among the fabricated membranes, M3 (8 wt% MWCNTs) exhibited the best performance, providing optimal ionic conductivity, selectivity, and structural stability. The maximum chemical yield was achieved when the solute concentrations in the electrode chambers exceeded those in the desalination chamber. In contrast, M4 (10 wt% MWCNTs) showed reduced efficiency, attributed to the agglomeration of MWCNTs and pore blockage that hindered ion transport. Increasing voltage improved ion transport to the optimal level, but excessive voltage (15 V) caused water splitting and concentration polarization, lowering both chemical yield and desalination efficiency. These results highlight the importance of optimizing MWCNT loading and controlled operating conditions. Overall, PVC/MWCNT composite IEMs exhibited significant potential for integrated chemical production and the treatment of saline wastewater, providing a cost-effective and scalable strategy for resource recovery.

Abstract This study employs classical molecular dynamics simulations using the OPLS-AA force field to systematically investigate the influence of the length of alkyl chain on the structural, thermodynamic, and dynamical properties of a homologous series of pyridinium-based ionic liquids (methyl- to pentyl-pyridinium bromide). The main objective is to elucidate how the gradual elongation of the alkyl chain affects intermolecular interactions and ion transport behavior at the molecular level. The model demonstrates good agreement with available experimental density data, confirming its reliability for predicting physicochemical trends in these systems. The results indicate that increasing the length of the alkyl chain weakens electrostatic interactions and enhances free volume, leading to a systematic reduction in density and cohesive energy density. The structural analysis reveals well-defined cation–anion coordination shells, reflecting strong local ionic organization across all systems. The dynamical analysis shows a consistent decrease in the ionic mobility with the elongationof chains, due to stronger van der Waals interactions and steric effects, which in turn reduce diffusion and ionic conductivity. Importantly, the ionic transference numbers calculated from ion mobilities clearly demonstrate that cations contribute more to charge transport than anions in all investigated systems. This cation-dominated transport behavior provides a direct molecular-level explanation for the observed decrease in ionic conductivity by increasing the length of chains.

Abstract In this research, gold nanoparticles (AuNPs) were synthesized for the first time utilizing the extract of Teucrium polium. The study evaluated the antimicrobial potential of both methanolic and aqueous extracts of T. polium, alongside the synthesized AuNPs. Furthermore, the impact of varying AuNP concentrations on the phytochemical characteristics of the plant extract was analyzed. The successful fabrication of AuNPs was verified through a comprehensive suite of characterization techniques, including UV-Vis spectroscopy, XRD, TEM, SEM, and FTIR. Morphological analysis via SEM and TEM revealed spherical nanoparticles with a mean diameter of 22.89 nm, while the UV-Vis spectrum exhibited a characteristic surface plasmon resonance (SPR) peak at 420 nm. The reaction reached its optimum efficiency at pH 5. Antimicrobial assays indicated that the methanolic extract possessed superior antibacterial and antifungal properties compared to the aqueous version, yielding maximum inhibition zones for Escherichia coli (14±1.4 mm) and Aspergillus niger (15±0.7 mm). Additionally, the AuNPs demonstrated notable efficacy against gram-negative bacteria, with the highest inhibition observed for E. coli (18±0.7 mm) and A. niger (20±0.9 mm). Regarding the antioxidant capacity and reducing power (phenolic flavonoid content), a concentration-dependent increase was observed up to 60 ppm (IC50=9.94 µg/mL; reducing power= 16.85 mMFe2+/mg sample), followed by a decline at concentrations exceeding this threshold.