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 nickel (II) ion removal from aqueous solutions using Fe₃O₄ nanoparticles was investigated. The influence of adsorbent dosage, contact time, and pH on removal efficiency was examined and optimized using response surface methodology (RSM). The maximum removal efficiency achieved with the ultrasonic-assisted process was 84.3% at 60 minutes of contact time, 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 include 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 a temperature of 77 °C, a sulfuric acid concentration of 1.75 M, a leaching duration of 4 hours, and a 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 were conducted, which demonstrated a specific capacity of 350 mAh/g. This capacity is comparable to that of 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 PES NF/TiO₂/AO was fabricated. The morphology of the final membrane was investigated using FESEM, EDX and FTIR analysis. Membrane separation performance was evaluated through contact angle measurement, 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 that can be attributed to the surface modification of the initial membrane. The removal efficiencies for heavy metals Pb and Cu using the pristine membrane were measured at 28.2% and 43%, respectively, while the optimized membrane showed 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 voltage, feed composition, and operation time. Among the fabricated membranes, M3 (8 wt% MWCNTs) exhibited the best performance, providing optimal ionic conductivity, selectivity, and structural stability. Maximum chemical yield was achieved when solute concentrations in the electrode chambers exceeded those in the desalination chamber. In contrast, M4 (10 wt% MWCNTs) showed reduced efficiency, attributed to MWCNTs agglomeration and pore blockage that hindered ion transport. Increasing voltage improved ion transport up to an 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 MWCNTs loading optimization and controlled operating conditions. Overall, PVC/MWCNTs composite IEMs exhibited significant potential for integrated chemical production and saline wastewater treatment, 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 alkyl chain length 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 gradual alkyl chain elongation 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 alkyl chain length weakens electrostatic interactions and enhances free volume, leading to a systematic reduction in density and cohesive energy density. Structural analysis reveals well-defined cation–anion coordination shells, reflecting strong local ionic organization across all systems. Dynamical analysis shows a consistent decrease in ionic mobility with chain elongation due to stronger van der Waals interactions and steric effects, which in turn reduces diffusion and ionic conductivity. Importantly, 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 with increasing alkyl chain length.

Abstract This study presents the premier report of gold nanoparticle (AuNP) synthesis using Teucrium polium (T. polium) plant extract, investigating the antimicrobial activity of both aqueous and methanolic T. polium extracts and the synthesized AuNPs. Additionally, the effect of different concentrations of synthesized AuNPs on the phytochemical properties of T. polium plant extract was examined. The results of Ultraviolet-visible spectroscopy (UV-Vis spectroscopy), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FTIR) tests on AuNPs confirmed their synthesis. SEM and TEM images showed that the AuNPs were spherical in shape with an average size of 22.89 nm. The surface plasmon resonance (SPR) peak of the UV-Vis spectroscopy corresponding to the synthesized AuNPs appeared at 420 nm. The optimal pH of the reaction solution was also equal to 5. According to the results, the methanolic extract exhibited significantly higher antibacterial and antifungal activity compared to the aqueous extract, with the maximum inhibition zone diameters observed for Escherichia coli (14±1.4 mm) and Aspergillus Niger (15±0.7 mm). Moreover, the antimicrobial activity of AuNPs showed that these nanoparticles have relatively good ability to inhibit gram-negative bacteria, with the largest inhibition zone diameters observed for Escherichia coli (18±0.7 mm) and Aspergillus niger (20±0.9 mm). The antioxidant and reducing power activity (phenolic flavonoids content) of T. polium plant extract treated with different concentrations of synthesized AuNPs increased with increasing nanoparticle concentrations up to 60 ppm (IC50=9.94 µg/mL and reducing power= 16.85 mMFe²⁺/mg sample), and decreased at higher concentrations.