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 The present study numerically investigates the removal of hydrogen sulfide (H₂S) from crude oil using natural gas as a stripping medium in a T-junction microchannel through three-dimensional computational fluid dynamics (CFD) simulations. The microchannel geometry was adapted from a previously reported experimental configuration and further optimized to reduce natural gas consumption and operating temperature. The Volume of Fluid (VOF) model coupled with the SIMPLE algorithm was implemented in ANSYS Fluent to simulate the gas–liquid two-phase flow and evaluate mass transfer characteristics. Simulations were conducted for gas flow rates of 200–1200 mL/min and oil temperatures in the range of 20–40 °C. The results showed that the H₂S removal efficiency increased with crude oil temperature and gas flow rate but decreased with higher oil flow rate. The predicted efficiencies ranged between 65.7% and 77.8%, in close agreement with experimental data (maximum relative error: 5.6%). The cold-stripping configuration achieved high desulfurization performance even at low gas temperatures (about 18 °C) while reducing gas consumption by nearly one-third compared with conventional units. This study proposes validated correlations and optimized operating parameters for efficient desulfurization of sour crude oil using a microchannel-based cold stripping process.

Abstract The optimization of membrane bioreactor (MBR) equipped with a submerged flat-sheet polyethersulfone (PES) membrane for the wastewater treatment from dairy processing facilities was investigated. The effects of key parameters such as the hydraulic retention time (HRT, from 8 to 16 hr), mixed liquor suspended solids (MLSS, 3000 to 9000
mg/L), and rate of aeration (Qair: 1 and 2 L/min) on COD removal efficiency were systematically investigated. Through the response surface method (RSM), the maximum the COD removal efficiency of 92.67% was obtained under the optimal conditions of HRT: 13.83 hr, MLSS: 7239.84 mg/L, and Qair: 1.75 L/min. The statistical analysis identified MLSS as the most influential factor in the COD removal efficiency, accounting for 30% of the variation, followed by HRT with
16%, and the rate of aeration showing the least impact of 8%. A notable reduction in the UV absorbance of wastewater between 200 and 500 nm, after treatment using MBR under optimal conditions, signified successful targeting of toxic or colored pollutants. Finally, a mechanism for the wastewater treatment in MBRs, which included the biological degradation, adsorption on the surface of biomass and membrane, and separation through membrane filtration, was proposed.

Abstract In this research, the methods of oxidation, oxidation along with carbon nanotubes and surface absorption of carbon nanotubes were investigated to remove the drug substance of cefixime from aqueous solutions. In these methods, the removal percentage of cefixime was 78%, 96% and 70% respectively. Therefore, the results showed that oxidation with carbon nanotubes had a positive effect on the removal of cefixime. For this reason, oxidation along with carbon nanotubes was used to remove the cefixime. Next, different operating parameters such as the concentration of drug pollutants (20,30,40 and 55ppm), reaction time (5,10,15,20,25 and 30 min), concentration of hydrogen peroxide (1, 3 and 5ml) and amount of carbon nanotubes (0.05, 0.01 and 0.2 g/l) were studied in the removal process of cefixime using the method of  oxidation along with carbon nanotubes. It should be noted that in all experiments, certain amounts of carbon nanotubes and the oxidizing agent of hydrogen peroxide were used. In addition, a mixer, with a given round, was used to mix the materials. The maximum removal efficiency of cefixime from aqueous solutions is about 96% , which is related to the process of the removal of cefixime at the constant concentration of 55 mg/L by 0.1 g/L of carbon nanotubes and 5ml of hydrogen peroxide at the  t = 30 min.

Abstract In the present study, Choline hydroxide (ChOH) as an ionic liquid catalyst was used for transesterification of soybean oil into biodiesel in a microchannel reactor. The effects of three variables i.e. reaction temperature, catalyst dosage and total flow rate on fatty acid methyl ester (FAME) content (wt. %) were optimized using Box–Behnken experimental design. In order to predict the FAME content a quadratic polynomial model was obtained. The optimal conditions from the model were reaction temperature of 53.53 °C, catalyst dosage of 2.6 wt. % and total flow rate of 11.82 mL/min. At these conditions, the predicted FAME content was 96.45 wt.% and the experimental FAME content was obtained 97.6 wt. %. The proximity of the experimental results and predicted values showed that the regression model issignificant. Using the ionic liquid catalyst in the studied microreactor for transesterification leads to diminish the reaction time to the order of seconds compared to conventional batch systems. In addition, the reusability of ChOH catalyst was investigated. The results revealed that the catalyst had perfect utility after several runs without much loss in the activity.