Iranian Journal of Chemical Engineering (IJChE)

Abstract In this study, ZIF-67 was synthesized through solvothermal method to remove Cr(VI) ions from aqueous solution. To improve the structural properties of ZIF-67 and its adsorption capacity, optimization of the synthesis conditions was carried out based on maximum Cr(VI) uptake. From experiments, the optimum condition was revealed as solvent: metal ion molar ratio of 4.6:1, ligand: metal ion molar ratio of 318:1 and temperature of 23℃. The physio-chemical properties of as-synthesized ZIF-67 were investigated by BET, XRD, FTIR and FESEM analyses. Effect of adsorption pH, adsorbent dosage, initial concentration and contact time on adsorption process was investigated. Based on the results, the maximum adsorption capacity of Cr(VI) was 26.27 mg/g which was obtained at 35℃, pH= 5, adsorbent dosage of 3 g/l and initial concentration of 107.82 mg/l. The equilibrium time for Cr(VI) adsorption varied from 180 min for low initial concentration of 9 mg/L to 240 min for a high initial concentration of 90 mg/L. For the synthesized ZIF-67, maximum uptake capacity was reported 26.27 mg/g at initial concentration of 107.82 mg/l. The equilibrium data were described better by Langmuir-Freundlich isotherm model than the other models at three different temperatures. Pseudo-second-order model fitted the experimental data better than pseudo-first-order one. Adsorption thermodynamics indicated that the adsorption process was endothermic and spontaneous in nature. The regenerability of ZIF-67 was also studied in three sequential cycles and the Cr(VI) adsorption was almost retained after two cycles.

Abstract The present study investigates the potential applicability of the extracted pectin from sour orange pomace as adsorbent for Ni (II) removal from aqueous solution. Pectin extraction from the pomace was carried out using HCl and the highest pectin extraction yield of 26.75% was obtained. The Fourier transform infrared (FTIR) spectroscopy analysis confirmed that the structure of the extracted pectin was similar to the commercial one. The morphology and chemical characteristics of pectin beads were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX) techniques. The influence of several parameters including pH, initial metal concentration, adsorption temperature and time was studied to optimize nickel removal. The maximum Ni (II) removal of 85.1% was obtained at initial concentration of 20 mg/L and the highest adsorption capacity of 19.76 mg/g was achieved at nickel concentration of 100 mg/L. Kinetic and equilibrium studies were done to evaluate Ni (II) sorption from aqueous solution by the synthesized beads. Results showed that the sorption process follows a pseudo- second- order kinetic model. The equilibrium data were well correlated with Langmuir and Redlich-Peterson models by high regression coefficients.

Abstract In this study, polysulfone (PSF) flat membrane prepared via non-solvent phase inversion method was employed in gas-liquid membrane contactor module to absorb CO2. Two polymer concentrations of 16 wt% and 18 wt% were used in the dope solution of fabricated membranes. The membranes were characterized in terms of morphological structure and contact angle. Scanning electron microscopy (SEM) analysis demonstrated that PSF membrane with polymer concentration of 16 wt% in the dope solution has a porous layer with a combination of finger-like, sponge-like and macrovoid structures, but the other membrane has a sponge-like structure. Also, characterization results through atomic force microscopy (AFM) and contact angle measurement demonstrated that the porosity, surface roughness and hydrophobicity of the PSF membranes decreased with an increase in polymer concentration. Evaluationof mass transfer resistance displayed that the resistance of the PSF membrane with polymer concentration of 18wt% in the dope solution is higher than that of the other membrane. In addition, decreasing the polymer concentration significantly improved CO2 absorption flux. At the absorbent flow rate of 9.7 ml/min, the CO 2 absorption flux of PSF membrane with 16 wt% polymer concentration was 2.17 times higher than the absorption flux of the PSF with 18 wt% polymer concentration.

Abstract Chlorinated hydrocarbons and aromatics are the major volatile organic compounds that contaminate the ground water and industrial waste waters. The best way to overcome this problem is to recover the dissolved compounds in water. In order to evaluate the potential ability of granular activated carbon (GAC) for recovery of volatile organic compounds from water, the equilibrium adsorption was investigated. This study deals with the adsorption of dichloromethane as a typical chlorinated volatile organic compound (VOCs) and toluene as the representative of aromatic volatile organic compounds on a commercial GAC. The adsorption isotherms of these two volatile organic compounds on GAC were measured at three different temperatures, toluene at 293, 303 and 313 K and dichloromethane at 298, 303 and 313 K within their solubility concentration range in water. The maximum adsorption capacity of dichloromethane and toluene adsorption by GAC was 4 and 0.2 mol/Kg-1, respectively. The experimental data obtained were correlated with different adsorption isotherm models. The Langmuir model was well adapted to the description of dichloromethane adsorption on GAC at all three temperatures, while the adsorption of toluene on GAC was found to be well described by the Langmuir-BET hybrid model at all three temperatures. The heat of adsorption was also calculated based on the thermodynamic equation of Clausius–Clapeyron, which indicates the adsorption process is endothermic for both compounds.