Separation Technology,
N. Mostafazadeh; A.A. Ghoreyshi; K. Pirzadeh
Volume 15, Issue 4 , November 2018, , Pages 27-47
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 ...
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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.
Separation Technology,
M. Yasemi; M. Rahimi; A. Heydarinasab; M. Ardjmand
Volume 15, Issue 3 , September 2018, , Pages 15-33
Abstract
In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence ...
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In this study, extraction of tannic acid using microchannel was investigated. Affective parameters were optimized. Different solvents including buthanol, ethylacetate and n-hexane as organic phase, methanol, propanol, ethanol and water as aqueous phase investigated. Microchannels with different confluence angles and diameters were examined. Microchannels with different confluence angles and diameters were examined. The effects of pH, temperature, and volumetric flow ratio and contact time of the two phases were investigated. The response surface methodology was used to optimize extraction yield of tannin from Quercus leaves in the employed microchannels. Based on this optimization, maximum yield was achieved at pH=2, temperature=33.1℃, volumetric flow ratio =1.2 and contact time of 25.35s. Results show that extraction-using microchannel has many advantages over traditional methods, including shorter time and higher economic efficiency. Moreover, microchannel provides smaller volume of fluids resulting in lower solvent consumption, lower waste production, shorter analytical times, smaller space requirements, and lower energy consumption.