EXTRACTION AND RECOVERY OF SILVER IONS FROM PHARMACEUTICAL PROCESSES VIA HOLLOW FIBER SUPPORTED LIQUID MEMBRANE

Abstract

This work studied the extraction and recovery of silver ions via hollow fiber supported liquid membrane (HFSLM). Pharmaceutical wastewater containing silver ions of 30 mg/L was used as a feed solution. Type of organic solvents was selected by considering its solubility. Kerosene was found to be the suitable organic solvent. For an extractant and a stripping solution, respectively, LIX 84-I and sodium thiosulfate solution were selected by liquid-liquid extraction. The maximum percentages of extraction and recovery of silver ions via the HFSLM were 98% and 85%, respectively by following conditions: pH of feed and stripping solutions at 3.5 and 2 respectively, the concentration of extractant and stripping solutions 0.1 and 0.5 mol/L, equal flow rate of feed and stripping solutions 200 mL/min, and separation time of 26 min. The operating mode in HFSLM was applied by countercurrent-circulating of feed and stripping solutions. The residual concentration of silver ions in the feed solution less than 1 mg/L was observed. The effect of ferric ions was additionally studied and found no influence on silver ion extraction. In addition, the mathematical models considering the convection, diffusion, chemical reaction and the accumulation of silver ion complexes in the liquid membrane phase were developed in order to understand mass transfer of silver ions throughout the HFSLM as well as to predict the extraction and recovery of silver ions and the separation time. The models showed high accuracy as the calculated results from the models were deviated from the experimental data less than 2%.