Optimization of synergistic green emulsion liquid membrane stability for enhancement of silver recovery from aqueous solution

Abstract

The emulsion liquid membrane (ELM) process for silver recovery containing synergistic Cyanex 302/Cyanex 272 carriers, palm oil as a diluent, acidic thiourea as a stripping agent, and sorbitan monooleate (Span 80) as a surfactant was attempted. A suitable range of mixed carrier concentration on the facilitated extraction performance of silver was first determined. Response surface methodology (RSM) was applied to optimize and evaluate the effect of mixed carrier concentration, stripping agent concentration, and treat ratio on the stability of the process. The results showed that the system was stable with no breakage or swelling. At the optimum condition of 8.26/12.39 mM Cyanex 302/Cyanex 272, 1.27 M acidic thiourea, and 0.62 treat ratio, the silver extraction performance and recovery were 97% and 54% (4.33 times enrichment), respectively. Further modification of the process and addition of 5% w/v of modifier resulted in 6.57 times enrichment, which accounted for 82% of the silver recovery. Hence, this study shows the capability of silver recovery using a synergistic ELM process and potential to be applied in industrial effluent.