Silver extraction using emulsion liquid membrane system containing D2EHPA-TBP as synergistic carrier: optimization...

The present investigation deals with silver extraction using an emulsion liquid membrane. The emulsion liquid membrane system consists of paraffin as organic phase, Span 80 as surfactant, Di-(2-ethylhexyl) phosphoric acid (D2EHPA) and Tributyl Phosphate (TBP) as carrier, and hydrochloric acid as stripping agent. Experiments were designed and modeled by response surface methodology using Design Expert 11 software, which determines the extraction rate as a function of Span 80 concentration, D2EHPA concentration, TBP concentration, HCl concentration, and treatment ratio. The ANOVA results indicate that the model is statistically significant because of the high R² (0.9828) and the low p-value of <0.0001. The results showed that the silver extraction increases by increasing all affecting parameters up to their optimal values and after that extraction rate decreases with increasing of them. The process was optimized to obtain maximum extraction rate, minimum D2EHPA concentration, and minimum treatment ratio. The optimal conditions were obtained at a surfactant concentration 3.26% (V/V), D2EHPA concentration 0.0045 mol/L, TBP concentration 5% (V/V), HCl concentration 0.56 mol/L, and treatment ratio 0.5. Under these conditions, the silver extraction rate was 99.87%.