Application of response surface methodology for the extraction and enrichment of silver from aqueous solutions by emulsion liquid membrane

Silver is a toxic and carcinogenic pollutant and must be removed from industrial effluents. In the present investigation response surface methodology (RSM) is used to optimize the process parameters for the extraction and enrichment of silver from aqueous solutions using emulsion liquid membrane technique. The liquid membrane used was composed of liquid paraffin as the solvent, sorbitan monooleate (SPAN-80) as the surfactant , hydrochloric acid as the internal reagent and Bis (2-ethylhexyl) phosphoric acid (D2EHPA )as the carrier. The process parameters namely, surfactant concentration, carrier concentration, pH and treat ratio of membrane to external feed phase on the extraction and enrichment of silver were optimized using Box–Behnken design. The results show that the optimal values for surfactant concentration , carrier concentration , pH and treat ratio of the system were 3.24%v/v, 0.05 molar, 6.89, and 0.230.23, respectively . At the optimized conditions the maximum silver extraction was 96% and enrichment was 10.3%.