Integrated emulsion liquid membrane process for enhanced silver recovery from copper-silver leached solution

Abstract

Waste printed circuit boards (WPCBs) have become the major source of e-waste and offer the prospect of being a secondary resource. In this work, copper (Cu) and silver (Ag) from WPCBs leached solution were treated using the integrated emulsion liquid membrane (IELM) process. Almost complete Cu (39660 mg/L) and Ag (300 mg/L) were treated using the precipitation and ELM process, respectively. The Cu was removed and recovered as CuO nanoparticles using hydroxide precipitation at pH=8.34. Subsequently, the Cu-free WPCBs leached solution loaded with Ag was treated using the ELM process. The best optimum formulation for the stable ELM process was accomplished at 7.74 mM of Cyanex 302, 70.0 mM thiourea/2.5 mM HNO₃ and 1 % w/v of Span 80 as a carrier, synergistic stripping agent, and surfactant, respectively. For high recovery of Ag, the optimum condition was obtained at a treat ratio of 1:3.243 with 200 rpm agitation speed at 4.36 minutes of extraction time. Under these conditions, more than 95 % and 80 % of Ag were successfully extracted and recovered, respectively with an enrichment ratio of 5.2. Hence, it is of great significance that this IELM process is proposed for the treatment of WPCBs leached solution.