Non-toxic, high selectivity process for the extraction of precious metals from waste printed circuit boards

Abstract The work presented here focused on the extraction of gold (Au), silver (Ag) and palladium (Pd) from electronic waste using a solution ammonium thiosulfate. Thiosulfate was used as valid alternative to cyanide for precious metal extractions, due its non-toxicity high selectivity. interactions between sodium thiosulfate, total ammonia/ammonium, concentrations particle size printed circuit boards (WPCBs) were studied by response surface methodology (RSM) principal component analysis (PCA) maximize mobilization. Au reached efficiency with granulometry less than 0.25 mm, but consumption reagents high. On other hand, Ag depended neither thiosulfate/ammonia concentration nor WPCBs it showed 90% also biggest (0.50 < Ø 1.00 mm). Pd extraction, similarly Au, best smallest medium WPCB sizes, required compared Au. results that leaching is complex process (mainly which requires more severe conditions in order achieve efficiencies) correlated reagent concentrations, sizes. These have great potentiality, suggesting possibility selective recovery metals based different WPCBs. Furthermore, efficiencies obtained all bode well perspective large-scale applications.