Two-step Leaching of Valuable Metals in Waste Printed Circuit Boards

The two-step leaching was studied torecover the valuable metals in waste printed circuit boards(PCBs).Firstly,sulfuric acid with hydrogen peroxide was used to leach the base metal;andsecondly,the aqua regiato leach gold in the base metal.The optimal base metal leaching conditions were as follows;hydrogen peroxide of 20 mL;solid-liquid ratio of 1:5;sulfuric acid concentration of 5 mol/L;reaction temperature of 60 ℃ and reaction time of 90 min.Thedissolution ratio of raw material(10 g) reached90.0%under the above conditions.The gold leaching efficiency reached 97.5%at 40 ℃ with reaction time of 30 min.Studies have shown that the two-step leaching can effectively deal with PCBs,and the gold dissolution process is controlled by diffusion.