Electrochemical Behavior of Tin and Silver during the Electrorecycling of Pb-free Solder (Sn-Ag-Cu) Waste

Abstract

We investigated the electrochemical behavior of Sn (93.0 %)-Ag (4.06 %)-Cu (0.89 %) during electrolysis of Pb-free solder waste to recover tin and silver. A thin strip of the solder waste produced by high-temperature melting and casting was used as a working electrode to perform electrochemical analysis. During anodic polarization, the current peak of an active region decreased with an increase in the concentration of sulfuric acid used as an electrolyte. This resulted in the electro-dissolution of the working electrode in the electrolyte (1.0 molL -1 sulfuric acid) for a constant current study. The study revealed that the thickening of an anode slime layer at the working surface continuously increased the electrode potential of the working electrode. At 10 mAcm -2 , the dissolution reaction continued for 25 h. By contrast, at 50 mAcm -2 , a sharp increase in the electrode potential stopped the dissolution in 2.5 h. During dissolution, silver enrichment in the anode slime reached 94.3% in the 1 molL -1 sulfuric acid electrolyte containing a 0.3 molL -1 chlorine ion, which was 12.7% higher than that without chlorine