Recovery of Silver from Dilute Effluents via Electrodeposition and Redox Replacement

Abstract

In this study, the electrodeposition-redox replacement (EDRR) method was studied for the recovery of minor concentrations of silver from dilute solutions. The parameter optimization was carried out with synthetic solutions similar to silver oxide button battery recycling effluents, consisting of sulfuric acid and concentrated base metal (10 g·L−1 H2SO4, 60 g/L Zn2+) with a minor amount of silver (100 ppm) and a varying amount of Fe3+ ions. Results of these experiments were analyzed both electrochemically and by use of SEM-EDS. The role of dissolved Fe3+ ions was studied by varying the concentration from 0 to 1000 ppm and the results showed that although the presence of Fe ions decreased silver recovery efficiency, final product purity was found to increase slightly. The EDRR process was also found to be more effective for Ag recovery and has less energy consumption when Fe3+ concentrations are relatively low (≤ 100 ppm) when compared with conventional direct current electrowinning. In the final stage, silver was successfully recovered via EDRR, using the optimized conditions, from a real pregnant leaching solution (PLS) obtained from the leaching of silver oxide batteries.