Leaching of silver (Ag) from electronic scrap by thiourea

Abstract

The leaching behavior of silver from electronic scrap using acidic thiourea solution was studied. The results showed that the silver leaching percentage was affected by the concentration of thiourea and hydrochloric acid, the oxidant such as ferric ions, solid-liquid ratio, temperature, rpm, etc. The leaching percentage of silver decreased with an increase in the solid-liquid ratio, and the leaching rate of silver was enhanced by increasing the thiourea and hydrochloric acid concentration. However, when the concentration of hydrochloric acid and oxidant were increased above 1.0 M and 30 mM, respectively, the leaching rate of silver decreased. When the reaction temperature was above 50 oC, the leaching rate of silver decreased because of the decomposition of thiourea. More than 99 % leaching of silver was achieved under the following conditions: thiourea conc. 0.8 M, HCl conc.: 0.5 M, Temp.: 35 oC, leaching time: 4 hours, solid-liquid ratio: 25 g/L.