Recovering indium with sulfating roasting from copper-smelting ash

A technology for recovering indium from Jinchuan copper-smelting ash was developed. Indium in the ash was first enriched to the leaching-slag in leaching process, and then recovered by sulfating roasting. The method included mixing the leaching-slag with sulfuric acid, making them into particles, roasting the mixture, and then leaching the calcine with hot water. Above 90% of indium in calcine could be dissolved into the leaching solution. The optimized conditions were determined as follows: the mass ratio of sulfuric acid to leaching slag was 0.1, the roasting time was about 1 to 1.5 h in the temperature range of 200-250°C, and the calcine was leached for 1 h with 5:1 of liquid/solid ratio at 60°C. Over 99% of indium in leaching solution was finally enriched by Zn substitution or sulfide precipitation.