Extraction of Indium from Leaching Residue of Roasted Zinc Sulphide Concentrate

Zinc sulfide concentrate which is produced from Irankoh mine ore, contains indium. In this study, recovery conditions of indium from leaching residue of roasted zinc sulfide concentrate were investigated. Indium concentration in leaching residue of zinc sulfide concentrate was 145ppm. Optimum values of effective parameters were as follows: initial concentration of sulfuric acid solution of 100 g/L, temperature of 90°C, leaching time of 3 hours and the amount of required sodium sulfide for iron reduction 1.5 iron stoichiometric ratios. Then, indium was selectively precipitated from the leach solution. For selective indium precipitation, the pH of leaching solution was adjusted to six using ammonia in 90°C, and indium precipitation time was considered to be 10 minutes. Concentration of indium in resulting precipitation was 2650ppm. Finally, the resulting precipitation was dissolved using hot sulfuric acid solution, and the solution was subject to solvent extraction and cementation using zinc powder to recover indium. Total recovery of indium from zinc leaching residue was obtained more than 92% and product purity was more than 94.5%.