Reductive Leaching Kinetics of Indium and Further Selective Separation by Fraction Precipitation

Reductive leaching of high-iron bearing zinc leaching residue (HIZLR) by zinc sulfide concentrate to extract indium and its further selective separation from the leachate were studied. The results indicated that over 95% of indium extraction was achieved at particle sizes of 74−105 μm, reaction temperature of 90 °C, leaching time of 300 min and sulfuric acid concentration of 1.4 mol/L. The leaching kinetics was analyzed by the shrinking core model, and the leaching data from various experimental conditions indicated that the reactions were controlled by the diffusion through the solid product layer with an activation energy of 17.96 kJ/mol. The order of the reaction with respect to the sulfuric acid concentration was determined to be 2.41. Over 99% of copper and arsenic were coprecipitated in the cementation of copper with iron powder. More than 98% of indium was selectively separated from zinc sulfate solution with high ferrous ion content, and the indium-rich precipitate, which had an indium content of approximately 2.4%, could be further treated by the acid leaching−solvent extraction−electrowinning process to produce pure indium.