Recovery of indium from used indium–tin oxide (ITO) targets

A novel hydrometallurgical process was developed for the recovery of indium metal from used indium and tin oxide (ITO) targets, which includes acid leaching, removing tin from leach solution by sulphide precipitation and depositing sponge indium by zinc cementation. The leaching of indium reached 99% with ITO powder size of less than 75 um and initial acid concentration of 100 g/L H2SO4 at L/S ratio of 8–12 and 90 °C for 2 h, while only about 8% of tin was leached out. Tin in the leach solution was reduced to 10 mg/L and the loss of indium was less than 1% by sulphide precipitation under H2S partial pressure of 101.3 KPa and 100 g/L H2SO4 at 60 °C for 10 min. Pure sponge indium from purified In2(SO4)3 solution was obtained using zinc plate cementation at pH 1–1.5 and 65 °C.

Research Highlights
► Sulphide precipitation was employed to resolve the separation of Sn from indium. The results showed that the Sn in the solution was reduced to 1.35 mg/L with initial acidity of 100 g H2SO4/L, 50g/L of In3+ and 5g/L of Sn2+, while only 0.47% of In lost.
► This paper investigates a novel process to recover indium from used ITO targets, including acid leaching- sulphide precipitation-zinc cementation. The results showed that the recovery of indium reached 99% in each step. The high indium recovery was able to ensure great economic value and practical applicability.