Removal of tin and extraction of indium from acid-dissolved solution of waste indium-tin targets

Abstract

The recovery of indium from waste indium tin oxide (ITO) target has great significance for the economy and environment. Based on our previous study on the optimization of acid leaching technique, the present study focuses on tin removal via zinc substitution and indium recovery from a tin-free leach solution. The results show that when the amount of added zinc powder and reaction time increase, the tin removal effect can be improved. The optimal conditions obtained are as follows: additional content of zinc powder from 20 g/L to 25 g/L, reaction temperature of 60 °C, and reaction time from 3 h to 4 h. Under this condition, the tin removal rate exceeds 98%, and the tin content in the tin removal solution is lower than 0.05 g/L. After tin removal, the substitution time could be reduced from 3–5 d to 1–2 d by neutralizing the residual acid by using alkaline residue and maintaining the pH value less than 2. The indium recovery rate is also improved when this condition is used. The indium content in the tin residue is reduced to lower than 0.1% and the acid-insoluble β-SnO₂ could be obtained via the strong nitric acid leaching of the indium-containing tin residue. Indium could be recovered from ITO with a high purity of 99.995% via electrorefining.

Keywords

tin removal / leaching / ITO waste targets / recovery rate

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