Abstract:In the process of recovering indium from the post-reduction leaching solution during hydrometallurgical refining of zinc, part of tin enters the stripping solution, which affects the quality of subsequent refined indium. Due to the impurities such as indium and tin in the tin removal residue, tin will be gradually enriched in the system, as to affect the service life of extractant and reduce the production efficiency. In this paper, the removal of tin in the solution after stripping was studied by using the pre-adjustment of pH value-H2O2 oxidation method. Condition tests were made on endpoint pH value, amount of hydrogen peroxide added, reaction duration, etc. to investigate the tin removal effects under different conditions, and exploration was made on tin removal from tin removal residue by means of acid leaching and alkali leaching. The results show that the separation of indium and tin can be achieved by controlling the temperature of indium stripping solution at 50℃, endpoint pH at about 2.0, reaction time at 1h, amount of hydrogen peroxide added at 5g/L and the hydrogen peroxide being added in a low speed. Using concentrated sulfuric acid or concentrated hydrochloric acid to leach tin removal residue can not meet the requirements of indium leaching, and part of tin is leached into the solution during the process, which cannot realize the complete separation of indium and tin. If alkaline leaching approach is adopted, when the reaction temperature is controlled at 90℃, the liquid to solid ratio at 3∶1, the reaction duration at 2h and amount of sodium hydroxide added at 100g/L or more, 80% of tin can be separated from tin removal residue and enters the solution, and indium is basically not react with sodium hydroxide and remains in slag, thus realizing the complete separation of indium and tin.
