Indium

The extraction process of indium mainly relies on the extraction-electrolysis method, which is also the mainstream process technology for indium production in the world today. The principle process flow is as follows: indium-containing raw materials → enrichment → chemical dissolution → purification → extraction → reverse extraction → zinc (aluminum) displacement → sponge indium → electrolytic refining → refined indium.

Ninety percent of the world's indium production comes from by-products of lead-zinc smelters. The main method for the smelting and recovery of indium is to recover it through enrichment from the smelting slag, molten slag and anode slime of copper, lead and zinc. Depending on the source of the recycled raw materials and the difference in indium content, different extraction processes are applied to achieve the best configuration and maximum benefit. Commonly used process technologies include oxidation slagging, metal displacement, electrolytic enrichment, acid leaching extraction, extractive electrolysis, ion exchange, and electrolytic refining, etc. At present, the solvent extraction method is widely used, which is an efficient separation and extraction process. The ion exchange method for the recovery of indium has not yet been reported to be industrialized. During the process of separating indium from the less volatile tin and copper, most of the indium is concentrated in the flue ash and scum. When separated from volatile zinc and cadmium, indium is enriched in the slag and filter residue.