4. Purification and production of the (semi)-finished product

Leaching is rarely selective. The solution contains impurities that can interfere with the production of the desired metal or impair its purity. It is therefore necessary either to purify the solution resulting from the leaching step, in a purification step, or to selectively extract the metal species of interest, leaving the impurities in solution, in a selective extraction step. During this stage, the metal species can be extracted in turn in order to separate them and produce a pure metal salt, by precipitation for example. The techniques used to extract, separate or purify are usually the same as those used to produce the semi-finished or finished product. In this section, we present the main unit operations used to extract, separate, purify and process the (semi)-finished product, with no particular distinction.