3. Leaching

Leaching involves dissolving the desired metals in ionic forms. The aim is to determine the optimum type of leachates in terms of reagent consumption and cost, minimum solubilization of impurities and equipment maintenance. The leaching process involves the following stages (figure  2 ):

• the reagent diffuses from the solution to the surface of the material, where it adsorbs ;

• the chemical reaction taking place on the surface of the material leads to the formation of a soluble species ;

• the reaction product desorbs from the surface...