... extraction, in this a compound which is a good ligand for copper is dissolved in a solvent which is immiscible with water (doesn't mix). It is then mixed with the solution containing the Cu2+ ions the ligand then binds with the Cu ions as below. Cu2+ (aq) + 2LH (organic) CuL2 (organic) + 2H+ (aq) This process can then be reversed by mixing the organic solution with a small amount of concentrated acid. This pushes the Cu2+ ions into the solution containing the acid gaining a further increase in the concentration of Cu2+ ions. Both of these processes depend on the pH. The leftover solution then goes to an open pond where t. ferro-oxidans catalyses oxidation of the remaining Fe2+ ions to Fe3+ ions. This recharges the solution, which is then pumped back to the top of the waste pile to start the process again. The separated copper is then collected ...

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