Copper can be extracted from low-grade ore (CuFeS2) by means of bacterial leaching.

Authors Avatar

        Copper can be extracted from low-grade ore (CuFeS2) by means of bacterial leaching. The low-grade ore and tailings are put onto an area of impermeable ground. This is then covered in an acidic leeching solution that contains the bacteria, T. ferro-oxidans and T. thio-oxidans. These bacteria are best suited to an acidic environment. All the bacteria need are Fe2+ ions or S2- ions, oxygen, carbon dioxide and bacterial nutrients containing phosphorus and nitrogen.  The final result is that the bacteria convert the insoluble chalcopyrite into a solution containing Cu2+, Fe2+, Fe3+ and SO2- ions. The solution carrying the copper ions can be straightforwardly drained off as it is on an impermeable base layer. The Cu2+ is removed from the solution by ligand exchange solvent extraction.  This is where the ligand, a compound with a lone pair of electrons, binds to metal ions. A complex is then formed with the metal ion in the centre surrounded by the lignads. The Fe2+ and Fe3+ ions are left behind in the aqueous solution. A compound that is a good ligand for copper ions is dissolved in an organic solvent immiscible in water, such as kerosene. When this solution is mixed with the copper ions dissolved in water, this reaction takes place:

Cu2+(aq) + 2LH (organic)  CuL2 (organic) + 2H+(aq)

Join now!

L = Ligand

This process moves the copper ions from the water, where they are at a low concentration, to the organic solvent, where they are at a high concentration. After the copper ions have been removed the remaining Fe2+ ions and Fe3+ ions are oxidised in an open pond with the T. ferro-oxidans catalysing this reaction. The recharged leeching solution is then pumped back to the beginning of the cycle to be used again.

The copper is extracted as sheets through an electro-winning process. An electric current is passed through the copper ion solution. The copper ions are oxidised ...

This is a preview of the whole essay