Leaching of copper sulphide mineral
About 80% of copper is produced through pyrometallurgical process.Hydrometallurgical techniques for the recovery of copper are used mostly for copper oxide and chalcocite ores but these processes will be used for the recovery of copper from sulphide ores because they offer acceptable environmental effects The most economical solvent for the copper oxide minerals are sulphuric acid. But sulphuric acid cannot leach the sulphide minerals easily.
In the last 30 years many research has been investigated which are related to the leaching of sulfide minerals in chloride media specially with FeCl3 .Recent researches indicated that leaching with ferric chloride is more effective than ferric sulphate but one of the most important problems is the conversion of chloride solution to sulphate solution in order to electrowinning process.
Sulfuric acid has usually less effect on copper sulphide mineral and can leach it according the following reactions:
MeS + 2 H+ = Me2+ +H2S Absent of oxidizing agent
MeS + 2 H+ + 0.5 O2 = Me2+ + S + H2O Present of oxidizing agent
H2S + 0.5 O2 = S + H2O (S + 1.5 O2 + H2O = H2SO4)
Fe2 (SO4)3 solution can leach the copper sulphide minerals according the following reactions :
Cu2S +Fe2 (SO4)3= CuSO4 + 2FeSO4 + CuS
CuS + Fe2 (SO4)3= CuSO4 + 2FeSO4 + S
CuFeS2 + 2Fe2(SO4)3 = CuSO4 + 5FeSO4 + 2S
It seems that Bioleaching is now the only leaching method, which is used for sulphide mineral ores or concentrates. But it hopes via research in the future to find new process for this purpose.