VITO and KULeuven develop new process for the recovery of copper from chrysocolla

Copper silicate chrysocolla (CuSiO3·2H2O) contains approximately 34 wt% of copper and is a common mineral to be found together with malachite and azurite in oxidized copper deposits. Despite of its large potential as a copper resource, difficulties in beneficiation (e.g. poor floatability) and metallurgical processing (e.g. formation of silica gel during acid leaching) limit the utilization of chrysocolla. However, there are solutions to these challenges.  

Scanning electron microscopy combined with energy dispersive x-ray (SEM-EDX) analysis indicated the presence of copper-depleted silica surface layers in residual copper-containing chunks that eventually hinders complete copper extraction. However, it was demonstrated that either milling the leach residue to create fresh accessible surfaces or milling the starting material into finer particle size could improve copper extraction yield. Fourier-transform infrared (FTIR) analysis suggests that the leaching mechanism occurs via coordination of the amine functional group of MEA to copper(II) ions. The addition of ammonium chloride to MEA is expected to have provided chloride counter anions that kept the formed copper-ammine complex in solution.

Copper was recovered from the pregnant leach solution by sulfide precipitation with an aqueous (NH4)2S solution. Copper was precipitated as a covellite phase, with more than 98 % recovery yield. Furthermore, the reusability of the lixiviant was demonstrated by four leaching-precipitation cycles.

This work discloses the potential of MEA solvoleaching combined with sulfide precipitation as an alternative to overcome the challenges in the metallurgical processing of chrysocolla ore.