Solvometallurgical Process for the Recovery of Copper from Chrysocolla in Monoethanolamine
Nor Kamariah, Panagiotis Xanthopoulos, Koen Binnemans, Jeroen Spooren
Abstract
Difficulties in beneficiation and hydrometallurgical processing limit the potential of chrysocolla as a copper ore mineral. Solvoleaching in a solution of 3 M NH 4 Cl in monoethanolamine (MEA) enabled efficient and selective copper extraction from high-grade chrysocolla ore. The leaching temperature was a decisive parameter; leaching at elevated temperatures progressively improved copper extraction yields, with the highest yield of 88% obtained by leaching at 100 °C for 4 h. SEM–EDX analysis indicated the presence of copper-depleted silica surface layers in residual copper-containing chunks that eventually hinder 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 yields. FTIR analysis suggests that the leaching mechanism occurs via coordination of the amine functional group of MEA to copper(II) ions. The ammonium chloride salt in the lixiviant is expected to have provided chloride counteranions that kept the formed copper–ammine complex in solution. Copper was recovered from the pregnant leach solution by sulfide precipitation with an aqueous (NH 4 ) 2 S solution. Copper was precipitated as a covellite phase, with more than 98% recovery yield. Furthermore, reusability of the lixiviant was demonstrated by four leaching–precipitation cycles.