A comparative study of different leaching processes for the extraction of Cu, Ni and Co from a complex matte

摘要

The extraction behaviors of Cu, Ni and Co from a complex matte under different leaching conditions have been discussed. The synthetic Cu-Ni-Co-Fe-S matte was prepared by melting the pure metals. The matte contained 24.95% Cu, 35.05% Ni, 4.05% Co, 11.45% Fe, 24.5% S, similar composition as is expected to be obtained by reduction smelting of the Pacific Ocean nodules followed by sulphidisation of the alloy. The different phases identified are CuFeS_2, CuS_2, (FeNi)_9S_8, (FeNi)S_2, Ni_9S_8, Ni_3S_2, (CoFeNi)_9S_8 and Co metal. The merits and demerits of each process of dissolution i.e., H_2SO_4/oxygen pressure leaching, atmospheric FeCl_3 leaching, NH_4OH/(NH_4)_2SO_4 pressure leaching are discussed in detail. Out of the three, the H_2SO_4/oxygen pressure leaching process is found to be the most suitable with more than 99% metal extraction efficiency within 1 h of leaching time. From the X-ray diffraction analysis, the different undissolved phases corresponding to different leaching processes have been identified. The metal extraction efficiency decreased in case of atmospheric FeCl_3 leaching and NH_4OH/(NH_4)_2SO_4 pressure leaching processes due to the formation of product layer such as elemental sulfur and goethite, respectively.