Characterization and leaching studies on Cu-Ni-Co matte obtained from copper converter slag

Abstract

A typical sample of Cu-Nl-Co matte obtained by pyritic smelting of copper converter slag was leached in sulphuric acid medium both at ambient and elevated pressures. The chemical composition of the matte was : 32.5 % Cu, 8.45 % Ni, 2.3 % Co, 27.5 % Fe and 16 % S. By leaching the matte at 358 K with 1M H2SO4, about 73 % Co and 86 % Ni could be dissolved. Copper dissolution was not significant under these conditions. Almost complete dissolution of metal values could be achieved by treating the matte under the following conditions: temperature 383 K, H2SO4 0.68M, P-O2 707 kPa and retention time 2h. Iron extraction under these conditions was about 19 % and most of the sulphur remained in the residue as spherules. with the increase of leaching temperature to 425 K, extractions of Cu, Ni, and Co decreased. Depending on the leaching conditions, the residues consisted of powders, spherules (black, brown and yellow) and irregular shaped metal like pieces. A detailed work on the characterization of residues using X-ray diffraction and SEM techniques has been presented.