Magnetic separation-sulphuric acid leaching of Cu–Co–Fe matte obtained from copper converter slag for recovering Cu and Co

• The process was proposed on the basis of mineralogical analysis of matte.
• The matte was magnetic separated to produce magnetically susceptible concentrate.
• Cobalt is mainly concentrated in concentrate and then selectively leached.
• Most copper remained in tailings and residual copper in concentrate was not leached.
• Tailings and leaching residue were return for copper smelting.

Cu–Co–Fe matte obtained from copper converter slag by reductive-sulfidizing smelting was treated by magnetic separation-sulphuric acid leaching (MS-SAL) process to recover the metal values, copper and cobalt. The MS-SAL process was proposed on the basis of mineralogical analysis of matte, which showed that the main copper-bearing phases were bornite and chalcocite (non-magnetic substances), and the main cobalt-bearing phase was cobalt–iron alloy (magnetic substances). The matte sample was crushed, wet ground and then magnetic separated to produce magnetically susceptible concentrate (mainly Co–Fe alloy). 95.75% of cobalt was recovered by magnetic separation and 87.8% of copper and 44.39% of iron remained in the tailings. The concentrate was leached further by sulphuric acid. Under the optimum conditions of 1.15 times the stoichiometric amount of sulphuric acid, 1 h of leaching time and temperature 80 °C, 99.81% of cobalt in concentrate was selectively leached into the solution while the 99.86% of copper remained in residue. The tailings containing mainly bornite and chalcocite and the leaching residue containing mainly metal copper were treated by ore proportioning with copper concentrate and fed to the copper smelting furnace. In this process, cobalt in matte was selectively extracted and the copper was almost entirely recovered for copper smelting rather than extracted from leaching liquor as in existing copper matte leaching technologies. Recovery yields of cobalt and copper by MS-SAL were 95.57% and 99.98%, respectively.