Studies on the recovery of nickel and cobalt from copper depleted converter slag

Abstract

Two different processes were investigated to recover nickel and cobalt values from a residual material generated after separation of most of copper from copper converter slag by segregation roasting. In the first approach, the various steps involved were segregation roasting of copper depleted converter slag, magnetic separation and melting of magnetic fraction. The effect of various parameters like time and temperature of roasting, percentage and type of carbonaceous material and chloridising agent, were studied. Although it was possible to recover 80% nickel and 52% cobalt under the optimum experimental condition, substanstial amount of the metal values were found to be entrapped in the slag and thus posed separation problems. The second approach involves two leaching steps: first with ammonia-ammonium carbonate to recover residual copper and then with dilute H2SO4 to extract Ni and Co. It was possible to achieve a recovery of 82% Ni and 97% Co in sulphate from under optimum leaching conditions of ammonia/ammonium carbonate ratio, acidity and duration.