Development of a new cobalt recovery process at the Surigao Nickel Refinery

Abstract

Nonoc's mixed NiCo sulphides leached in a NH 3-(NH 4) 2CO 3 solution under optimized conditions resulted in over 95% Ni and Co extractions. Other impurities such as Fe, Mn, Mg and SiO 2 were rejected as insoluble oxides. The filtered liquor being relatively free of impurity elements considerably simplifies the solution purification route. The problematic jarosite iron precipitation and manganese removal steps inherent in the acid leaches were avoided. Nickel and cobalt separation can be staged favorably using LIX 64N. Ni loaded into the organic is stripped with mildly strong H 2SO 4 and recovered through the existing Nickel Refinery. The recovery of Co in the raffinate is by the solvent extraction-electro-winning route instead of by the traditional Co powder production by hydrogen reduction in the NH 3-(NH 4) 2SO 4 system. Preliminary cost data indicate that a capital investment of $10 million is required for a plant rated at 2.3 million lb. Co cathode per year. The ROI of the project at $11.70/lb. Co and and $2.20/lb. Ni is only four months.