Cobalt recovery from the slag of nickel pig iron using tubular electrode in the electrowinning process

Abstract

Nickel pig iron is a raw material in stainless steel manufacturer. Nickel laterite ore is processed becomes nickel pig iron as a primary product and slag as solid waste. However, this slag contains cobalt that is more valuable than a nickel. In this work, the solvent extraction method was used to separate cobalt from its impurities in slag. Cobalt ion in this process is in the aqueous phase from the solvent extraction product. Electrowinning is one method which able to recover cobalt from this aqueous phase. In this work, the tubular electrode is used to improve the performance of electrowinning. This experiment used four parameters to increase the cobalt recovery in the electrowinning, namely applied voltage, electrolysis time, temperature, and boric acid concentration. The Taguchi design experiment was used to analyze and optimize these parameters. From the Taguchi analysis results, the optimum condition of electrowinning using tubular electrode was at 5 volts, 2 hours, 50° C, and 0.5 M boric acid.