Solvent extraction separation and recovery of cobalt and nickel from sulphate medium using mixtures of TOPS 99 and TIBPS extractants

We report in this paper the solvent extraction separation of cobalt and nickel from synthetic sulphate solutions using TOPS 99 and TIBPS mixtures diluted in kerosene. The feed contains 1.061 g/L Co and 1.187 g/L Ni. Extraction experiments with synergistic mixture of extractants showed highest separation factor of 12,245 with 0.1 M TOPS 99 and 0.05 M TIBPS at pH 1.1. McCabe–Thiele plot for Co extraction with 0.1 M TOPS 99 and 0.05 M TIBPS extractants mixture indicated the necessity of three theoretical stages for >99% Co extraction at an aqueous to organic phase (A/O) ratio of 2. A three stage counter current extraction simulation test conducted at pH 1.1 with 0.1 M TOPS 99 and 0.05 M TIBPS mixture, confirmed Co extraction of 99.5% with Ni co-extraction of 0.02%. The results demonstrated that the addition of TIBPS–TOPS 99 acts as a synergist for Co extraction and antagonist for Ni.