Separation of cobalt and nickel from sulfate media was investigated, using a extraction system of 30% 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507)+15% trioctyl/decylamine (N235)+55% sulfonated kerosene. About 41 wt% Co2+ was extracted with 1.6 wt% co-extraction of Ni2+ at O/A ratio of 2:1. Scrubbing of Ni2+ and stripping of Co2+ could be achieved from the loaded organic phase, using water and 0.05 mol/L H2SO4, respectively. Cobalt extraction percentage decreased with increasing Mg2+ concentration, but this influence was negligible as [Mg2+] < 0.1g/L. The favorable equilibrium pH was 4-4.8. A different E-pH curve was observed in the P507-N235 system compared to the saponified P507 system.