Separation of nickel and cobalt from nitrate leaching solutions of laterite ore by solvent extraction using trihexyltetradecylphosphonium bis (2,4,4-trimethyl pentyl) phosphinate

This study used solvent extraction to separate nickel and cobalt from nitrate leaching of mixed nickel-cobalt oxalate precipitate (MOP). Laterite ore was first leached using citric acid, and then leaching filtrate was mixed with oxalic acid to produce MOP. MOP was releached using nitric acid (1M) to prepare the aqueous phase as a feed for solvent extraction. Solvent extraction used the extractant trihexyltetradecylphosphonium bis (2,4,4-trimethyl pentyl) phosphate (Cyphos®IL 104) in kerosene. Solvent extraction experiments were conducted in the pH range of 6 to 7.6 (O/A ratio = 1 at 15 min). After separation, the concentration of the aqueous phase was analyzed using an ICP-Optical Emission Spectrometer (ICP-OES) to measure cobalt and nickel content. The results showed that the highest extraction efficiency of cobalt and nickel was obtained at pH 7.2, 99.97%, and 32.57%, respectively. At this optimum condition, the separation factor obtained for cobalt was 8008.66 and for nickel 0.0001, while cobalt was 3868.00 and nickel 0.48 for the ion distribution obtained. It indicates that at this condition, the extractant can extract cobalt to the organic phase, and nickel remains in the aqueous phase.