Recovery of Pure Co(II) and Ni(II) Solutions from Synthetic Sulfate Leach Liquor of Laterite Ores by Precipitation and Solvent Extraction

Recovery of nickel and cobalt from laterite ores is important to meet the demand for these metals. In this work, a process was developed for the separation of metal ions from synthetic sulfate leach liquor of laterite ores containing Fe(III), Al(III), Ni(II), Co(II), Ca(II), Mg(II), and Mn(II). First, Fe(III) and Al(III) were removed by precipitation of their hydroxides by adjusting solution pH and then Mn(II) was removed from the filtrate by oxidative precipitation with NaClO. Sequentially, Co(II) and Ni(II) from the filtrate containing Mg(II) and Ca(II) were separated by selective precipitation of CoS and NiS by adding Na2S solution, leaving Ca(II) and Mg(II) in the filtrate. The mixed precipitates of CoS and NiS were completely dissolved by 0.1 M HCl solution containing NaClO. Co(II) can be separated from Ni(II) present in the HCl solution by either oxidative precipitation with NaClO or selective extraction with saponified Cyanex 272. Optimum conditions for these procedures were obtained. Continuous experiments indicated that the purity of Co(II) and Ni(II) solutions was higher than 99%.