Separation of Cu, Co, Ni and Mn from acid leaching solution of ocean cobalt-rich crust using precipitation with Na2S and solvent extraction with N235

In order to effectively separate and recover copper, cobalt, nickel and manganese from the leaching solution of ocean cobalt-rich crusts, a process of selective precipitation and extraction using precipitation with Na2S solution and solvent extraction with N235 extractant, was proposed. The optimum separation and recovery process conditions were determined through single factor condition experiments. The results show the precipitation efficiency of copper can reach 99.87%, while the precipitation efficiency of cobalt and nickel was 1.23% and 1.08%, respectively, at the initial pH of 0.60. Similarly, under the condition of initial pH of 4.00, 99.18% cobalt and 98.31% nickel were precipitated and only 0.89% manganese was co-precipitated. The mixed cobalt-nickel precipitation was completely dissolved with HCl solution, then N235 extractant was used to extract cobalt from solution. The extraction efficiency of cobalt can exceed 99% though three stages countercurrent extraction under optimal extraction conditions (chloride ion concentration of 9 mol/L, the N235 concentration of 30% (v/v), the phase ratio (O/A) of 2, and at 298.15 K for 8 min). In addition, thermodynamic calculations showed that the extraction of cobalt from acid leaching solution of ocean cobalt-rich crust with N235 as the extractant was an exothermic reaction.