Abstract:With seafloor polymetallic nodules as raw materials, ternary cathode material precursor Ni_0.5Co_0.2Mn_0.3(OH)₂ was prepared through a process of sulfuric acid leaching-purification-precipitation. In the process of sulfuric acid leaching, the effects of temperature, liquid-solid ratio, sulfuric acid concentration and leaching time on the leaching efficiency of nickel, cobalt and manganese were investigated. The leaching kinetics of nickel, cobalt and manganese were explored. The results show that the leaching efficiencies of nickel and cobalt are greater than 95%, and that for manganese is only 6.43% under the conditions of temperature of 200 ℃, liquid-solid ratio of 6:1, sulfuric acid concentration of 350 g/L, and leaching time of 90 min. Nickel and cobalt are selective leaching. At 120-200 ℃, the leaching process of Mn is controlled by diffusion with apparent activation energy of 10.64 kJ/mol. The leaching processes of Ni and Co are controlled by both diffusion and chemical reaction with apparent activation energy of 27.60 and 38.16 kJ/mol, respectively. Fe³⁺ ion in the leaching liquor is removed using sodium jarosite, copper is removed with manganese sulfide, and aluminum is precipitated as aluminum hydroxide as well as calcium is extracted by P204. A mixture of pure nickel sulfate, cobalt sulfate and manganese sulfate is then obtained through solvent extraction. The spherical Ni_0.5Co_0.2Mn_0.3(OH)₂, ternary cathode material precursor, is prepared by ammonia-sodium hydroxide coprecipitation after adjusting the molar ratio of nickel sulfate, cobalt sulfate and manganese sulfate.

Key words: ternary precursor; cathode material precursor; seafloor polymetallic nodules; leaching; impurity removal