Abstract:The recovery of Mn, Co and Ni from deep-sea manganese nodules was conducted by acid oxidative leaching and solvent extraction. The results indicate that pyrrhotite used during leaching can effectively facilitate the leaching out of manganese, cobalt and nickel. The leaching behaviors of Mn, Ni and Co were determined and the influences of temperature, leaching time and sulphuric acid concentration on leaching rate were also investigated. Co and Ni are precipitated from the leaching liquor by adding sodium sulfide into solution with agitation for 2 h at 50 ℃, and the manganese sulphate is obtained by concentrating the resulting solution. By re-dissolving the precipitates of cobalt and nickel, the separation of cobalt and nickel is performed using di(2-ethylhexyl) phosphoric acid (D2EHPA) for impurities elimination with 8 stages at organic-to-aqueous(O/A) volume ratio of 3׃5, and 2- ethylhexyl phosphonic acid mono-2-ethylhexyl ester (known as PC88A or P507) for cobalt extraction with 3 stages counter-current operations at O/A volume ratio of 2׃3 followed by their scrubbings and strippings, respectively. The final maximum recovery rates for manganese, cobalt and nickel are 85%, 75% and 78%, respectively.

Key words: sea nodule; pyrrhotite; extraction; nickel; cobalt; manganese