Three step solvent extraction process has been developed for processing the leach liquor generated via NH3 / SO2 leaching route for ocean nodules. The sulphate leach liquor contains number of impurities like iron, copper and zinc in addition to nickel and cobalt, the metals of interest. In the first step, impurity metals are removed by extraction with partially saponified 0.5M di-(2-ethyl hexyl) phosphoric acid (D2EHPA) and 5% isodecallol in kerosene. The second step carries out separation of nickel and cobalt present in the raffinate solution from the first step by using partially saponified 0.5M 2- ethyl hexyl phosphonic acid mono∼2-ethylheA"Y1 ester (PC-88A) and 5% isodecanol in kerosene. The pure cobalt solution is recovered by stripping the loaded solvent wi.th sulphuric acid. The third step comprises of integrated solvent extraction-electrowinning (SX-EW) circuit in which nickel from raffinate of second step is extracted with partially saponified D2EHPA and 5% isodecanol in kerosene and stripped with spent electrolyte to generate pregnant electrolyte which· is recycled to the integrated EW cell. The solvent extraction process has been optimized and tested to process feed solution at flow rate of 60 1/hr. to give pure nickel and cobalt solution with purities higher than 99.9% and recoveries over 99%.


Ocean nodules have become a focus of global attention for extraction of manganese, cobalt, nickel, copper and various other rare metals. Since India has no primary resources of Ni or Co and is at present importing these metals, ocean nodules become the most promising resource of these metals. Both nickel and cobalt are having important industrial and strategic applications. Cobalt finds uses in making cutting, wear resistant and hard facing alloys, permanent strong magnets, catalysts, corrosion resistant alloys, super alloys and body implants. CO60 is used in radiography and sterilization of food and surgical equipments.

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