Solvent Extraction Process For Recovery Of Nickel And Cobalt From Ocean Nodules Leach Liquor

摘要

Three step solvent extraction process has been developed for processing the leach liquor generated via NH_3/SO_2 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 percent isodecanol 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-ethyl hexyl ester (PC-88A) and 5 percent isodecanol in kerosene. The pure cobalt solution is recovered by stripping the loaded solvent with 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 percent 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 l/hr. to give pure nickel and cobalt solution with parities higher than 99.9 percent and recoveries over 99 percent.