Transfer of nickel from sodium sulphate solutions to the spent electrolyte through solvent extraction and stripping

Studies on the separation of nickel from concentrated solutions containing sodium sulphate were carried out with di(2-ethylhexyl) phosphoric acid diluted with kerosene (mostly aliphatic). Increase in extractant concentration, extent of neutralisation and organic to aqueous phase ratio increase the extraction of nickel. The plot of log D vs. log [extractant] is linear with a slope of 2.3, indicating that the extracted species is probably NiA2. Employing 0.4 M D2EHPA, nickel was extracted to the extent of 99.6% in three counter-current stages at an aqueous to organic phase ratio of 1:4. Nickel was stripped using the spent electrolyte from the loaded organic phase in three counter-current stages at an aqueous to organic phase ratio of 2.2:1 to the extent of 99.8%. Temperature in the range of 30¯60°C has marginal effect on the extent of nickel stripping. The pregnant electrolyte with a pH of 4.2 and enriched by about 3.9 kg/m3 of nickel is suitable for electrowinning to produce nickel cathode.