SOLVENT-EXTRACTION EQUILIBRIUM OF NICKEL WITH LIX-54

Nickel extraction from ammoniacal media, containing initially 0.5 g/l of nickel, by LIX 54 in an aliphatic diluent, Iberfluid, has been stud ied as a function of aqueous pH, equilibration time, temperature, coun ter anion (sulphate) and extractant concentration. The stripping of ni ckel from loaded organic phases using H2SO4 has also been studied as a function of acid concentration, equilibration time and temperature. N ickel extraction is very sensitive to equilibrium pH and the extractio n decreases beyond pH 9.0. The increase of temperature decreases nicke l extraction (Delta H degrees = -43.8 kJ/mol). The presence of sulphat e (as ammonium sulphate) in the aqueous solution decreases nickel extr action. The extraction equilibrium constant for nickel was determined numerically to be 4.10(-14) and experimental data can be explained ass uming the formation of NiR2 species in the organic phase (R represente d the extractant). Stripping of nickel can be achieved effectively usi ng diluted H2SO4 solutions and temperature has little effect on nickel stripping (Delta H degrees = 10.9 kJ/mol). (C) 1998 Elsevier Science B.V.