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 studied as a function of aqueous pH, equilibration time, temperature, counter anion (sulphate) and extractant concentration. The stripping of nickel from loaded organic phases using H2SO4 has also been studied as a function of acid concentration, equilibration time and temperature. Nickel extraction is very sensitive to equilibrium pH and the extraction decreases beyond pH 9.0. The increase of temperature decreases nickel extraction (Delta H degrees = -43.8 kJ/mol). The presence of sulphate (as ammonium sulphate) in the aqueous solution decreases nickel extraction. The extraction equilibrium constant for nickel was determined numerically to be 4.10(-14) and experimental data can be explained assuming the formation of NiR2 species in the organic phase (R represented the extractant). Stripping of nickel can be achieved effectively using diluted H2SO4 solutions and temperature has little effect on nickel stripping (Delta H degrees = 10.9 kJ/mol). (C) 1998 Elsevier Science B.V.