Process development for the separation of copper(II), nickel(II) and zinc(II) from sulphate solutions by solvent extraction using LIX 84 I

Abstract

Development of a solvent extraction flow sheet for the separation and recovery of Cu(II), Ni(II) and Zn(II) using LIX 84 I as an extractant from sulphate solutions was investigated. Extraction of the metals depends on the equilibrium pH of the aqueous phase and increases with rise in equilibrium pH. Based on the difference in their extraction behavior as a function of equilibrium pH of the aqueous phase, it was possible to separate and recover these metals. Their extraction behavior clearly demonstrates the application of LIX 84 I as the extractant for the selective separation of Cu(II), Ni(II) and Zn(II) in pure form. The copper extraction isotherm was obtained by contacting the metal solution and 0.05 M LIX 84 I at different aqueous to organic (A:O) phase ratios at an equilibrium pH of 4.0. The McCabe–Thiele plot suggested that quantitative copper extraction is achievable in two counter-current stages (C–C) at A:O phase ratio of five, which gave 99.4% copper extraction efficiency. The results of two-stage stripping simulation for 0.745 gpl of Cu-loaded organic (LO) carried out at O:A ratio of 1.5:1 with 2 M H 2SO 4 gave copper stripping efficiency of 99.94%. Copper in the strip solution was enriched by more than seven times. The extraction of nickel with the same concentration of LIX 84 I at an equilibrium pH of 7.50 at A:O phase ratio of 1:1.1 in two stages gave nickel extraction efficiency of 99.4%. A two-stage counter-current stripping simulation (CCSS) for nickel LO at A:O phase ratio at 1:1 gave nickel stripping efficiency of 99.93%. Further extraction of zinc with the same concentration of LIX 84 I at an equilibrium pH of 9.0 at A:O phase ratio of unity for two stages gave zinc extraction efficiency of 99.81%. A two-stage counter-current stripping simulation for zinc LO at A:O phase ratio of unity with 3 M H 2SO 4 gave zinc stripping efficiency of 99.7%. Based on the results, a complete solvent extraction flow sheet of the process was developed with extraction and stripping efficiencies >99.5%.