Copper extraction from chloride solution by solvating and chelating extractants

The extraction of Cu(II) from chloride solutions at constant water activity a(w) and constant total concentration sigma of species dissolved in the aq ueous phase by di(2-ethylhexyl)pyridine-2,4-dicarboxylate (S), ACORGA CLX-5 0 (S) and LM 54 (HL) used alone and in 1:1 mole/mole mixtures was studied. It was found that solvating reagents have a high ability of copper extracti on from chloride solutions of low water activity and their extraction abili ty strongly depends on the chloride concentration. The extraction of copper (II) by LIX 54 is low in all systems studied (pH 2.4-3.9) and only slightly affected by chloride concentration. In the region of chloride concentratio n equal to 3-4 M approximately 90 and 50% of extracted copper is bound in t he solvate with ACORGA CLX-50 for a(w) = 0.617 and sigma = 12 M, and a(w) = 0.835 and sigma = 8 M, respectively. Scrubbing with water at equilibrium p H above 4 permits almost complete transfer of chloride ions into the aqueou s phase with the simultaneous conversion of copper(II) from the solvate CuC l2S2 in the chelate CuL2. Copper can be then stripped with 25-75 g/L H2SO4 and the organic phase recycled.