Solvent Extraction of Copper(I) and Copper(II) from Aqueous Halide Solutions with Tetrabutylammonium Ions into Chloroform

Abstract

Abstract The solvent extraction of copper(I) and copper(II) from 1 mol dm−3 Na(X, NO3), where X−is Cl−, Br−, or I−, as ion-pairs of anionic halide complexes with tetrabutylammonium ions (tba+) into chloroform was studied in the absence and presence of a reducing agent, ascorbic acid. The extraction of copper(II) with 2-thenoyltrifluoroacetone (Htta) in chloroform from these aqueous solutions was also studied. In the absence of ascorbic acid, the extraction of copper which was added as Cu2+ with tba+ was negligible from chloride and bromide solutions but tba+CuIII3− and (tba+)2CuIII42− were extracted from iodide solutions. In the presence of ascorbic acid, the extraction of tba+CuIX2− was found from all of these halide solutions. Only copper(II) was extracted with Htta from these solutions. The distribution ratio was lower when the halide concentration was higher due to formation of copper(II) complexes in the absence of ascorbic acid and it was much lower in the presence of this reducing agent due to formation of copper(I) complexes, which were stabler than the copper(II) complexes. From the extraction data with tba+ and with Htta, the formation constants of copper(I) and copper(II) halide complexes from Cu2+ in the aqueous phase as well as the extraction constants of certain complexes into the organic phase were determined. It was concluded that the dominant metal species in the aqueous phase was Cu2+ when the halide concentration was low even in the presence of the reducing agent and thus copper(I) anionic complexes were extracted into the organic phase and the molar ratio of copper(I) complex species to Cu2+ in the aqueous phase was higher at higher halide concentrations.