Effect of the Chain Length of Carboxylic Acids and Alcohols on the Extraction of Copper(II) with the Acids Using Alcohols as Solvents

The solvent extraction of copper(II) with aliphatic carboxylic acids (CH3(CH2)nCOOH : n = 2—7) in alcohols (CH3(CH2)nOH : n = 4—7) was carried out at 25 °C and an aqueous ionic strength of 0.1 mol dm-3 (NaClO4). Each extraction equilibrium for these systems was determined in detail by a slope analysis and a curve-fitting method. In all of the extraction systems, except for butanoic acid ones, copper(II) carboxylates were found to be extracted as monomeric and dimeric species: CuA2, Cu2A4, and Cu2A4(HA)2. The dimerization and the adduct formation constants of copper(II) carboxylates in the organic phase were estimated. The dimerization and the adduct formation constants in the organic phase were found to be dependent on the chain length of the acids and alcohols, although the extraction constant of CuA2 were found to be independent of their chain length.