Transfer of divalent metal ions into the organic phase of the systems water–chloroform–ZnCl2–CdCl2–HgCl2–NaOH–(NaCl)–n-alkyltri(oxyethylene)carboxylic acid

Abstract

The influence of the length of an n-alkyl chain incorporated into the molecule of an n-alkyltri(oxyethylene) carboxylic acid of a general formula CnH(2n+1)(OCH2CH2)3OCH2CO2H(n = 6, 8, 10, and 12, respectively) on transfer of the zinc group element ions into chloroform was investigated. Metal ions were transferred from the aqueous solutions of ZnCl2, CdCl2, and HgCl2 at initial concentrations of 0.835 mM and 1.67 mM with, and without, added NaCl. From the aqueous solutions to which no NaCl was added, the selectivity of transfer of divalent metal ions into the organic phase was low.The selectivity of transfer of the divalent metal ions improved remarkably when NaCl was added to the aqueous phase due to the chemical equilibria involving complexation of the divalent metal ions by Cl−, OH−, and n-alkyltri(oxyethylene) carboxylic acid. In most systems (with NaCl added), Zn(II) was separated from Cd(II) and Hg(II). Less lipophilic n-alkyltri(oxyethylene) carboxylic acids (with a shorter n-alkyl chain incorporated) exhibited higher selectivity and efficiency as divalent metal ion carriers.