Evaluation of Gibbs free energy for the transfer of a highly hydrophilic ion from an acidic aqueous solution to an organic solution based on ion pair extraction

A method to determine the standard Gibbs free energy for the transfer, DeltaG(tr)degrees, of a highly hydrophilic metal ion from an aqueous solution, W, in the presence of high concentration of H+ to an organic solution, O, was proposed based on the theoretical consideration of the distribution process of ions between W and O. The usefulness of the proposed method was verified experimentally by comparing DeltaG(tr) degreesof Mg2+ determined by the method with that obtained by voltammetry for the ion transfer at the W\O interface. The O examined were nitrobenzene (NB) and 1,2-dichloroethane (DCE). By applying the proposed method, DeltaG(tr) degrees of NpO2+, UO2+, NpO22+ and PuO22+ from an acidic W to NB were determined. (C) 2002 Elsevier Science B.V. All rights reserved.