Voltammetric study of the transfer of keggin-type heteropolyanions across the nitrobenzene/water interface

Abstract

The transfer of Keggin-type heteropolyanions, α- and β-[XM 12O 40] 3−/4−, at the nitrobenzene (NB)/water (W) interface has been studied by ion transfer voltammetry (X = Si, Ge, P, As; M = Mo, W). For the tetravalent anions with Si and Ge as the central heteroatoms, well-developed waves due to their phase transfer were observed. On the other hand, the trivalent anions with P and As gave no waves in the polarizable potential range, but showed an increase in the final current rise due to their transfer from NB to W. From the voltammetric data, it has been found that the Gibbs transfer energy, Δ G tr XXX,NB→W, of the heteropolyanions depends primarily on the ionic charge. The extraction behaviour of these heteropoly-acids has been discussed on the basis of the voltammetric data.