Use of Raman Spectroscopy to Evaluate the Selectivity of Bifunctional Anion Exchange Resins for Perchlorate

Abstract

Raman spectroscopy is used to evaluate the selectivity of two bifunctional anion exchange resins, Purolite A-530 and Amberlite PWA-2. It was found that the adsorption of anions on the resins is described by a Frumkin isotherm, which is determined by the ion pair constant, K, and the Frumkin parameter, g. The ion pair constant, K, is a measure of the strength of interaction between the resin and the anion and the Frumkin parameter, g, takes into account interactions between adsorbed anions. Although both resins have a polystyrene backbone and trihexylammonium and triethylammonium functional groups, the Purolite A-530 resin exhibits greater selectivity for perchlorate. The only discernable differences between the two resins is that the Amberlite PWA-2 has a higher trihexylamine content and the Purolite A-530 resin exhibits greater cross-linking. How the trihexylamine/triethylamine content and the degree of cross-linking affects the performance of these resins is discussed.