Development of Bifunctional Anion-Exchange Resins with Improved Selectivity and Sorptive Kinetics for Pertechnetate:  Batch-Equilibrium Experiments

Abstract

A novel class of strong-base anion-exchange resins, bearing two different types of exchange sites, is described. These bifunctional resins have anion-exchange sites composed of two separate and differently sized trialkylammonium groups. In pertechnetate (TcO 4 - ) uptake experiments from a solution matrix containing anions commonly encountered in groundwater, bifunctional resins containing exchange sites derived from tri- n -hexylamine in combination with either triethylamine, tri- n -propylamine, or tri- n -butylamine were shown to possess superior 24-h distribution ratios ( K d ) for pertechnetate over all monofunctional anion-exchange resins (derived from a single trialkylamine) examined. For example, although monofunctional resins containing a tri- n -hexylammonium exchange site possessed excellent selectivity for pertechnetate over other anions, the exchange kinetics were poor. The superior performance of these resins can be attributed to the combination of a large trialkylammonium site for enhanced selectivity for large anions and a smaller trialkylammonium site for the retention of good exchange kinetics.