Development of bifunctional anion-exchange resins with improved selectivity and sorptive kinetics for pertechnetate: Batch-equilibrium experiments

A novel class of strong-base anion-exchange resins, bearing two different t ypes of exchange sites, is described. These bifunctional resins have anion- exchange sites composed of two separate and differently sized trialkylammon ium groups. In pertechnetate (TcO4-) uptake experiments from a solution mat rix containing anions commonly encountered in groundwater, bifunctional res ins containing exchange sites derived from tri-n-hexylamine in combination with either triethylamine, tri-n-propylamine, or tri-n-butylamine were show n to possess superior 24-h distribution ratios (K-d) for pertechnetate over all monofunctional anion-exchange resins (derived from a single trialkylam ine) examined. For example, although monofunctional resins containing a tri -n-hexylammonium exchange site possessed excellent selectivity for pertechn etate over other anions, the exchange kinetics were poor. The superior perf ormance of these resins can be attributed to the combination of a large tri alkylammonium site for enhanced selectivity for large anions and a smaller trialkylammonium site for the retention of good exchange kinetics.