Development of novel bifunctional anion-exchange resins with improved selectivity for pertechnetate sorption from contaminated groundwater

The present study evaluated a new class of bifunctional anion-exchange resins with improved selectivity and sorption kinetics for removing pertechnetate (TcO₄^-) from contaminated groundwater. Both laboratory-column and field flow-through experiments were performed, and results indicated that superior performance of the bifunctional resins has been achieved through the use of two quaternary ammonium groups, one having long chains (trihexylamine) for higher selectivity for poorly hydrated large anions and one having shorter chains (triethylamine) for enhanced kinetics and exchange capacity. Field results indicated that the bifunctional resin performed ~5 times better than one of the best commercial monofunctional anion-exchange resins (e.g., Purolite A-520E) with respect to the removal of TcO₄^- from contaminated groundwater. Less than 3% of TcO₄^- breakthrough was observed after ~700 000 bed volumes (BV) of contaminated groundwater had been treated by the bifunctional resin column (at a flow rate of ~6 BV/min) at the U.S. Department of Energy's Paducah Gaseous Diffusion Plant site. The results also demonstrate that the new resin is particularly effective in removing low levels of TcO₄^- (e.g., at nmol/L range), and a cost saving may be realized by using the bifunctional resins for the treatment of large quantities of contaminated groundwater because of its increased selectivity, treatment efficiency, and longevity. The new resin may also be applied for the efficient treatment of other poorly hydrated large anions such as perchlorate (ClO₄^-) from contaminated groundwater or surface water.