Hybrid resins for simultaneous removal of multiple groundwater contaminants

This study examines a wide range of hybrid ion exchange (IX) resins that simultaneously remove multiple contaminants from groundwater via anion exchange and an additional mechanism, such as chemical reduction or adsorption. Hybrid resins aim to overcome pump-and-treat operational limitations when using single-contaminant selective IX resins. Performance of hybrid and weak base hybrid IX resins for removing contaminants, including uranium (U as uranyl carbonates UO 2 (CO 3 ) x 2–2x ), technetium-99 (as TcO 4 - ), and hexavalent chromium (Cr(VI) as CrO 4 2- ), as well as incidental removal of iodine-129 (as IO 3 - ), is compared to the performance of strong base anion exchange resins used to treat these contaminants individually. Batch and column tests were performed using ultrapure water and/or a simulated groundwater solution representative of the U.S. Department of Energy’s Hanford Site . Several strong base and hybrid candidate resins could remove TcO 4 - . The weak base hybrid resin SIR-700 in its sulfate form performed the best for both Cr(VI) and U removal, yet demonstrated poor TcO 4 - removal. Removal of IO 3 - by anion exchange resins is typically not efficient. In this study, few hybrid resins demonstrated improved IO 3 - uptake compared to their parent resins because it was outcompeted by other more abundant anions. While the SBG1-Ce resin removed the most IO 3 - from simulated Hanford groundwater in the presence of all four contaminants, the cerium hybrid resin SIR-110-MP-Ce removed both TcO 4 - and the second-most IO 3 - of the resins evaluated in column tests. IO 3 - in the presence of the other contaminants and natural groundwater anions, like sulfate, is not competitive for removal by ion exchange. Removal of IO 3 - is proposed to occur via adsorption as an inner- or outer-sphere complex to the hybrid metal phase. Optimizing access to these phases and increasing hybrid metal loading are expected to improve incidental IO 3 - removal. • Hybridized ion exchange resins can remove multiple metal aqueous contaminants. • ResinTech’s weak base hybrid resin SIR-700-HP removes uranyl carbonates and chromate. • ResinTech’s cerium hybrid SIR-110-MP-Ce removes pertechnetate and iodate.