Accumulation mechanisms for contaminants on weak-base hybrid ion exchange resins

• Published in: Journal of hazardous materials 2023-10, Vol.459, p.132165-132165, Article 132165
• Main Authors: Saslow, Sarah A., Cordova, Elsa A., Escobedo, Nancy M., Qafoku, Odeta, Bowden, Mark E., Resch, Charles T., Lahiri, Nabajit, Nienhuis, Emily T., Boglaienko, Daria, Levitskaia, Tatiana G., Meyers, Peter, Hager, Jacqueline R., Emerson, Hilary P., Pearce, Carolyn I., Freedman, Vicky L.
• Format: Article
• Language: English
• Subjects: Chromium; Iodine; ResinTech SIR-700-HP; Technetium; Uranium
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.132165

Mechanism of hexavalent chromium removal (Cr(VI) as CrO42-) by the weak-base ion exchange (IX) resin ResinTech® SIR-700-HP (SIR-700) from simulated groundwater is assessed in the presence of radioactive contaminants iodine-129 (as IO3-), uranium (U as uranyl UO22+), and technetium-99 (as TcO4-), and common environmental anions sulfate (SO42-) and chloride (Cl-). Batch tests using the acid sulfate form of SIR-700 demonstrated Cr(VI) and U(VI) removal exceeded 97%, except in the presence of high SO42- concentrations (536 mg/L) where Cr(VI) and U(VI) removal decreased to ≥ 80%. However, Cr(VI) removal notably improved with co-mingled U(VI) that complexes with SO42- at the protonated amine sites. These U–SO42- complexes are integral to U(VI) removal, as confirmed by the decrease in U(VI) removal (TcO4->IO3-), geometry, and charge density. For these reasons, 39% and 69% of TcO4- and 17% and 39% of IO3- are removed in the presence and absence of Cr(VI), respectively. [Display omitted] •SIR-700 weak-base IX resin with SO42- parent anion removes ≥ 97% Cr(VI) and U(VI).•Cr(VI) is reduced to Cr(III)(OH)3 phase at secondary alcohol sites.•Other anions also removed by IX and reduction, following the trend Cr(VI) > Tc(VII) > I(V).•U(VI) removed by complexation with SO42- parent anion, Cl--form had low U(VI) uptake.