Enhanced selectivity of imidazolium-based anion exchange resins for technetium-99 and rhenium removal
Luyang Xie, Jie Li, Wenjuan Xue, Haifeng Zou, Jie Wu, Zuzhuo Zhang, Yanhua Song, Wenfu Yan, Xueqi Fu, Shuao Wang, Donghai Mei
Abstract
The selective removal of technetium-99 ( 99 Tc) from radioactive wastewater remains a significant challenge due to its stringent adsorption requirements. In this study, we synthesized a series of imidazolium-functionalized anion exchange resins— N -methyl ( MeMiMCl ), N -butyl ( BuMiMCl ), and N -hexyl ( HeMiMCl ) imidazolium derivatives—to enhance the selectivity and stability for pertechnetate ion ( 99 TcO 4 − ) capture. These resins exhibited high adsorption capacities for Re(VII): 691 mg·g −1 for MeMiMCl , 689 mg·g −1 for BuMiMCl , and 653 mg·g −1 for HeMiMCl . Corresponding distribution coefficients were also significant, reaching 5.27 × 10 6 mL·g −1 for MeMiMCl , 9.99 × 10 5 mL·g −1 for BuMiMCl , and 3.12 × 10 6 mL·g −1 for HeMiMCl . The materials showed excellent chemical and radiolytic stability. Under competitive adsorption scenarios, where NO 3 − to ReO 4 − molar ratios reached 5000: 1, BuMiMCl and HeMiMCl maintained high ReO 4 − removal efficiencies. Their performance was 11 times higher than that of the commercial ZGANR170 resin, highlighting their superior selectivity. Density functional theory calculations revealed that the enhanced selectivity results from stronger interactions between the 99 TcO 4 − anions and imidazolium cations with longer alkyl chains. Furthermore, these resins effectively removed 99 TcO 4 − from simulated Hanford and Savannah River Site waste streams. Due to their high selectivity, stability, and cost-effectiveness, the developed imidazolium-based resins show strong potential for practical applications in nuclear wastewater treatment.