Creation of Cationic Polymeric Nanotrap Featuring High Anion Density and Exceptional Alkaline Stability for Highly Efficient Pertechnetate Removal from Nuclear Waste Streams

There is an urgent need for highly efficient sorbents capable of selectively removing ⁹⁹TcO₄^- from concentrated alkaline nuclear wastes, which has long been a significant challenge. In this study, we present the design and synthesis of a high-performance adsorbent, CPN-3 (CPN denotes cationic polymeric nanotrap), which achieves excellent ⁹⁹TcO₄^- capture under strong alkaline conditions by incorporating branched alkyl chains on the N3 position of imidazolium units and optimizing the framework anion density within the pores of a cationic polymeric nanotrap. CPN-3 features exceptional stability in harsh alkaline and radioactive environments as well as exhibits fast kinetics, high adsorption capacity, and outstanding selectivity with full reusability and great potential for the cost-effective removal of ⁹⁹TcO₄^-/ReO₄^- from contaminated water. Notably, CPN-3 marks a record-high adsorption capacity of 1052 mg/g for ReO₄^- after treatment with 1 M NaOH aqueous solutions for 24 h and demonstrates a rapid removal rate for ⁹⁹TcO₄^- from simulated Hanford and Savannah River Site waste streams. The mechanisms for the superior alkaline stability and ⁹⁹TcO₄^- capture performances of CPN-3 are investigated through combined experimental and computational studies. This work suggests an alternative perspective for designing functional materials to address nuclear waste management.