Schiff Base Cationic Covalent Organic Polymers for Highly Effective Removal of ReO^-₄: a Chemical Analogue of ⁹⁹TcO^-₄

Highly remediation of TcO^-₄ from used nuclear fuel reprocessing and radioactive environmental governance is of great significance for its high fission yield, environmental mobility and long half-life. Only a handful of materials can extract TcO^-₄ from aqueous solution and solid sorbent materials with fast kinetics and acid tolerance are still highly desirable. Herein, two cationic covalent organic polymers (BPA-TAB-Cl and BPA-TAE-Cl) was synthesized for the extraction of ReO^-₄, a non-radioactive chemical analogue of TcO^-₄. Both materials exhibit ultra-fast adsorption kinetics and almost quantitative ReO^-₄ can be removed within 20 s. In pH=2 water solution, the extraction capability is not obviously affected. Even in 100-fold exceed NO^-₄ solution, both cationic networks can capture 84% and 79% of ReO^-₄ respectively, indicating the excellent adsorption selectivity. After four sorption-desorption cycles, the adsorption capabilities have no obvious change. Finally, investigations of mechanism undoubtedly indicate that ReO^-₄ exists in both materials after anion exchange. Our results display bright prospect to eliminate radioactive contaminants by porous organic polymers.