Selective Sequestration of Perrhenate by Cationic Polymeric Networks Based on Elongated Pyridyl Ligands

Effective elimination of pertechnetate (TcO4–) from nuclear waste is meaningful for decreasing the impact toward actinide separation and reducing the amount of radioactive wastewater from disposal nuclear waste. Nevertheless, construction of sorbents with the features of facile synthesis, strong acid and alkali resistance, fast sorption kinetics, and high sorption capacity remains quite challenging. In this work, cationic polymeric networks (CPN-X1-Cl and CPN-X2-Cl) based on elongated organic ligands were designed and synthesized by a facile quaternization reaction, and their sorption performance toward ReO4– was thoroughly investigated. The plentiful pyridinium moieties endowed these cationic polymer networks with high charge density, resulting in CPN-X1-Cl achieving a maximum sorption capacity of 813 mg/g and surpassing most cationic materials. Furthermore, both CPN-X1-Cl and CPN-X2-Cl exhibited ultrafast sorption kinetics, high selectivity, and recyclability in five recycles. The sorption mechanism was clearly elucidated by XPS, FT-IR, ion chromatography, and DFT calculations, revealing the process of anion exchange, sorption geometry, and binding energy. In addition, in the dynamic sorption experiments, CPN-X1-Cl as a filler could effectively remove ReO4–, showing impressive practical application ability in disposal of radioactive waste. This work indicated that the CPNs with elongated ethynyl-based ligands had tremendous potential as radioactive TcO4– scavengers.