Metal chalcogenides as ion-exchange materials for the efficient removal of key radionuclides: A review

The large amount of radioactive waste generated by the rapid development of nuclear energy is in urgent need of disposal. Metal chalcogenide ion-exchangers (MCIEs) are newly developed in recent years that show great potential in the field of removing radionuclides. This is a comprehensive review of the latest research progress on the removal of key radioactive ions (e.g., radioactive Cs+, Sr2+, UO22+, lanthanide ions, and actinide ions) by MCIEs. The structure and ion-exchange properties of MCIEs are summarized emphatically. The ion-exchange mechanism of MCIEs is discussed and the structure-function relationship is preliminarily revealed. Easily exchangeable cations in the interlayer/channel, appropriately sized interlayer/channel/window spaces, flexible open framework, and the strong affinity of the Lewis soft base S2−/Se2− sites in the framework for soft or relatively soft metal ions, are the keys to the excellent selectivity and fast adsorption kinetics of MCIEs for radioactive ions. Finally, future research directions of metal chalcogenides for radioactive ions removal are foreseen. It is hoped that the review will provide a reference for the design of new metal chalcogenide ion-exchangers with practical application prospects for radioactive waste treatment and point to new directions for environmental radioactive contamination control.