Recycling 99Tc From Nuclear Wastewater by Coupling Photocatalysis and In Situ Ion-Exchange on Bifunctional K-SnS/TiO2 Heterojunction.

The sustainable management of radionuclides in nuclear wastewater, typically like 99TcO4 - resulting from 238U fission, is limited by their high mobility, long half-lives and redox sensitivity. Herein, we developed a photocatalysis-ion-exchange coupling strategy for closed-loop removal and recycling of radioactive metal in nuclear wastewater based on a novel bifunctional K-SnS/TiO2 heterojunction. The photocatalytic reduction with in situ ion-exchange converted mobile 99TcO4 - into immobilized 99Tc3+. HCOOH-assisted photocatalysis by generating ·CO2 - radicals on TiO2, thus driving rapid 99TcO4 - reduction. Simultaneously, layered K-SnS captured 99Tc3+ via in situ ion-exchange with the K+ in the framework, thereby forming stable coordination environments that inhibited the re-oxidation of 99Tc3+ to soluble 99TcO4 -. Finally, the 99Tc3+ could be recycled by reverse ion-exchange in concentrated KCl solution. This coupled electron-ion transfer established a dynamic interfacial mechanism that linked redox transformation with structural confinement. The system achieves efficient 99Tc removal across diverse aqueous chemistries, including high ionic strength conditions, and enables complete recovery through reverse ion-exchange. Our results provide a generalizable route for integrating the transformation, immobilization, and recovery of redox-active contaminants, thereby advancing sustainable nuclear wastewater management.