Recycling 99 Tc From Nuclear Wastewater by Coupling Photocatalysis and In Situ Ion‐Exchange on Bifunctional K‐SnS/TiO 2 Heterojunction

ABSTRACT The sustainable management of radionuclides in nuclear wastewater, typically like 99 TcO 4 − resulting from 238 U 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/TiO 2 heterojunction. The photocatalytic reduction with in situ ion‐exchange converted mobile 99 TcO 4 − into immobilized 99 Tc 3+ . HCOOH‐assisted photocatalysis by generating ·CO 2 − radicals on TiO 2 , thus driving rapid 99 TcO 4 − reduction. Simultaneously, layered K‐SnS captured 99 Tc 3+ via in situ ion‐exchange with the K + in the framework, thereby forming stable coordination environments that inhibited the re‐oxidation of 99 Tc 3+ to soluble 99 TcO 4 − . Finally, the 99 Tc 3+ 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 99 Tc 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.