Insight into the performance and mechanism of highly selective photocatalytic uranium extraction from solutions using C3N4/CdS heterojunction

The complexity of real-water environments urged us to explore efficient photocatalytic systems for U(VI) extraction, especially considering the robustness against variable environmental factors. Herein, a type II heterojunction was engineered by integrating ultrathin g-C 3 N 4 nanosheets and CdS nanoparticles (GCN-3CS) for visible-light-driven U(VI) extraction without sacrificial agent in both aerobic and O 2 -free environments. GCN-3CS demonstrated broad pH adaptability, achieving ~95 % of U(VI) removal efficiency after 120 min of illumination at pH 4.0, while revealing accelerated kinetics at pH 5.0–8.5 with over 95 % of U(VI) elimination reached within just 60 min of visible-light irradiation. The photocatalytic performance of GCN-3CS exhibited temperature dependence, achieving over 95 % of U(VI) removal within 30, 45, and 60 min at 50, 35, and 20 °C, respectively. GCN-3CS showed exceptional tolerance to high salinity (up to 1.0 M NaNO 3 ) and excellent anti-interference capability against various coexisting ions. The reusability and environmental adaptability of GCN-3CS were validated and attained the satisfied performance. Furthermore, mechanistic studies based on macroscopic experiments and spectral characterizations revealed that the extraction of U(VI) was controlled by photocatalytic reduction-oxidation under aerobic conditions and solely by photocatalytic reduction under O 2 -free conditions. This work advanced the design of ideal photocatalyst for U(VI) extraction from complex water environments and provided a feasible strategy for managing water radioactive contaminations through the tunable heterojunction engineering.