Enhanced photocatalytic activity of g-C3N4/TiO2 heterojunction for uranium extraction from seawater

Uranium (U) pollution, characterized by its radiotoxicity, poses severe threats to environmental safety. Photocatalytic technology has garnered increasing attention for treating U-containing wastewater due to its high efficiency, ease of operation, and absence of secondary pollution. However, photocatalytic materials currently used for U extraction suffer from poor stability, weak resistance to salt ion interference, and high recombination rates of photogenerated carriers, limiting their applicability in complex environments, such as seawater. To tackle these challenges, we have innovatively designed a direct Z -scheme heterojunction photocatalyst, combining carbon nitride doped with oxygen and phosphorus (C 3 N 4 (OP)) with titanium dioxide (TiO 2 ). Here, doping with oxygen and phosphorus, along with the formation of a heterojunction, were employed to modulate the bandgap, enhance visible light absorption, and promote charge separation through an internal electric field. Experimental results demonstrated that the TiO 2 /C 3 N 4 (OP) system achieved a Uremoval efficiency exceeding 85 % under visible light irradiation, while maintaining structural stability and salt ion resistance in simulated seawater. Density Functional Theory (DFT) calculations revealed a directional electric field formation mechanism at the TiO 2 /C 3 N 4 (OP) interface, confirming that superoxide radicals (•O 2 − ) are the dominant active species, with hydroxyl radicals (•OH) serving as auxiliary contributors. This work establishes a synergistic mechanism involving bandgap engineering, interfacial charge separation, and active species collaboration, offering a novel strategy for solar-driven remediation of radioactive pollutants in complex environments.