CdS@NiCr-LDH Z-scheme heterojunction with high adsorption–photocatalysis for uranium(VI) removal without any sacrificial agent

The use of photocatalysis for the removal of U(VI) has the advantages of being green, eco-friendly and sustainable. It is common practice to enhance the photocatalytic activity of photocatalysts by adding sacrificial agents, however, this is uneconomical and contrary to the vision of carbon neutrality and carbon peak in the world. Herein, we fabricate a Z-scheme heterojunction for the photocatalytic removal of uranium (VI) based on CdS nanorods@NiCr layered double hydroxide (CdS@NiCr-LDH). Excellent photocatalytic efficiencies and removals were achieved under visible light irradiation without any sacrificial agent. The optimum uranium(VI) removal rate of CdS@NiCr-LDH was 0.057 min-1, which was 6.3 and 5.0 times higher than that of CdS and NiCr-LDH, respectively. In particular, the U(VI) removal amount over CdS@NiCr-LDH reached 2246.14 mg g-1. The CdS@NiCr-LDH heterojunction creates a narrower energy band gap (Eg=2.06 eV), which is more favorable for visible light absorption, according to UV-vis DRS results. According to ESR and DFT calculations, possesses an intrinsic electric field between NiCr-LDH and CdS composite that efficiently prevents electron-hole complexation, resulting in highly efficient removal of U(VI) under visible light irradiation without the need of sacrificial agents. This work lays the foundation for research on photocatalytic U(VI) treatment by CdS@NiCr-LDH in wastewater.