Enhancement of U(VI) removal by g-C3N4/HAP composites via adsorption and solar driven photocatalysis synergy

The combination of adsorption and photocatalysis offers a synergistic strategy for enhanced U(VI) removal. In this study, g-C 3 N 4 /HAP composites were synthesized via a hydrothermal method to achieve efficient U(VI) removal. Hydroxyapatite (HAP) provides abundant adsorption sites for rapid U(VI) enrichment, while graphitic carbon nitride (g-C 3 N 4 ) exhibits excellent visible-light response, enabling the photocatalytic reduction of U(VI) to U(IV). The heterojunction formed between HAP and g-C 3 N 4 effectively suppresses electron-hole recombination, facilitating electron transfer and narrowing the band gap. Characterization revealed that the composite achieved a U(VI) removal efficiency of 99.28 % and a maximum adsorption capacity of 4880.95 mg/g, 1.85 times higher than single-component systems. Under solar light, photogenerated electrons in g-C 3 N 4 reduce U(VI) via interaction with dissolved oxygen to form superoxide radicals (· O 2 − ). This synergistic mechanism enhances photocatalytic performance and adsorption efficiency. The material exhibited excellent stability over multiple cycles, demonstrating its practical potential for environmental remediation. This study highlights the g-C 3 N 4 /HAP composite as a promising solar-driven material for efficient U(VI) removal, providing a sustainable and effective solution for uranium-contaminated water treatment.