K doped defective g-C3N4 decorated with cyano group for boosting visible-light driven photocatalytic removal of uranium

Utilizing elemental doping and defect engineering are effective means to enhance the efficiency of g-C3N4 materials for photocatalytic removal of uranium. In this investigation, we synthesized a defective g-C3N4 photocatalyst co-decorated with K+ doping and cyano groups (KHCN) through a straightforward one-step alkali etching process. The alkali etching not only enhances the specific surface area to improve the adsorption of uranium by KHCN but also significantly accelerates the photocatalytic removal of uranium through the introduction of K+ and cyano groups. The KHCN can almost completely remove 40 mg/L of U(VI) under air and visible LED light irradiation (pH 5.0, 298.15 K). Notably, the photocatalytic removal of U(VI) by KHCN demonstrated excellent selectivity and reusability. The mechanism studies reveal that alkali etching-induced introduction of K+ ions and cyano groups enhances visible light absorption, strengthens the efficiency of photogenerated carrier separation, and reduces the band gap. The activation of U(VI) in solution primarily occurs through photogenerated e- and O2–, subsequently immobilizing as metastudtite ((UO2)O2·2H2O). This study provides a viable approach for synthesizing highly efficient photocatalytic materials for uranium removal, leveraging synergistic doping and defect engineering.