TiO/g-CN for Visible Light Photocatalytic Oxidation of Hypophosphite: Effect of Mass Ratio of TiO/g-CN.

Hypophosphite wastewater treatment is still a critical issue in metallurgical processes and the oxidation of hypophosphite to phosphate followed by the precipitation of phosphate is an important strategy for hypophosphite wastewater treatment. Herein, TiO/g-CN photocatalysts with various mass ratios (TiO (m): g-CN (m) = 0.5, 0.2, 0.1, and 0.05) were synthesized by a hydrolysis method and the effect of the mass ratio of TiO (m): g-CN (m) on TiO/g-CN visible light photocatalytic oxidation of hypophosphite was evaluated. The as-prepared TiO/g-CN were characterized and confirmed by SEM, XPS, XRD and FTIR. Moreover, the specific surface area and the distribution of pore size of TiO/g-CN was also analyzed. Our results showed that TiO/g-CN exhibited remarkably improved photocatalytic performance on hypophosphite oxidation compared with g-CN and meanwhile 1:2-TiO/g-CN with a mass ratio of 0.5 showed the best photocatalytic performance with the highest oxidation rate constant (17.7-fold and 91.0-fold higher than that of pure g-CN and TiO, respectively). The enhanced performance of photocatalytic oxidation of hypophosphite was ascribed to the heterojunction structure of TiO/g-CN with broader light absorption and significantly enhanced efficiency of the charge carrier (e-h) generation and separation. Additionally, the generated ·OH and · radicals contributed to the hypophosphite oxidation during the photocatalytic system.