Study on the performance and mechanism of photocatalytic reduction of Cr(VI) through boron-doped g-C3N4 under visible light

Abstract

Hexavalent chromium (Cr(VI)) is an extremely toxic and soluble substance that poses a significant threat to human and environmental health. Photocatalysis is an efficient and environmentally friendly technique of reducing Cr(VI) in water. In this study, B-doped g-C₃N₄ (BCN) materials were synthesized by one-pot thermal polycondensation method. The experimental results indicated that under the visible light irradiation of citric acid solution, the photoreduction rate constant of BCN 1:0.15 for Cr(VI) reached 4.1421 h⁻¹, which was 7.15 times higher than that of g-C₃N₄, and 98.8 % of Cr(VI) could be degraded within 30 min. The electronic energy band structure and photocatalytic properties of BCN can be effectively tuned by adjusting the doping amount of boric acid. The B atoms were doped into the g-C₃N₄ lattice, replacing carbon atoms, while the BCN maintained the essential structure of g-C₃N₄. Compared with g-C₃N₄, the modified BCN exhibited a broader visible light response range and enhanced electron-hole separation capability. The stability and recyclability of the BCN photocatalysts were also evaluated. The results indicate BCN 1:0.15 maintained a high activity after five cycling experiments. In addition, a possible photocatalytic reduction mechanism was proposed based on free radical trapping experiments. This study provides insights and considerations for efficient photocatalytic reduction of Cr(VI) in wastewater.