Study on preparation, photocatalytic performance and degradation mechanism of Bi2WO6/Bi2S3/g-C3N4 composite

Abstract

A new lotus-like Bi₂WO₆/Bi₂S₃/g-C₃N₄ composite was synthesized through hydrothermal reaction and physical doping techniques. And the degradation of norfloxacin (NFX) using Bi₂WO₆/Bi₂S₃/g-C₃N₄ (BiSW-GCN) photocatalytic material was investigated. Scanning electron microscopy (SEM) revealed that spherical Bi₂S₃ and flake-like g-C₃N₄ were closely adhered to the petals of Bi₂WO₆, with a uniform distribution of various elements observed in the Raman spectra. These spectra also indicated a reduction in fluorescence intensity and the recombination rate of photogenerated electron-hole pairs. Through analysis of the degradation efficiency of NFX with varying ratios of the photocatalytic materials, it was determined that the optimal photocatalytic performance was achieved when Bi₂S₃ constituted 3 % of the Bi₂WO₆ content, and the Bi₂WO₆/Bi₂S₃ to g-C₃N₄ ratio was set at 20:1. The influence of pH value, photocatalyst concentration, and NFX concentration on the degradation rate within the reaction environment was examined. Results showed that the material exhibited its highest efficiency in a neutral environment. With the addition of 1 g/L BiSW-GCN, the degradation rate of an 8 mg/L NFX solution reached 92.4 % within 120 min, and the total organic carbon (TOC) removal rate achieved 41.1 %. The kinetic constant for BiSW-GCN was calculated to be 0.0206 min⁻¹. A trapping experiment demonstrated that the primary toxicity of the photocatalytic process was due to hole action, followed by photoelectron generation. Based on the inhibitory effect of NFX on E. coli, the toxicity of the degraded NFX solution was found to be absent when analyzed using the product intermediate toxicity assessment method, thus confirming the potential for the by-product to be non-toxic.