Facile assembly and enhanced visible-light-driven photocatalytic activity of S-scheme BiOBr/g-C3N4 heterojunction for degrading xanthate in wastewater

The S-scheme BiOBr/g-C3N4 heterostructure composites with varying mass ratios were synthesized via a simple hydrothermal route. Compared to bare BiOBr and g-C3N4, the BiOBr/g-C3N4-10% photocatalyst performed the significantly enhanced photodegradation activity for ethyl xanthate in mineral flotation wastewater under visible light and possessed superior reusability as demonstrated by the reuse test. The degradation efficiency of BiOBr/g-C3N4-10% composite towards ethyl xanthate was up to 96.1% in 120 min, and its reaction rate constant was equal to about 6.3 times and 24.6 times that of bare BiOBr and g-C3N4, respectively. The improved visible-light-driven photodegradation activity was mainly attributed to the construction of S-scheme BiOBr/g-C3N4 heterojunction resulting in the effective separation of carriers. The results showed that superoxide radical (•O2–) played a dominant role in the degradation reaction. Furthermore, the carrier transfer mode in the S-scheme heterojunction and possible xanthate degradation mechanism was proposed. This paper provides a new idea for preparing S-scheme heterojunction and the construction of a high-efficiency photocatalytic system.