Grape-like BiVO4@Bi2S3-BC heterojunction with rich sulphur vacancies promotes persulfate activation for highly efficient degradation of organic pollutants

Abstract

Developing cost-efficient and eco-friendly catalysts while comprehending their catalytic mechanisms in advanced oxidation processes that utilize persulfate (PS-AOPs) presents a significant challenge. In this paper, a simple hydrothermal-calcination process was used to generate a novel V_s-BiVO₄@Bi₂S₃-BC catalyst with excellent degradation of tetracycline (TC) (95.8 % degradation within 5 min). Results from the characterization indicate that the incorporation of carbon spheres (BC) enhances the dispersion, surface area, and electron transport properties of BiVO₄@Bi₂S₃. The newly developed V_s-BiVO₄@Bi₂S₃-BC demonstrated impressive performance in the degradation and mineralization of tetracycline (TC), achieving rates of 99.99 % and 93.81 %, respectively, within a span of just 35 min. This remarkable efficacy can be primarily attributed to the composite’s larger specific surface area, which allows for greater interaction with the target compound, as well as the presence of a higher number of active sites that facilitate the degradation process. Additionally, further investigations, including quenching experiments and electron spin resonance (EPR) analyses, identified that singlet oxygen (¹O₂) and superoxide anion (O₂•⁻) were the predominant reactive oxygen species involved in the degradation process. The sulphur vacancies were further confirmed as the main active sites by theoretical calculations. Meanwhile, a possible pathway for TC degradation was proposed and a reduction in the toxicity of the intermediates was observed. Moreover, a continuous stirred tank reactor (CSTR) was designed to demonstrate the effective performance of the 1.5BVOS-BC-PTFE/PMS system in continuous water treatment operation mode. This study provides a new insight into understanding the mechanism of persulfate activation in bismuth-based composites-biochar composites.