Activation of peroxymonosulfate by biochar in-situ enriched with cobalt tungstate and cobalt: Insights into the role of rich oxygen vacancies and catalytic mechanism

Abstract

The development of low-cost, stable, and recyclable multiphase catalysts in advanced oxidation process is essential for efficient degradation of antibiotics. In this study, a BC-Co-W-700 catalyst was used to activate peroxymonosulfate (PMS) for chlortetracycline (CTC) degradation. The catalyst was prepared using reclaimed biomass material as a matrix. The biochar-based catalyst possessed abundant active sites and realized the in-situ growth of Co and CoWO4. The BC-Co-W-700/PMS achieved 100% degradation of CTC (20 mg/L) within 18 min. Quenching and electron paramagnetic resonance experiments were conducted to investigate the reactive oxygen species (ROS) in the BC-Co-W-700/PMS system. The identified ROS in this system included 1O2, O2−, SO4−, and OH. Abundant ROS endowed the system with strong degradation performance, applicability, and anti-interference ability. The catalytic mechanism of BC-Co-W-700/PMS system was comprehensively investigated using a combination of electrochemical experiments and theoretical calculations. The in-situ pyrrolic N formed by biochar had a strong adsorption capacity for CTC, allowing pollutants to quickly adsorb to the catalyst surface. This greatly shortened the distance required for the catalytic reaction. The introduction of W led to abundant oxygen vacancies on BC-Co-W-700, causing the catalyst to produce a large amount of 1O2. Furthermore, the oxygen vacancies provided a high concentration of electrons for the conversion of Co3+/Co2+. In addition, CTC degradation pathways were analyzed using density functional theory calculations, and the toxicity of the intermediates was evaluated using the quantitative structure–activity relationship combined with experiments. The green catalyst synthesis method proposed in this paper could provide a new approach for the efficient degradation of antibiotics in wastewater.