Pyrite/biochar-activated peroxymonosulfate strengthens tetracycline degradation: Important roles of surface functional groups and Fe(Ⅱ)/Fe(Ⅲ) redox cycling

Abstract

Nonradical species with high anti-interfering properties have shown significant advantages in complex wastewater treatment. Herein, a pyrite/biochar catalyst (FBC) was prepared using pine sawdust biochar (BC) as a support material loaded with pyrite (FeS2). It exhibited high activity and stability in the FBC/PMS system for effective activation of peroxymonosulfate (PMS) to degrade tetracycline (TC) over a wide pH range (3.0–9.0). According to the characterization and analysis data, a variety of oxygen-containing functional groups (CO, -OH) and Fe and S active sites on the FBC surface assisted in PMS decomposition to produce reactive oxygen species (ROS). The mechanism study showed that the redox cycling of Fe(Ⅱ)/Fe(Ⅲ) and the electron-transfer medium of the BC oxygen functional groups contributed to the formation of SO4•-, •OH, O2•-, 1O2 and FeⅣ=O, but 1O2 was the main active oxidant. The potential pathways for TC degradation were suggested, and the toxicity of by-products was predicted by toxicity evaluation. Furthermore, FBC/PMS system exhibited minimal sensitivity to interference of concomitant materials. Overall, this study provided a reference for the application of green advanced oxidation technology of iron-based mineral composites to treat pharmaceutical contaminants in real water.