Removal of gatifloxacin by activated peroxymonosulfate using co-pyrolysis materials of water treatment residuals and biomass: Nonradical-dominated mechanisms enhanced by adsorption

Abstract

Magnetic porous biochar derived from water treatment residuals and corn stalk (WTR-CS) was prepared by one-step pyrolysis method and applied for peroxymonosulfate (PMS) activation for gatifloxacin (GAT) removal. The results demonstrated that the adsorption and degradation efficiency of the WTR-CS/PMS system increased with the increasing pyrolysis temperature by changing their porosity, iron species and carbon configurations. WTR-CS obtained at 1000 °C (WTR–CS–1000) exhibited the best GAT removal effect, slight Fe leaching, strong stability and reusability. About 42.77% of GAT (40 mg L−1) was removed in the adsorption phase and 95.12% in total (90 min), accompanied by a 77% reduction in total organic carbon (TOC). The kinetic analysis demonstrated that adsorption was a key step in the overall catalytic process. Based on the quenching experiments, ESR and electrochemical tests, free radicals (SO4•-, ·OH and O2•-) and nonradical (1O2 and electron transfer) pathways jointly acted in the reaction, and nonradical pathway was dominant in the reaction. Four degradation pathways were proposed based on the intermediates detected by LC-MS, and the eco-toxicity of degradation intermediates was predicted by ECOSAR program. This study provides a new strategy for simultaneous iron-containing WTRs resource utilization and pollutant removal by synergistic adsorption and oxidative degradation.