Promoted elimination of antibiotic sulfamethoxazole in water using sodium percarbonate activated by ozone: Mechanism, degradation pathway and toxicity assessment

Abstract

Herein, sodium percarbonate (SPC), an effective and environment-friendly oxidant, was activated by ozone (O3) for promoting elimination of sulfamethoxazole (SMX) in water. The effect of various parameters including SPC dosage, O3 dosage, SPC concentration, pH value and radical scavenger on SPC elimination was investigated firstly. Results showed that with increase of SMX dosage, the removal efficiency of SMX firstly improved and then declined. With optimal SPC dosage of 0.2 g/L, the removal efficiency of SMX rose by 16.4%, and corresponding kinetic constant multiplied by 1.7 times. Improving O3 dosage and reducing SMX concentration were beneficial to SMX elimination. Compared with acidic and neutral conditions, alkaline condition was favorable for SMX elimination. Radical trapping experiment showed that 1O played an important role during SMX decomposition. SPC addition could promote OH production in O3 system. The comparison of active species in different reaction system suggested that OH and O2− also play crucial role for SMX elimination. TOC and COD removal were all enhanced after 30 min treatment in O3/SPC system. Degradation process of SMX was inspected via UV–Vis spectra, pH variation, conductivity variation and ammonia nitrogen variation. The degradation pathway was predicted by discrete Fourier transform (DFT) coupled with literatures. Finally, the toxicity of degradation intermediates was evaluated by US Environmental Protection Agency Toxicity Estimation Software Tool (US-EPA-TEST).