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

Herein, sodium percarbonate (SPC), an effective and environment-friendly oxidant, was activated by ozone (O-3) for promoting elimination of sulfamethoxazole (SMX) in water. The effect of various parameters including SPC dosage, O-3 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 O-3 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 O-1 played an important role during SMX decomposition. SPC addition could promote (OH)-O-center dot production in O-3 system. The comparison of active species in different reaction system suggested that (OH)-O-center dot and O-center dot(2)- also play crucial role for SMX elimination. TOC and COD removal were all enhanced after 30 min treatment in O-3/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).

Automated summary

The combination of sodium percarbonate (SPC) and ozone (O-3) was effective in enhancing the elimination of sulfamethoxazole (SMX) in water, with alkaline conditions showing the best removal efficiency. Free radicals, especially (OH)•, played a crucial role in the decomposition of SMX, and the addition of SPC promoted the production of (OH)• in the O-3 system, leading to improved elimination of SMX. The degradation of SMX and the enhancement of TOC and COD removal were observed in the O-3/SPC system, indicating the potential of this method for water treatment.