Electrochemical activation of peroxymonosulfate (PMS) by carbon cloth anode for sulfamethoxazole degradation

Electrochemical activation of peroxymonosulfate (PMS) at carbon cloth anode (E (Carbon cloth Anode)/PMS system) was investigated for sulfamethoxazole (SMX) degradation. The results indicated that PMS could be activated at carbon cloth anode during electrolysis, resulting in the improvement of SMX degradation. The degradation efficiency of SMX was facilitated with the higher PMS concentration and current density, respectively. The degradation rate constant of SMX increased with the rising pH from 3.6 to 6.0, and reached the highest value at pH 6.0, and then decreased with further increasing pH to 8.0. The presence of chloride ion (Cl^-, 5-100 mM) significantly enhanced SMX degradation, while addition of humic acid (HA, 1-5 mgC L^-1) inhibited SMX degradation. Addition of carbonate (HCO₃^-, 5-20 mM) had a negligible impact on SMX degradation. Small amounts of phosphate (PO₄^3-, 0-5 mM) could promote degradation, while a large amount of PO₄^3- (10-20 mM) inhibited the degradation. Moreover, the quenching experiments demonstrated that sulfate radical (SO₄·^-), hydroxyl radical (·OH) and singlet oxygen (¹O₂) contributed to SMX degradation in E (Carbon cloth Anode)/PMS system. The degradation intermediates of SMX were identified by LC-MS/MS and the degradation pathways were deduced to be hydroxylation, the cleavage of S-N bond, and oxidation of aniline group. Moreover, the micronucleus test of Vicia faba root tips indicated that the E (Carbon Cloth Anode)/PMS system could reduce the genetic toxicity of SMX contaminated water to some extent.