Insights into the electrochemical degradation of sulfamethoxazole and its metabolite by Ti/SnO_(2)-Sb/Er-PbO_(2) anode

Electrochemical degradation of sulfamethoxazole(SMX)and its metabolite acetyl-sulfamethoxazole(AcSMX)by Ti/SnO_(2)-Sb/Er-PbO_(2) were investigated.Results indicated that the electrochemical degradation of SMX and Ac-SMX followed pseudo-first-order kinetics.The rate constants of SMX and Ac-SMX were 0.268 and 0.072 min-1 at optimal curre nt density of 10 and 14 mA/cm^(2),respectively.Transformation products of SMX and Ac-SMX were identified and the possible degradation pathways,including the cleavage of S-N bond,opening ring of isoxazole and nitration of amino group,were proposed.Total organic carbon removal of SMX was nearly 63.2%after 3 h electrochemical degradation.22.4%nitrogen of SMX was trans formed to NO_(3)-,and 98.8%sulfur of SMX was released as SO_(4)2-.According to quantitative structureactivity relationship model,toxicities of SMX and Ac-SMX to aquatic organisms significantly decreased after electrochemical degradation.Electric energy consumption for 90%SMX and Ac-SMX degradation was determined to be 0.58-8.97 and 6.88-44.19 Wh/L at different experimental conditions,respectively.Compared with parent compound SMX,the metabolite Ac-SMX is more refractory and toxic,which emphasizes the importance of taking its metabolites into account when investigating the disposal of pharmaceuticals from wastewater.