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Degradation of aqueous cefotaxime in electro-oxidation — electro-Fenton —persulfate system with Ti/CNT/SnO2–Sb–Er anode and Ni@NCNT cathode

Jiawei Lei,Pingzhou Duan,Weijun Liu,Zhirong Sun,Xiang Hu

Due to the potential threatening of antibiotics in aqueous environment, a novel electro-oxidation (EO) — electro-Fenton (EF) —persulfate (PS) system with the addition of peroxydisulfate and Fe 2+ was installed for the degradation of cefotaxime. Ti/CNT/SnO 2 –Sb–Er with an ultra-high oxygen evolution potential (2.15 V) and enhanced electrocatalytic surface area was adopted as anode. The OH production and electrode stability test demonstrated great improvement in the electrochemical performances. Ni@NCNT cathode was tested with higher H 2 O 2 generation by the presence of nitrogen functionalities due to the acceleration of electron transfer of O 2 reduction. Experiment results indicated CNT and ErO 2 modification increased the molecular and TOC removal of cefotaxime. Coupling processes of EO-EF and EO-PS both resulted in shorter electrolysis time for complete cefotaxime removal, however, the mineralization ability of EO-PS process was lower than EO-EF, which might result from the immediate vanishing of PS. Thus, a further improved treatment EO-EF-PS system achieved an 81.6% TOC removal towards 50 mg L −1 cefotaxime after 4 h electrolysis, under the optimal working condition Fe 2+  = PS = 1 mM. The influence of current density and initial concentration on the performance of all processes was assessed. Methanol and tert-butanol were added in the system as OH and SO 4 − scavengers, which illustrating the mechanism of EO-EF-PS oxidizing process was the result of the two free radicals. Major intermediates were deduced and the degradation pathway of cefotaxime was analyzed. This research provides a potential coupling process with high antibiotic removal efficiency and effective materials for practical uses.