Electro-oxidation of ceftazidime in real municipal wastewater using PbO2–Ce and SnO2–Sb electrodes: influence of electrolyte and degradation pathway

Abstract

Ceftazidime was selected as target pollutant for electrochemical degradation on two most typical dimensional stable anodes Ti/PbO2–Ce and Ti/SnO2–Sb due to its broad persistence in environment. Degradation experiments were conducted through spiking 5 mg L−1 ceftazidime in real secondary effluents and evaluating the residual antibiotics or COD after 1 h and 4 h electrolysis, respectively. The morphology, composition and electrochemical characteristics of the anodes were compared and it was demonstrated that Ti/SnO2–Sb performed the highest degradation rate because of its superior hydroxyl (·OH) production capability and Ti/PbO2–Ce was regarded as the most stable anode proved by stability tests in 0.5 M aqueous H2SO4 with an anodic current density of 1.0 A. As high as 99.37% of ceftazidime degradation and 95.52% COD removal was achieved on Ti/SnO2–Sb anode under a current of 4 mA cm−1, compared with 75.15% ceftazidime degradation and 83.54% COD removal on Ti/PbO2–Ce. The effects of NaCl and humic acid (HA) in electrolyte were mainly investigated because their existence could interfere the electrochemical degradation process. The experiment results showed NaCl concentration can significantly enhance the oxidation rate with 99% removal within 5 min of treatment on Ti/SnO2–Sb anode, while humic acid concentration is a parameter that inhibited electrochemical catalyzing. Therefore, the degradation efficiency of spiked ceftazidime in real wastewater was evaluated. The last lead to the identification of intermediates during 150 min degradation process and a pathway scheme of ceftazidime was proposed.