Efficient electrochemical oxidation of cephalosporin antibiotics by a highly active cerium doped PbO2 anode: Parameters optimization, kinetics and degradation pathways

Removing cephalosporin contaminants from aquatic environments is of great concern because of the hazards they pose to the environment and human health. In this study, a Ce-PbO2 anode with a SnO2-Sb intermediate layer was fabricated using an electrochemical deposition method and used for the electrocatalytic oxidation of cephalosporin antibiotics. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the successful preparation of the Ce-PbO2 anode and revealed that Ce doping resulted in a highly stable structure and crystallinity of the PbO2 crystals. Moreover, the Ce-PbO2 anode exhibited excellent electrochemical performance with higher oxygen evolution potential (1.56 V), larger electroactive surface area (1.104 C cm-2), smaller corrosion current density (1.796 x 10-4 A cm-2), and higher hydroxyl radical (& BULL;OH) yield (8.64 mM min-1 m-2) compared with the intermediate layer and PbO2 anode. The effects of major operating parameters, including current density (20-80 mA cm-2), electrolyte concentration (0.050-0.125 M), initial concentration of target compounds (5-75 mg L-1), and pH (2-10) on the removal efficiencies of cefradine (RAD), and cephalothin (CEP) at the Ce-PbO2 electrode were investigated. The research results illustrated that when electrolysis was carried out for 90 min at the optimal current density of 40 mA cm-2 , an initial concentration of 50 mg L-1 , and an electrolyte concentration of 0.10 M, the removal efficiency of RAD and CEP were higher than 99%. Additionally, the degradation process followed pseudo-first-order kinetics. The total organic carbon (TOC) removal efficiency of RAD and CEP was 60.6% and 68.2% after 240 min, respectively, under the optimal conditions. The energy consumption for RAD and CEP degradation was 1.74 and 3.04 kWh g-1 TOC, respectively. In addition, the Ce-PbO2 electrode exhibited good stability over nine consecutive cycles. Using UPLC-MS, the intermediate products of RAD and CEP were confirmed, and the degradation intermediates were completely oxidized to CO2 , H2O, and inorganic ions (SO42- , NO3-). During electrolysis, the intermediate toxicity was studied using Escherichia coli growth inhibition tests, and the growth inhibition rate was calculated. Considering these results, the Ce-PbO2 anode could be utilized to treat wastewater containing cephalosporin antibiotics with high efficiency.