Electrochemical activation of peroxymonosulfate at Ti/La2O3-PbO2 anode to enhance the degradation of typical antibiotic wastewater

In this study, a novel electrochemically anodic activated peroxymonosulfate (PMS) system ((Ti/La2O3-PbO2)EA-PMS) was constructed by combining the Ti/La2O3-PbO2 anode with PMS. The prepared (Ti/La2O3-PbO2)EA-PMS system removed 98.07% of cefadroxil (CFR), which was 17.85% higher than that of the single electrochemical (EC) system and 78.10 % higher than that of the PMS system. In addition, the (Ti/La2O3-PbO2)EA-PMS system showed the satisfactory applicability to the single and mixed wastewater of CFR, tetracycline (TC), and levofloxacin (LFX) with the degradation rate greater than ~95%, the stability and degradation performance was much better than the conventional PMS activation systems. The excellent degradation performance was partially attributed to the excellent physico-chemical and electrochemical performances of Ti/La2O3-PbO2 anode, such as the rougher and compact surface, faster mass and electron transfer performance, the higher proportion of the adsorbed hydroxyl oxygen (Oads) for the production of reactive oxygen species (ROS) and a higher oxygen evolution overpotential to inhibit the occurrence of the electrolysis of water. In addition, the collaboration of Ti/La2O3-PbO2 anode and PMS activation produced a synergistic effect on the degradation of antibiotics, which mainly reflected at the direct-electron-transfer controlled non-free radical oxidation occurred on the surface of Ti/La2O3-PbO2 anode and the free radical oxidation dominated by adsorbed OH (PbO2(OH)), free hydroxyl radical (OH) and sulfate radical (SO4−). Moreover, the effects of operating parameters (PMS concentration, current density and initial pH value) and water background components on the removal of CFR by (Ti/La2O3-PbO2)EA-PMS system were investigated. The possible degradation pathways of CFR were also speculated. The electrochemically anodic activated PMS system based on Ti/La2O3-PbO2 anode was expected to provide an efficient technology for the treatment of actual pharmaceutical wastewater and this work also provided a significant reference for the design of novel advanced oxidation process combined with PMS (AOP-PMS) systems.