Electrochemical degradation of doxycycline in a three-dimensional vermiculite/peroxymonosulfate electrode system: Mechanism, kinetics, and degradation pathway

In this study, vermiculite (VER) powder was used as a particle electrode in a three-dimensional (3D) Ti-IrO2/Ta2O5 electrode system for the electrochemical degradation of doxycycline (DOX) combined with peroxymonosulfate (PMS) activation. The effects of operational parameters (such as VER dosage, PMS concentration, initial pH, and current density) on DOX degradation were studied and the optimal parameters were discussed. Electrochemical degradation and electrochemical analysis showed that the addition of VER particles could improve the electrochemical conversion efficiency of the 3D electrochemical system by increasing the oxygen evolution potential and inhibiting the occurrence of oxygen evolution side reactions. Quenching experiments showed that sulfate free radicals are the leading reactive oxygen species in the system. A possible pathway for DOX degradation by the reaction system was proposed based on intermediates detected using liquid chromatography–electrospray ionization–quadrupole–time of flight (LC–ESI–Q–TOF). The toxicity of all the intermediates was predicted using the ECOSAR program. Our study showed that the 3D VER/PMS electrode system was reliable for repairing surface water or groundwater polluted by antibiotics.