Behaviour of multi-component mixtures of tetracyclines when degraded by photoelectrocatalytic and electrocatalytic technologies

The main objective of this work was to study and contrast the degradation behaviour of multi-component mixtures of tetracyclines (TCs) during processes of the photoelectrocatalysis (PEC) and electrocatalysis (EC). During these two processes, we investigated the degradation efficiency of TCs under different influence factors and their reaction mechanisms and degradation kinetics, and the degradation difference of TC, oxytetracycline (OTC) and chlortetracycline (CTC). The results indicate that applied bias potentials, pH and reaction atmosphere greatly influenced the degradation of TCs. Under different pH conditions, the degradation efficiency of TC and OTC changed little, but that of CTC varied greatly. This difference may stem from the halogen group (-Cl) that CTC carries. Under given conditions, PEC generated greater photocurrent, and the degradation efficiency during the PEC process was higher by about 10% at 180 min. The manners in which HO center dot radicals were generated during the PEC and EC processes were also compared. TCs degradation in the two processes accorded well with the first-order reaction kinetics equation at lower bias potentials, whereas at a higher bias potential of 2 V, both reactions deviated from the equation, and their fitting curves were closer to parabolic.