Insights into the pathways, intermediates, influence factors and toxicological properties in the degradation of tetracycline by TiO2-based photocatalysts

A large amount of CO2 was produced every year due to the mineralization of antibiotics, which undoubtedly accelerated the arrival of carbon emission peaks. If complete mineralization can be avoided during the photodegradation, and instead the reaction can be directed towards the production of usable intermediates and their utilization, it can undoubtedly achieve excellent effluent resource utilization while simultaneously reducing carbon. By classifying the photodegradation pathway of tetracycline (TC) in conjunction with oxytetracycline (OTC) and doxycycline (DC) by TiO2-based photocatalysts, we focus our discussion on the representative intermediate products generated during the process of photodegradation. In addition, we systematically summarized the transformation relationships among these intermediates. Furthermore, we investigated the influencing factors (such as pH, inorganic ions, light, and humic acid) of intermediates generation and transformation during the photodegradation of TC. The environmental toxicity of typical intermediates of TC photodegradation was discussed here. Finally, we proposed the concept of photocatalytic process modulation, and have foreseen the possibility of utilizing intermediates to achieve effluent resource utilization.