Insights into electrocatalytic oxidation of aqueous ampicillin: Degradation mechanism and potential toxicity from intermediates

The residual antibiotics in environmental media posed a serious threat to public health and the ecosystem. In this work, the electrocatalytic degradation of ampicillin (AMP) by carbon nanotubes/agarose/titanium (CNTs/AG/Ti) electrode was studied and several experimental factors were further optimized. The results showed that the electrocatalytic degradation of AMP was highly dependent on applied potential and CNTs dosage. Under the optimal conditions (5 mg/L AMP, pH 8, 8 V applied potential, and 7 wt% CNTs dosage), the maximum degradation efficiency achieved 96.7% within 30 min. In the degradation process, superoxide radicals (•O2-) and hydroxyl radicals (•OH) played dominant roles, and the possible electrocatalytic degradation pathways for AMP were also proposed from the identified intermediates. Based on the quantitative structure-activity relationship (QSAR) model, the potential acute and chronic toxicities were predicted by the ecological structure-activity relationships (ECOSAR) program, and the bioconcentration factors (BCFs), developmental toxicity, and Ames mutagenicity were further analyzed using the toxicity estimation software tool (TEST). The results revealed the potential toxicity of some intermediates was higher than that of the parent antibiotic. This study provided an eco-friendly electrocatalytic technology for antibiotic wastewater treatment and investigated the potential toxicity of intermediates during the degradation process.