Electrochemical removal of antibiotics and multi-drug resistant bacteria using S-functionalized graphene sponge electrodes

Abstract

In this study, we synthesized S-functionalized graphene sponge electrode and applied it for electrochemical oxidation of five commonly used antibiotics, namely sulfamethoxazole, trimethoprim, ofloxacin, roxithromycin and erythromycin, and the inactivation of a multi-drug resistant Escherichia coli (E. coli). The experiments were performed using real drinking water in a flow-through, one-pass mode. Highly polar antibiotics such as sulfamethoxazole did not adsorb onto the graphene sponge but were completely removed (i.e., ≥95% removal) at low applied current densities (14.5 A m−2). Antibiotics with high affinity for π-π interactions such as ofloxacin were completely removed already in the open circuit, and current application led to their further degradation. S-doped graphene sponge anode resulted in 4.5 log removal of a multi-drug resistant E. coli at 29 A m−2. There was no regrowth of bacteria observed during storage of the electrochemically treated samples, suggesting that the treatment severely impacted the cell viability. Further E. coli removal of 0.7 log was observed after the storage of electrochemically treated samples. The energy consumption of a continuously operated electrochemical system that achieved 4.5 log inactivation of a multi-drug resistant E. coli and 87–99% removal of antibiotics was 1.1 kWh m−3.