Degradation of the Common Aqueous Antibiotic Tetracycline using a Carbon Nanotube Electrochemical Filter

Abstract

In this work, a carbon nanotube (CNT) electrochemical filter was investigated for treatment of aqueous antibiotics using tetracycline (TC) as a model compound. Electrochemical filtration of 0.2 mM TC at a total cell potential of 2.5 V and a flow rate of 1.5 mL min(-1) (hydraulic residence time <2 s) resulted in an oxidative flux of 0.025 ± 0.001 mol h(-1) m(-2). Replacement of the perforated Ti cathode with a CNT cathode increased the TC oxidative flux by 2.3-fold to 0.020 ± 0.001 mol h(-1) m(-2) at a total cell potential of 1.0 V. Effluent analysis by liquid chromatography-mass spectrometry and disk agar biocidal diffusion tests indicate that the electrochemical filtration process can degrade the TC molecular structure and significantly decrease its antimicrobial activity, respectively. Addition of dissolved natural organic matter (NOM) negatively affected the TC electrooxidation because of competition for CNT sorption and electrooxidation sites. At 2.0 V total cell potential, TC spiked (0.2 mM) into drinking water reservoir and wastewater treatment plant effluent samples had an oxidative flux of 0.015 ± 0.001 and 0.022 ± 0.001 mol h(-1) m(-2), respectively, and an energy requirement of 0.7 kWh kgCOD(-1) or 0.084 kWh m(-3). These results indicate a CNT electrochemical filter may have potential to effectively and efficiently treat antibiotics in water and wastewater effluent.