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.

Mineralization of organic pollutants by anodic oxidation using reactive electrochemical membrane synthesized from carbothermal reduction of TiO2

“…Recently, carbon nanotube electrochemical filters have been developed for the removal of organic pollutants, however they are not active for OH production (Tsierkezos and Ritter, 2012;Schnoor and Vecitis, 2013;Gao and Vecitis, 2013;Liu et al, 2015). Besides, research works from Guo et al (2016) showed that a convectionenhanced rate constant for Fe(CN) 6 4À oxidation of 1.4 10 À4 m s À1 e the highest reported in the literature, close to the kinetic limit e was reached by using porous sub-stoichiometric titanium oxide (TiO x ) reactive electrochemical membrane (REM) .…”

Activated Carbon, Carbon Nanotubes and Graphene: Materials and Composites for Advanced Water Purification

“…Interactions between the CNTs and contaminant species causes direct electron transfer and subsequent oxidative degradation, followed by adsorption of the breakdown products onto the CNTs. The presence of natural organic matter however has a negative effect on the removal of tetracycline, due to competitive adsorption to CNTs [148]. As discussed in the following section, this purification method has also been applied for the inactivation of viruses in contaminated water [149].…”

Conductive Cotton Filters for Affordable and Efficient Water Purification

“…The TC electrooxidation flux changed negligibly with further increase in the total cell potential until 3.0 V. This finding can be explained by the open-circuit measurements as displayed in Figure 4b. At a total cell potential of 1.5 V, the anode potential was determined to be 0.7 ± 0.06 V (vs. Ag/AgCl), which is high enough to oxide TC molecules (e.g., dimethylamine group of TC at 0.5 V vs. Ag/AgCl) [35]. It is of note that the maximum TC electrooxidation kinetics was 2.0 V, which was quite different with that of MO.…”

“…TC is an amphoteric molecule with multiple functional groups/moieties (e.g., phenol, amino, alcohol, diketone). Moreover, compared with MO, the TC molecules tend to adsorb onto the sp 2 -conjugated CNT sidewalls due to its relatively strong van der Waals, π-π, and cation−π interactions [35]. A recent report has demonstrated that TC has significant 3D molecular curvature and tend to adsorb onto the CNT surface until monolayer formation [35].…”

“…Moreover, compared with MO, the TC molecules tend to adsorb onto the sp 2 -conjugated CNT sidewalls due to its relatively strong van der Waals, π-π, and cation−π interactions [35]. A recent report has demonstrated that TC has significant 3D molecular curvature and tend to adsorb onto the CNT surface until monolayer formation [35]. The LC-MS characterization results suggest that the characteristic TC peak observed in the influent solution was decreased by 63% and 96% at a total cell potential of 1.0 V and 2.0 V, respectively, indicates that the parent TC molecules has been degraded.…”