Aging of Carbon Nanotubes Increases Their Adsorption towards Tetracycline

Due to wide range of their applications, a large amount of carbon nanotubes (CNTs) is discharged into natural water. As an inevitable environmental fate, aging changes the physicochemical properties of carbon nanotubes, which in turn affects their interactions with other pollutants. In this study, the aging of CNTs accelerated with non-thermal plasma, and the interaction between aged CNTs and tetracycline were explored. The physicochemical properties of CNTs after aging were evaluated with specific surface area, zeta potential, FTIR, Raman, and XPS analysis. Adsorption and site energy distribution analyses were applied to explore the interaction between aged carbon nanotubes and tetracycline antibiotics. After aging, the specific surface area of carbon nanotubes decreases, defects increase, and the crystal morphology is disordered. More oxygen-containing functional groups are generated on the CNTs surface, including carbonyl, carboxyl, and hydroxyl groups. In addition, aged CNTs exhibited higher adsorption capacity for tetracycline. The results indicate that carbon nanotubes can adsorb more tetracycline after aging, which means that more antibiotics such as tetracycline may be enriched and transported on carbon nanotubes.