Adsorption of sulfamethoxazole on different types of carbon nanotubes in comparison to other natural adsorbents.

The environmental risks of wide application and occurrence of antibiotics have attracted great concern but their environmental behaviors are still unclear. The fast development of nanotechnology also arise environmental concerns, one of which is that the discharge of nanomaterials into the environment may alter the environmental behavior and risks of various contaminants. This study conducted batch adsorption experiments of sulfamethoxazole (SMX), a widely studied antibiotic, on various carbon nanotubes (CNTs) and sediment particles. The SMX adsorption data on other natural adsorbents were also collected from literature. The surface area of CNTs is an important parameter controlling their adsorption to SMX. Other properties, including diameters and surface functional groups, were also observed to be important in regulating SMX adsorption. Inorganic mineral particles have comparable adsorption coefficients with other natural sorbents including soils, sediments and sludges, suggesting the contribution of inorganic fractions to SMX adsorption could not be ignored and the normalization of adsorption coefficient by organic carbon content should be avoided. The adsorption coefficients of SMX on CNTs were generally two orders of magnitude higher than other natural sorbents. The presence of CNTs in the environment, especially in waste water and solid waste of water treatment plant, could greatly alter SMX behavior as well as its risks.