Sorption of triclosan by carbon nanotubes in dispersion: The importance of dispersing properties using different surfactants

Abstract

The production of carbon nanotubes (CNTs) increased rapidly due to the superior properties and was suggested to be the potential sorbents for environmental remediation. CNTs tend to form aggregates, thus CNTs dispersion was commonly produced by sonication with surfactant in industry for better application. In the present study, a novel passive sampling method was used to systematically study sorption of triclosan to CNTs dispersion to give a better understanding on their interactions especially with the presence of surface-active substances. With the increase of anionic surfactant concentration (SDBS or SDS), sorption of triclosan was gradually suppressed. CNTs dispersed by nonionic surfactant TX-100 increased or decreased sorption at different TX-100 and triclosan concentration. Little amount of cationic surfactant CTAB(1 mg/L) could sharply decrease triclosan sorption to CNTs but with larger CTAB concentration, sorption was continually increased. Sorption isotherms of triclosan to CNTs dispersion with 40 mg/L and 100 mg/L surfactant fitted well with Toth model show the existence of double competition in the sorption process. Different from the adsorption mechanism of previously aggregated CNTs and compounds. Sorption data combined with comprehensive characterization of CNTs dispersion and theoretical analysis, three effects referring to charge, dispersion and competition were proposed. Sorption coefficient was linearly correlated with the characterization parameters. Surface charge, dispersion status and surfactant concentration play the important role on triclosan sorption in CNTs dispersion in the presence of anionic, cationic and nonionic surfactant, respectively. The results provide basic supports on application of CNTs in remediation area and exploring the fate of both CNTs dispersion and pollutants.