Carbon nanotube environmental fate and interaction with organic pollutants

Knowledge of CNT fate in aqueous environments provides important information regarding their possible environmental impacts. The dispersion stability of carbon nanotubes (CNTs) in aqueous media and their interaction with dissolved polycyclic aromatic hydrocarbons (PAHs) was investigated. Five different CNTs, including one single walled carbon nanotube (SWCNT), two multi walled carbon nanotubes (MWCNT-2 and MWCNT-3) and two functionalised MWCNTs (MWCNT-OH and MWCNT-COOH) were dispersed in two types of media; moderately hard reconstituted water (MHRW) and OECD algae growth media (TG 201). Stock solutions (100 mg/L) were prepared by adding CNTs to appropriate media containing Suwannee River natural organic matter (SR-NOM; 20 mg/L) and sonicated. The dispersion stability and settling of the CNTs in the two media was determined both in the absence and presence of SR-NOM (20 mg/L) by measuring the concentration of CNTs in the water phase over a period of 14 days (UV-vis, 800 nm). The results indicate that the fate of the CNTs in the environment might vary substantially both with CNT properties and the concentration of NOM. The adsorption of phenanthrene to the five types of CNTs was also investigated. The CNTs were dispersed in synthetic freshwater (MHRW) containing SR-NOM as described above. Specific surface area and surface chemistry of the CNTs appear to influence their adsorption of organic pollutants such as phenanthrene.