Dispersion of fullerenes in natural water and their behavior in water treatment process

Abstract

Environmental impact of fullerenes such as C60 and carbon nanotubes is of great concern due to the projection for widespread application and mass production in near future. Understanding their fate in the aqueous phase is prerequisite for accurate assessment of their ecotoxicological and human health effects upon unintended release to environment. This research addresses outstanding questions related to the behavior of fullerenes in natural and engineered water environments. Specifically, this research focuses on investigating: 1) the stability of fullerenes in the natural water, 2) interaction between fullerenes and natural organic matter (NOM), and 3) treatability of water stable fullerenes by conventional water treatment process. The experimental results suggested that NOM readily interacts with fullerenes leading to the formation of water stable fullerene suspensions. The adsorptive interaction between NOM and fullerenes was largely affected by NOM characteristics as well as water quality parameters. The fate of fullerenes in water environments was also greatly influenced by the types of fullerenes (e.g., single walled carbon nanotubes, multi-walled carbon nanotubes, and C60) and the pathway they are introduced into the aqueous phase. These water stable fullerene suspensions were found to be relatively well removed by conventional water treatment processes while the presence of NOM could negatively impact the removal efficiency. The outcomes of this study collectively imply that the dispersion of fullerenes in the natural water can occur beyond the level predicted only based on their extreme hydrophobicity and NOM plays a critical role on the fate of fullerenes both in natural and engineered water environments.