Contaminant‐mobilizing capability of fullerene nanoparticles ( n C 60 ): Effect of solvent‐exchange process in n C 60 formation

Fullerene nanoparticles ( n C 60 ) in aqueous environments can significantly enhance the transport of hydrophobic organic contaminants by serving as a contaminant carrier. In the present study, the authors examine the effect of the solvent‐exchange process on n C 60 aggregate formation and, subsequently, on n C 60 's contaminant‐mobilizing capability. A series of n C 60 samples were prepared using a modified toluene – water solvent‐exchange method through the inclusion of a secondary organic solvent in the phase transfer of molecular C 60 in toluene to n C 60 in water. Two groups of solvents—a water‐miscible group and a non–water‐miscible group—of varied polarity were selected as secondary solvents. The involvement of a secondary solvent in the phase transfer process had only small effects on the particle size and distribution, ζ potential, and mobility of the n C 60 products but significantly influenced the capability of n C 60 to enhance the transport of 2,2′,5,5′‐polychlorinated biphenyl (PCB) in a saturated sandy soil column, regardless of whether the secondary solvent was water‐miscible or non–water‐miscible. The two groups of secondary solvents appear to affect the aggregation properties of n C 60 in water via different mechanisms. In general, n C 60 products made with a secondary water‐miscible solvent have stronger capabilities to enhance PCB transport. Taken together, the results indicate that according to formation conditions and solvent constituents, n C 60 will vary significantly in its interactions with organic contaminants, specifically as related to adsorption or desorption as well as transport in porous media. Environ. Toxicol. Chem. 2013;32:329–336. © 2012 SETAC