Enhanced Transport of 2,2′,5,5′-Polychlorinated Biphenyl by Natural Organic Matter (NOM) and Surfactant-Modified Fullerene Nanoparticles (nC60)

Abstract

Stable colloidal suspensions of buckminsterfullerene (nC(60)) in aqueous environments can significantly affect the fate and transport of hydrophobic organic contaminants by serving as a contaminant carrier. In this study, we examined enhanced transport of 2,2',5,5'-polychlorinated biphenyl (PCB) in saturated sandy soil columns by a variety of nC(60) samples, including an nC(60) sample prepared by the typical solvent exchange method, as well as eight natural organic matter (NOM) or surfactant-modified nC(60) samples, prepared by phase-transferring C(60) from toluene to an NOM or a surfactant solution. Whereas the NOM- and surfactant-modified nC(60) samples have mobility similar to the unmodified nC(60), their contaminant-mobilizing capabilities are significantly greater: breakthrough of PCB increases by 47.2 to 227% with the surfactant-modified nC(60) samples and by 233 to 370% with the NOM-modified nC(60) samples. The significantly enhanced contaminant-mobilizing capability of the modified nC(60) is likely due to a combined effect of increased adsorption affinities and increased tendency of desorption nonequilibrium, likely caused by the changes of nC(60) aggregation properties induced by the presence of NOM or surfactant. Findings in this study indicate that nC(60) formed in different processes might have vastly different effects on contaminant fate and transport.