HR: 1340h
AN: B33C-1434    [Abstracts]
TI: Effect of Natural Organic Matter (NOM) on Properties and Mobility of Aqueous Fullerene Nanoparticles (nC60)
AU: * Xie, B
EM: bin.xie@rice.edu
AF: Rice University Department of Civil and Environmental Engineering, Mail Stop 519 6100 Main Street, Houston, TX 77005, United States
AU: Li, Q
EM: qilin.li@rice.edu
AF: Rice University Department of Civil and Environmental Engineering, Mail Stop 519 6100 Main Street, Houston, TX 77005, United States
AB: C60 fullerene and its derivatives have been used in a number of consumer products and the predicted industrial- scale production of fullerene reaches tons per year. Aqueous fullerene nanoparticles (nC60) could be formed through direct contact of fullerene powder with water or through organic solvent exchange. Existing toxicity data of nC60 indicate that industrial-scale production of fullerene poses a potential threat to the environment. There is a need to evaluate the fate and transport of nC60 in the aqueous environment and its subsequent impact on the bio- and eco- systems. Our study aims to determine the effect of natural organic matter (NOM) on the nC60 entry pathway, physicochemical properties, deposition and mobility in the aqueous phase. Experimental conditions cover those typical of natural waters. Stable nC60 suspensions formed under four different conditions in the presence and absence of two major NOM components, humic acid (HA) and fulvic acid (FA), were thoroughly characterized for particle size, morphology, electrophoretic mobility, and UV absorbance. nC60 deposition experiments were carried out in parallel cross-flow chambers monitored by quartz crystal microbalance (QCM) and the nC60 mass deposition kinetics was studied in the absence and presence of NOM. Our study found that the size, structure and surface properties of readily formed nC60 changed fundamentally upon addition of NOM at environmental concentrations. For example, nC60 prepared through dissolution and removal of toluene solvent by sonication decreased in particle size, and the degree of particle size reduction was a function of solution chemistries. Bulk phase fullerene powder was directly dispersed into the aqueous phase as stable nC60 colloidal suspensions in presence of NOM at environmental concentrations in less than three days. In both cases, extremely small nC60 nanoparticles with diameter less than 10 nm were prevalently formed at specific solution conditions. The nC60 mass deposition followed zero-order kinetics onto silicon dioxide surface, at an nC60 concentration of 3 mg/L regardless of the NOM concentration (0 – 20 mg/L). The nC60 mass deposition rate decreased gradually in presence of increasing amount of NOM. For example in a solution condition of 10 mM CaCl2, nC60 was deposited onto silicon dioxide surface at a rate of 24 nghr-1 without any NOM, yet the rate was decreased to 20 nghr-1 in presence of 10 mg/L HA, and was further decreased to only 10 nghr-1 in presence of 20 mg/L HA. Our study indicates that NOM significantly increases the stability and mobility of nC60 nanoparticles in the aqueous environment.
DE: 0432 Contaminant and organic biogeochemistry (0792)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting