Browsing by Author "Cheng, Xuekun"

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    Carbon-60 nanoparticles: Adsorption and desorption of organic contaminants, and transport in soil
    (2006) Cheng, Xuekun; Tomson, Mason B.
    C 60 is a new form of carbon with unique properties due to its small size. Since it has been predicted that C 60 will be manufactured by tons, there is no doubt that it will ultimately find their way to the environment. Because of the insolubility of C 60 in water, one might expect that it would not enter groundwater in great quantities. However, "nC 60 " (water-stable C 60 aggregates) can be formed in water by exchange of solvents, or simply by stirring, indicating that C 60 might be readily available in groundwater. Therefore it is necessary to investigate the transport of C 60 particles and their interactions with other environmental contaminants. The adsorption and desorption of naphthalene and 1,2-dichlorobenzene, two common organic contaminants, with nC 60 in water was investigated and sorption hysteresis was observed. Naphthalene adsorption-desorption with activated carbon particles and soil organic carbon was also conducted. Similar sorption hysteresis was observed. Experimental data were fitted with different sorption models. The Dual-Equilibrium desorption model fits experimental data well. Each DED model fitting parameter has similar values for all three forms of carbon, indicating the possibility to predict the carbonaceous nanomaterial-contaminant interactions from well known carbon materials. The transport of nC 60 through a soil column was characterized by flow-through apparatus. It was observed in the transport study that nC 60 have limited mobility in the soil column at typical groundwater velocity, but they were more mobile at higher velocities. The effect of adsorbed nC 60 on naphthalene is similar to that of soil organic carbon. This study provides useful information for the environmental risk assessment of C 60 fullerene.
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    Environmental impact of carbonaceous nanomaterials: Adsorption and desorption of naphthalene from aqueous buckminsterfullerene fullerene
    (2003) Cheng, Xuekun; Tomson, Mason B.
    Adsorption and desorption of naphthalene from C60 fullerene solids in different aggregation forms was studied in this work, where C 60 was used as purchased; or dispersed in water by magnetic mixing; or deposited as a thin film. Finally C60 colloidal dispersion was produced in water with the help of high-energy sonication probe. Sorptive properties of C60 colloidal particles were also studied with naphthalene. Sorption partition coefficients could vary by orders of magnitude and have been observed to be related to the different C60 aggregation forms. Sorption/desorption hysteresis, a common phenomenon observed in natural soils and sediments, was also observed in this work with naphthalene sorbed to well dispersed C60 aggregates. Data were fitted with dual-equilibrium desorption model and results were comparable to literature reported results for natural organic carbons.