The main purpose of this study was to characterize the adsorption and desorption interactions of naphthalene, a model environmental organic pollutant, with C60 fullerene. C60 fullerene was used as a model adsorbent for carbonaceous nanoparticles. Typical batch reactors were used to perform adsorption and desorption experiments. Adsorption and desorption of naphthalene to and from C60 fullerene solids in different aggregation forms was studied, where C60 was used as purchased, deposited as a thin film, or dispersed in water by magnetic mixing. Adsorption and desorption of naphthalene to activated carbon, a common sorbent, was also studied and compared with that of C60. It was found in this study that the enhanced dispersal of C60 could affect the adsorption of naphthalene by several orders of magnitude. A solid-water distribution coefficient of 102.4 mL·g-1 was obtained for adsorption of naphthalene to poorly dispersed C60, whereas (104.2 to 104.3) ml·g-1 coefficients were obtained for well-dispersed C60 samples. In addition, desorption of naphthalene from dispersed C60 samples into aqueous solutions was found to exhibit strong hysteresis. For the desorption over a period of 60 days, only about 11% of total naphthalene was desorbed from C60. Possible mechanisms for these observations are discussed.

In this study, the transport of water-stable “nano-C60 particles” (a term used to refer to underivatized C60 crystalline nanoparticles, stable in water for months) through a soil column (packed with Lula soil, 0.27% organic carbon) was investigated for the first time. Nano-C60 particle breakthrough experiments were conducted at different flow rates, while other column operating parameters remained fixed through all the experiments. Nano-C60 particles were observed to be more mobile at higher flow velocity: at the flow velocity of 0.38 m/d, the maximum percent of nano-C60 breakthrough (C/C0) was 47%; at the flow velocity of 3.8 m/d, the plateau value of nano-C60 breakthrough was 60%; and at the flow velocity of 11.4 m/d, the plateau value of nano-C60 breakthrough was almost 80%. At the low flow velocity (0.38 m/d), which is typical of groundwater flow, nano-C60 particles showed very limited mobility: after about 57 pore volumes, they deposited to the soil column so rapidly that virtually no nano-C60 was detected in the effluent. This observed “favorable deposition” (attachment efficiency α = 1) was probably due to “filter ripening.” Also the release of nano-C60 particles after flow interruption was observed. The transport of naphthalene through the same soil column containing 0.18% nano-C60 particles deposited was measured. A retardation factor of about 13 was observed, possibly suggesting that sorbed nano-C60 particles in the soil column sorbed naphthalene similar to soil organic carbon. An asymmetric naphthalene breakthrough curve was observed, which is possibly due to “sorption nonequilibrium.”

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