Investigation of the Transport and Deposition of Fullerene (C60) Nanoparticles in Quartz Sands under Varying Flow Conditions

Abstract

A coupled experimental and mathematical modeling investigation was undertaken to explore nanoscale fullerene aggregate (nC60) transport and deposition in water-saturated porous media. Column experiments were conducted with four different size fractions of Ottawa sand at two pore-water velocities. A mathematical model that incorporates nonequilibrium attachment kinetics and a maximum retention capacity was used to simulate experimental nC60 effluent breakthrough curves and deposition profiles. Fitted maximum retention capacities (S(max)), which ranged from 0.44 to 13.99 microg/g, are found to be correlated to normalized mass flux. The developed correlation provides a means to estimate S(max) as a function of flow velocity, nanoparticle size, and mean grain size of the porous medium. Collision efficiency factors, estimated from fitted attachment rate coefficients, are relatively constant (approximately 0.14) over the range of conditions considered. These fitted values, however, are more than 1 order of magnitude larger than the theoretical collision efficiency factor computed from Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (0.009). Data analyses suggest that neither physical straining nor attraction to the secondary minimum is responsible for this discrepancy. Patch-wise surface charge heterogeneity on the sand grains is shown to be the likely contributor to the observed deviations from classical DLVO theory. These findings indicate that modifications to clean-bed filtration theory and consideration of surface heterogeneity are necessary to accurately predict nC60 transport behavior in saturated porous media.

Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media

“…• Clean bed with site blocking model, where a maximum retention capacity S max was added to constrain the NPs deposition [19], given by the equations below:…”

“…The nanoparticle deposition in porous media is conceptualized as a two-step process consisting of particle transport to the vicinity of glass beads surface, followed by attachment [19].The transport process is controlled by the models described in Section 2.5.1, while the particle attachment process is governed by the interaction forces between particle and grain surface, which is controlled by the DLVO theory.…”

“…Retention and transport of CNPs in porous media has received considerable attention recently. For example, the retention and transport of dispersed aggregations of fullerene [15][16][17][18][19][20][21], graphene oxide particle; (2) the effect of concentration and particle size on NPs' retention and transport in saturated porous media. ; and (3) the applicability of the DLVO theory to describe the deposition of CNPs on sand surfaces.…”

Contaminant‐mobilizing capability of fullerene nanoparticles (nC60): Effect of solvent‐exchange process in nC60 formation

“…Interestingly, C 60 can be made available in water as stable, nanoscale, colloidal suspensions (referred to as nC 60 herein) through various methods, such as solvent exchange, sonication, or long-term stirring without a solvent [8][9][10][11][12]. Nanoscale C 60 can be stable in aqueous environments for prolonged periods (months to years) and has a high potential for migration through soil and aquifer materials under common environmental conditions [13][14][15].…”

In vivo toxicity of nano-C60 aggregates complex with atrazine to aquatic organisms

“…However, water stable nano-aggregates of C 60 (termed nC 60 ) can be formed from pristine C 60 in certain conditions, for example, by solvent exchanging (such as tetrahydrofuran and toluene) [8], hand-grinding [9], and prelonged stirring in water [10]. As it may be a most environmentally relevant form of C 60 [11], nC 60 has recently caused much concern about its toxicity to humans and the environment, though its concentration is usually less than 10 mg/L in aquatic environment [12,13]. Although the composition and surface chemistry of nC 60 are not well understood, studies have shown that nC 60 are toxic to different biological systems, such as cells [14][15][16], bacteria [11,17,18], daphnia [19,20], and fishes [20][21][22].…”