Transport of Fullerene Nanoparticles (nC₆₀) in Saturated Sand and Sandy Soil: Controlling Factors and Modeling

Abstract

Understanding subsurface transport of fullerene nanoparticles (nC(60)) is of critical importance for the benign use and risk management of C(60). We examined the effects of several important environmental factors on nC(60) transport in saturated porous media. Decreasing flow velocity from approximately 10 to 1 m/d had little effect on nC(60) transport in Ottawa sand (mainly pure quartz), but significantly inhibited the transport in Lula soil (a sandy, low-organic-matter soil). The difference was attributable to the smaller grain size, more irregular and rougher shape, and greater heterogeneity of Lula soil. Increasing ionic strength and switching background solution from NaCl to CaCl(2) enhanced the deposition of nC(60) in both sand and soil columns, but the effects were more significant for soil. This was likely because the clay minerals (and possibly soil organic matter) in soil responded to changes of ionic strength and species differently than quartz. Anions in the mobile phase had little effect on nC(60) transport, and fulvic acid in the mobile phase (5.0 mg/L) had a small effect in the presence of 0.5 mM Ca(2+). A two-site transport model that takes into account both the blocking-affected attachment process and straining effects can effectively model the breakthrough of nC(60).

Transport of carboxyl-functionalized carbon black nanoparticles in saturated porous media: Column experiments and model analyses

“…1-1a, 1-1b, 1-4a, and 1-4b) also indicated that more CBNPs can attach to the surface of quartz sand at lower flow rates than at higher flow rates. Similar findings have been reported for carbon nanomaterials (fullerene, SWCNT, MWCNT) by several researchers (Jaisi and Elimelech, 2009;Lecoanet and Wiesner, 2004;Li et al, 2008;Liu et al, 2009;Mekonen et al, 2013;Zhang et al, 2012a), demonstrating that mobility of carbon nanomaterials in porous media was enhanced as flow rate increased. Extent of CBNP attachment is expected to decrease with an increment in flow rate (pore water velocity, v), because the interaction time between CBNPS and quartz sand decreases as v increases.…”

“…From the Maxwell model, α theory in CaCl 2 0.1 mM was 7.93 × 10 − 5 , which was 3.5 times larger than that (2.29 × 10 − 5 ) in NaCl 0.1 mM (Table 3), demonstrating that the attachment of CBNPs to quartz sand in CaCl 2 0.1 mM could be greater than that in NaCl 0.1 mM. Similar findings have been reported by Zhang et al (2012a) who performed column experiments to determine the effect of NaCl and CaCl 2 on the transport behavior of fullerene nanoparticles in Ottawa sand and Lula soil. These authors demonstrated the greater impact of Ca 2+ (enhancement of fullerene deposition on porous media) than Na + on the transport of the fullerene.…”

Carbon nanomaterials in clean and contaminated soils: environmental implications and applications

“…The influence of cations on the behaviour of CNMs is well illustrated by the extent to which physical straining (filtering out) of nC 60 occurs in saturated porous media. Zhang et al (2012a) found that columns of pure quartz resulted in very limited nanoparticle deposition even at low flow velocities, whereas a heterogeneous sandy soil with low OM content and small, irregular and rough grains of sand, significantly inhibited nC 60 transport. With the addition of CaCl 2 , greater deposition of nC 60 www.soil-journal.net/1/1/2015/ SOIL, 1, 1-21, 2015…”

“…For both the sand and soil columns, Ca 2+ had a much larger effect on the transport of nC 60 than Na + at the same ionic strengths . This most likely occurred due to efficient neutralisation of surface charges on both nC 60 and sand and soil particles by Ca 2+ relative to Na + , which reduced the electrostatic repulsion (Kuznar and Elimelech, 2004;Zhang et al, 2012a). When considering the fate and behaviour of CNMs in soils, solid peat may have a different impact to that of molecular DOM under environmentally relevant ionic conditions.…”

Interaction between Cu2+ and different types of surface-modified nanoscale zero-valent iron during their transport in porous media

“…Straining refers to both wedging (retention of particles at two bounding surfaces) and bridging (when multiple particles collide and are retained in a pore constriction) (Bradford and Torkzaban, 2008;Zhang et al, 2012). Straining occurs when a nanoparticle is physically removed from flow by the size of the channel, which is prevalent in cases with larger nanoparticles or smaller porous media size.…”