Mobility and settling rate of agglomerates of polydisperse nanoparticles

Anastasia Spyrogianni, Katerina S. Karadima, Eirini Goudeli, Vlasis G. Mavrantzas, Sotiris E. Pratsinis

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Agglomerate settling impacts nanotoxicology and nanomedicine as well as the stability of engineered nanofluids. Here, the mobility of nanostructured fractal-like SiO2 agglomerates in water is investigated and their settling rate in infinitely dilute suspensions is calculated by a Brownian dynamics algorithm tracking the agglomerate translational and rotational motion. The corresponding friction matrices are obtained using the HYDRO++ algorithm [J. G. de la Torre, G. del Rio Echenique, and A. Ortega, J. Phys. Chem. B 111, 955 (2007)] from the Kirkwood-Riseman theory accounting for hydrodynamic interactions of primary particles (PPs) through the Rotne-Prager-Yamakawa tensor, properly modified for polydisperse PPs. Agglomerates are generated by an event-driven method and have constant mass fractal dimension but varying PP size distribution, mass, and relative shape anisotropy. The calculated diffusion coefficient from HYDRO++ is used to obtain the agglomerate mobility diameter dm and is compared with that from scaling laws for fractal-like agglomerates. The ratio dm/dg of the mobility diameter to the gyration diameter of the agglomerate decreases with increasing relative shape anisotropy. For constant dm and mean dp, the agglomerate settling rate, us, increases with increasing PP geometric standard deviation σp,g (polydispersity). A linear relationship between us and agglomerate mass to dm ratio, m/dm, is revealed and attributed to the fast Brownian rotation of such small and light nanoparticle agglomerates. An analytical expression for the us of agglomerates consisting of polydisperse PPs is then derived, us=1-ρfρpg3πμmdm (ρf is the density of the fluid, ρp is the density of PPs, μ is the viscosity of the fluid, and g is the acceleration of gravity), valid for agglomerates for which the characteristic rotational time is considerably shorter than their settling time. Our calculations demonstrate that the commonly made assumption of monodisperse PPs underestimates us by a fraction depending on σp,g and agglomerate mass mobility exponent. Simulations are in excellent agreement with deposition rate measurements of fumed SiO2 agglomerates in water.

Original languageEnglish (US)
Article number064703
JournalJournal of Chemical Physics
Volume148
Issue number6
DOIs
StatePublished - Feb 14 2018

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settling
Fractals
Anisotropy
Nanoparticles
Medical nanotechnology
nanoparticles
Fluids
Water
Scaling laws
Polydispersity
Fractal dimension
Deposition rates
Particle size analysis
Tensors
fractals
Suspensions
Gravitation
Hydrodynamics
Viscosity
Friction

Cite this

Spyrogianni, A., Karadima, K. S., Goudeli, E., Mavrantzas, V. G., & Pratsinis, S. E. (2018). Mobility and settling rate of agglomerates of polydisperse nanoparticles. Journal of Chemical Physics, 148(6), [064703]. https://doi.org/10.1063/1.5012037

Mobility and settling rate of agglomerates of polydisperse nanoparticles. / Spyrogianni, Anastasia; Karadima, Katerina S.; Goudeli, Eirini; Mavrantzas, Vlasis G.; Pratsinis, Sotiris E.

In: Journal of Chemical Physics, Vol. 148, No. 6, 064703, 14.02.2018.

Research output: Contribution to journalArticle

Spyrogianni, A, Karadima, KS, Goudeli, E, Mavrantzas, VG & Pratsinis, SE 2018, 'Mobility and settling rate of agglomerates of polydisperse nanoparticles', Journal of Chemical Physics, vol. 148, no. 6, 064703. https://doi.org/10.1063/1.5012037
Spyrogianni A, Karadima KS, Goudeli E, Mavrantzas VG, Pratsinis SE. Mobility and settling rate of agglomerates of polydisperse nanoparticles. Journal of Chemical Physics. 2018 Feb 14;148(6). 064703. https://doi.org/10.1063/1.5012037
Spyrogianni, Anastasia ; Karadima, Katerina S. ; Goudeli, Eirini ; Mavrantzas, Vlasis G. ; Pratsinis, Sotiris E. / Mobility and settling rate of agglomerates of polydisperse nanoparticles. In: Journal of Chemical Physics. 2018 ; Vol. 148, No. 6.
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