Nanoparticle transport in water-unsaturated porous media: effects of solution ionic strength and flow rate

Abstract : This paper presents the influence of ionic strength and flow on nanoparticle (NP) retention rate in an unsaturated calcareous medium, originating from a heterogeneous glaciofluvial deposit of the region of Lyon (France). Laboratory columns 10 cm in diameter and 30 cm in length were used. Silica nanoparticles (Au-SiO2-FluoNPs), with hydrodynamic diameter rang- ing from 50 to 60 nm and labeled with fluorescein derivatives, were used to simulate particle transport, and bromide was used to characterize flow. Three flow rates and five different ionic strengths were tested. The transfer model based on fractionation of water into mobile and immobile fractions was coupled with the attachment/detachment model to fit NPs breakthrough curves. The results show that increasing flow velocity induces a decrease in nanoparticle retention, probably as the result of several physical but also geochemical fac- tors. The results show that NPs retention increases with ionic strength. However, an inversion of retention occurs for ionic strength >5.10−2 M, which has been scarcely observed in previous studies. The measure of zeta potential and DLVO calculations show that NPs may sorb on both solid-water and air-water interfaces. NPs size distribution shows the potential for nanoparti- cle agglomeration mostly at low pH, leading to entrap- ment in the soil pores. These mechanisms are highly sensitive to both hydrodynamic and geochemical con- ditions, which explains their high sensitivity to flow rates and ionic strength.
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Submitted on : Monday, March 5, 2018 - 3:25:38 PM
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Dieuseul Prédelus, Laurent Lassabatere, Cédric Louis, Hélène Gehan, Thomas Brichart, et al.. Nanoparticle transport in water-unsaturated porous media: effects of solution ionic strength and flow rate. Journal of Nanoparticle Research, Springer Verlag, 2017, 19 (3), ⟨10.1007/s11051-017-3755-4⟩. ⟨hal-01723497⟩

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