Abstract
The transport of manufactured titanium dioxide (TiO2, rutile) nanoparticles (NP) in porous media was investigated under saturated conditions. Experiments were carried out with different fluid velocities, with values in the range of observed velocities in alluvial aquifers. As reported on the literature for different kinds of NPs, the amount of retained NPs decreased when the water velocity increased. Moreover, no retention was observed for ionic strength values smaller than 5mM.A transport model coupling convective–dispersive transport with a Langmuirian kinetic deposition was used to fit the BTCs. Empirical linear equations were developed to estimate the attachment rate ka and the maximal solid phase concentration smax. Both parameters were found to be linearly depending on the collector efficiency (η0). It was also observed that attachment efficiency (α) did not change with increase of water velocity under the given experimental conditions and that the model had a low sensitivity to α. Based on these estimates of the retention parameters, the classical dispersion–convection model coupled with a Langmuir type adsorption model was able to reproduce quite well the observed TiO2 breakthrough curves for every fluid velocity used in the experiments.
Highlights
The nanotechnology industry constantly develops new applications of nanomaterials, exploiting their large spectrum of properties due to their nanometric size (Auffan et al, 2009)
The results show a decrease in the NP mass retained by the porous media when water velocity increases (Table 1), according to classic filtration theory (Zamani and Mainibrownian, 2009, Yao et al, 1971)
A linear behavior as a function of the collector efficiency was observed for retention parameters of the model that describes TiO2 NP mobility in a saturated porous medium under different fluid velocities
Summary
The nanotechnology industry constantly develops new applications of nanomaterials, exploiting their large spectrum of properties due to their nanometric size (Auffan et al, 2009). NPs are present, inter alia, in sunscreens, coatings, paintings, sports clothing, alimentary packaging, solar cells and fuel cells. They are involved in degradation processes for contaminants present in soil and water (Nowack and Bucheli, 2007). A better understanding of the NP life cycle could allow a better evaluation of their movements among ecosystems and the transformations that may occur. In this scenario, the environmental risk assessment of NPs is important to develop adequate regulations for nanoparticle applications (Auffan et al, 2009). TiO2 NPs are among the most used manufactured NPs and, are among the most released in the environment
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