Speaker
Description
The 3D characterization of a porous medium is fundamental for understanding the pore-scale mechanisms that control matrix-fluid interactions in flow-through systems. For instance, nanoparticle mobility in porous media is a key challenge within the nanoremediation technology, as the reactive nanoparticles are to target specific areas of the contaminated aquifer. Over the past two and a half decades, laboratory and field research have shown that metal nanoparticles can rapidly degrade some contaminants in-situ, resulting in non-toxic products.
Nonetheless, the 3D microscopic details of the nanoremediation process at a pore scale have only been investigated recently using X-ray computed microtomography (XR-mCT). Previous studies of zero-valent iron nanoparticles (nZVI) injection in porous media using synchrotron-based XR-mCT have performed a single round of nanoparticle injection (Pak et al., 2020; Schiefler et al., 2022; Fopa et al., 2023) and have shown TCE degradation by nZVI (Pak et al., 2020).
We have used XR-mCT at a synchrotron facility to further investigate the pore-scale dynamics of nZVI mobility/retention in the porous media where multiple rounds of nanoparticle injections are performed. We aimed to obtain a closer representation of the fieldwork process, where the nZVI injection is typically performed in multiple stages. Additionally, our experiment ran with small variations in flow rate, and with a suspension with higher nanoparticle concentration (50 g/L) compared with previous studies.
At the used concentration, small variations in flow rate (less than an order of magnitude) are not significant for increasing nanoparticle mobility, as discussed in previous studies. The history of nanoparticle flow, experienced when performing multiple injections within the field, is actually a more influential factor regarding particle retention. Results indicate that mechanisms acting during nZVI injection are mainly governed by matrix-particle (filtering and straining) and particle-particle (ripening) interactions. Moreover, the ripening mechanism is understood to play a key role in the entrapment of nZVI within the samples evaluated, indicating that nanoparticle history is significant in the mobility and entrapment of nanoparticles in porous media. This data provides valuable insights for evaluating contaminated sites and designing effective remediation plans.
| References | Fopa, R. D.; Bianco, C.; Archilha, N. L.; Moreira, A. C.; Pak, T. (2023). A pore-scale investigation of the effect of nanoparticle injection on properties of sandy porous media. Journal of Contaminant Hydrology, 253: 104126. 10.1016/j.jconhyd.2022.104126 Pak, T., Luz, L. F. de L., Tosco, T., Costa, G. S. R., Rosa, P. R. R., & Archilha, N. L. (2020). Pore-scale investigation of the use of reactive nanoparticles for in situ remediation of contaminated groundwater source. Proceedings of the National Academy of Sciences, 117(24), 201918683. https://doi.org/10.1073/pnas.1918683117 Schiefler, A. A.; Bruns, S.; Müter, D. Uesugi, K.; Sørensencf, H. O.; Toblerag, D. J. (2022). Retention of sulfidated nZVI (S-nZVI) in porous media visualized by X-ray μ-CT – the relevance of pore space geometry. Environmental Science Nano, 9: 3439. 10.1039/d2en00224h |
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| Country | Brazil |
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