Speaker
Description
Crystallization Of Sodium Chloride In Microfluidic Pore Systems
Keywords: Microfluidics, Porous Media, Salt Crystallization, SEM
Salt crystallization in porous media induced by drying involves complex coupling between drying kinetics, wettability phenomena, pore size and salt structure 1. In this context, this work aims at observing sodium chloride subflorescence growth during evaporation in porous media, focusing on the shape and properties of the resulting salt structures (porosity, permeability) depending on pore size and wettability. To this end, we develop two-dimensional microfluidic chips mimicking simple porous geometries 2, allowing optical microscopy observation of crystallization kinetics. The study explores the impact of geometrical confinement and wettability on salt crystallization. Different hydrophilic/hydrophobic patterns are created to stabilize the evaporative front in the model porous media and force subflorescence formation. Our microfluidic devices, designed to be reopened after drying, allow further analysis of the remaining crystals through Scanning Electron Microscopy (SEM).
Two types of salt structure are observed: monocrystals forming in solution and porous aggregates developing in dry areas from the liquid front. The evaporation rate plays a significant role, influencing concentration dynamics in the channel and the typical size of aggregates in the dry region. Moreover, the hydrophilic nature of the crystals drives solution towards the aggregates, advancing the wet front into the hydrophobic regions. In particular, the study highlights a mechanism of dissolution of the monocrystals taking place as the salt aggregates develop in the hydrophobic region.
Acknowledgements: Financial support from project “Drysalt” funded by GIP ANR (Project: ANR-22-CE51-0041-02) is gratefully acknowledged.
References:
1 - Salt crystallization in Porous Media, co-edited by H. Derluyn and M. Prat, 2024, ISTE-Wiley
2 - Kim, M., Sell, A., Sinton, D., 2013, Aquifer-on-a-chip : understanding pore-scale salt precipitation dynamics during CO2 sequestration, Lab on a chip, 13, 2508-2518
| References | Salt crystallization in Porous Media, co-edited by H. Derluyn and M. Prat, 2024, ISTE-Wiley; Kim, M., Sell, A., Sinton, D., 2013, Aquifer-on-a-chip : understanding pore-scale salt precipitation dynamics during CO2 sequestration, Lab on a chip, 13, 2508-2518 |
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| Country | France |
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