Issue 14, 2023

Unidirectional drying of a suspension of diffusiophoretic colloids under gravity

Abstract

Recent experiments (K. Inoue and S. Inasawa, RSC Adv., 2020, 10, 15763–15768) and simulations (J.-B. Salmon and F. Doumenc, Phys. Rev. Fluids, 2020, 5, 024201) demonstrated the significant impact of gravity on unidirectional drying of a colloidal suspension. However, under gravity, the role of colloid transport induced by an electrolyte concentration gradient, a mechanism known as diffusiophoresis, is unexplored to date. In this work, we employ direct numerical simulations and develop a macrotransport theory to analyze the advective–diffusive transport of an electrolyte-colloid suspension in a unidirectional drying cell under the influence of gravity and diffusiophoresis. We report three key findings. First, drying a suspension of solute-attracted diffusiophoretic colloids causes the strongest phase separation and generates the thinnest colloidal layer compared to non-diffusiophoretic or solute-repelled colloids. Second, when colloids are strongly solute-repelled, diffusiophoresis prevents the formation of colloid concentration gradient and hence gravity has a negligible effect on colloidal layer formation. Third, our macrotransport theory predicts new scalings for the growth of the colloidal layer. The scalings match with direct numerical simulations and indicate that the colloidal layer produced by solute-repelled diffusiophoretic colloids could be an order of magnitude thicker compared to non-diffusiophoretic or solute-attracted colloids. Our results enable tailoring the separation of colloid-electrolyte suspensions by tuning the interactions between the solvent, electrolyte, and colloids under Earth's or microgravity, which is central to ground-based and in-space applications.

Graphical abstract: Unidirectional drying of a suspension of diffusiophoretic colloids under gravity

Article information

Article type
Paper
Submitted
06 yan 2023
Accepted
13 mar 2023
First published
20 mar 2023
This article is Open Access
Creative Commons BY license

RSC Adv., 2023,13, 9247-9259

Unidirectional drying of a suspension of diffusiophoretic colloids under gravity

J. Xu, Z. Wang and H. C. W. Chu, RSC Adv., 2023, 13, 9247 DOI: 10.1039/D3RA00115F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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