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Unidirectional drying of a suspension of diffusiophoretic colloids under gravity
Jinjie Xu1, Zhikui Wang1, Henry C W Chu1
1Department of Chemical Engineering, University of Florida Gainesville FL 32611 USA h.chu@ufl.edu.
RSC Advances
|March 23, 2023
Summary
Gravity significantly impacts colloidal suspension drying. Diffusiophoresis, colloid transport via electrolyte gradients, was explored, revealing it can create thinner or thicker layers depending on colloid-solute interactions, crucial for space and ground applications.
Area of Science:
- Colloid and Interface Science
- Fluid Dynamics
- Transport Phenomena
Background:
- Gravity influences unidirectional drying of colloidal suspensions.
- The role of diffusiophoresis in gravity-driven drying remains unexplored.
- Diffusiophoresis is colloid transport driven by electrolyte concentration gradients.
Purpose of the Study:
- To analyze electrolyte-colloid suspension transport during unidirectional drying under gravity and diffusiophoresis.
- To develop a macrotransport theory for this system.
- To understand how diffusiophoresis affects colloidal layer formation and separation.
Main Methods:
- Direct numerical simulations of drying colloidal suspensions.
- Development of a macrotransport theory.
- Analysis of advective-diffusive transport influenced by gravity and diffusiophoresis.
Main Results:
- Solute-attracted diffusiophoretic colloids yield the thinnest layers and strongest phase separation.
- Strongly solute-repelled colloids show negligible gravity effects due to diffusiophoresis preventing concentration gradients.
- New theoretical scalings predict colloidal layers an order of magnitude thicker for solute-repelled colloids compared to others.
Conclusions:
- Diffusiophoresis plays a critical role in modulating gravity's effect on colloidal layer formation during drying.
- Tailoring colloid-electrolyte interactions can control separation efficiency.
- Findings are relevant for Earth-based and microgravity applications.
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