From hindered to promoted settling in dispersions of attractive colloids: Simulation, modeling, and application to macromolecular characterization
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PhysRevFluids.3.063302.pdf
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Author(s)
Fiore, Andrew Michael
Wang, Gang
Swan, James W
Date Issued
June 2018
Journal
Physical Review Fluids
Publisher
American Physical Society
Citation
Fiore, Andrew M. et al. "From hindered to promoted settling in dispersions of attractive colloids: Simulation, modeling, and application to macromolecular characterization." Physical Review Fluids 3, 6 (June 2018): 063302 © 2018 American Physical Society
Version
Final published version
Abstract
The settling of colloidal particles with short-ranged attractions is investigated via highly resolved immersed boundary simulations. At modest volume fractions, we show that intercolloid attractions lead to clustering that reduces the hinderance to settling imposed by fluid back flow. For sufficient attraction strength, increasing the particle concentration grows the particle clusters, which further increases the mean settling rate in a physical mode termed promoted settling. The immersed boundary simulations are compared to recent experimental measurements of the settling rate in nanoparticle dispersions for which particles are driven to aggregate by short-ranged depletion attractions. The simulations are able to quantitatively reproduce the experimental results. We show that a simple, empirical model for the settling rate of adhesive hard-sphere dispersions can be derived from a combination of the experimental and computational data as well as analytical results valid in certain asymptotic limits of the concentration and attraction strength. This model naturally extends the Richardson-Zaki formalism used to describe hindered settling of hard, repulsive spheres. Experimental measurements of the collective diffusion coefficient in concentrated solutions of globular proteins are used to illustrate inference of effective interaction parameters for sticky, globular macromolecules using this empirical model. Finally, application of the simulation methods and empirical model to other colloidal systems are discussed.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
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DOI of Published Version
https://doi.org/10.1103/PhysRevFluids.3.063302
