(482j) Diffusiophoresis of a Spherical Particle in Porous Media: Effects of Electrolyte Valence Asymmetry

Diffusiophoresis refers to the deterministic motion of particles induced by a surrounding concentration gradient of solutes. Recently, we have developed a mathematical model that can predict the diffusiophoretic mobility of a charged colloidal particle driven by a binary monovalent electrolyte concentration gradient in porous media. In this work, we extend our model to consider valence asymmetric electrolytes. The porous medium is modeled as a Brinkman medium with a constant Darcy permeability. The linearized Poisson-Boltzmann equation is invoked to model a weakly or moderately charged particle. We report two new findings. First, regardless of the valence asymmetry of the electrolyte, decreasing the porous media permeability increases the hydrodynamic drag to the particle and lowers the particle mobility. Second, leveraging the large difference in cation and anion diffusivities in some valence-asymmetric electrolytes, the enhancement in the particle diffusiophoretic motion could compensate the reduction due to the porous media. The mathematical developed here could be employed to tailor diffusiophoretic colloid transport in porous media with a wider set of electrolytes, which are central to applications such as nanoparticle drug delivery and enhanced oil recovery.