Diffusiophoresis of Concentrated Suspensions of Spherical Particles with Charge-regulated Surface: Polarization Effect with Nonlinear Poisson−Boltzmann Equation

Abstract

Diffusiophoresis in concentrated suspensions of spherical colloids with charge-regulated surface is investigated theoretically. The charge-regulated surface considered here is the generalization of conventional constant surface potential and constant surface charge density situations. Kuwabara's unit cell model is adopted to describe the system and a pseudospectral method based on Chebyshev polynomial is employed to solve the governing general electrokinetic equations. Excellent agreements with experimental data available in literature were obtained for the limiting case of constant surface potential and very dilute suspension. It is found, among other things, that in general the larger the number of dissociated functional groups on particle surface is, the higher the particle surface potential, hence the larger the magnitude of the particle mobility. The electric potential on particle surface depends on both the concentration of dissociated hydrogen ions and the concentration of electrolyte in the solution. The electric potential on particle surface turns out to be the dominant factor in the determination of the eventual particle diffusiophoretic mobility. Local maximum of diffusiophoretic mobility as a function of double layer thickness is observed. Its reason and influence is discussed. Corresponding behavior for the constant potential situation, however, may yield a monotonously increasing profile.

Electrodiffusiophoresis: Particle motion in electrolytes under direct current

“…15 One of the electrokinetic phenomena that has never been investigated with polarizable surfaces is diffusiophoresis, where a charged colloidal particle moves under the action of a gradient of electrolyte concentration, and the related phenomenon of diffusio-osmosis, consisting of the flow of liquid with respect to a stationary charged surface, 16 realized that a gradient of electrolyte concentration could induce motion and provided the first theory of this effect. 17 Over the past few decades, a number of theoretical and experimental advances have been made, 18,19 and diffusion-driven motion is now an active field of research, [20][21][22][23] with results available for arbitrary values of the zeta potential, Debye length, particle size, and even volume fraction of solids.…”

Diffusiophoresis of a polyelectrolyte in a salt concentration gradient

“…The spontaneous movement of charged colloids in an electrolyte solution subject to an applied salt gradient, known as diffusiophoresis , has been studied recently by many investigators both theoretically and experimentally . Compared to conventional electrophoresis operations, diffusiophoresis has the advantages such as no Joules heat effect and metals in electrical contact .…”

Influence of membrane layer properties on the electrophoretic behavior of a soft particle

“…Suppose that the surface of the core of a soft particle is maintained at a constant charge density of σ p =2ε 1 ε 0 ζ/ a =1.182×10 −3 C/m 2 and its membrane layer is uncharged ( n fix0 =0). This type of surface charged conditions 35 is capable of modeling a surface having reactive functional groups with an extremely slow rate of reaction 54. In the present case, ζ p is a function of κ a , ( c/a ), and ε fix .…”