Diffusiophoresis of a Charged Particle in a Charged Cavity with Arbitrary Electric-Double-Layer Thickness

• Main Authors: Ya-Ching Chiu, 邱雅晴
• Other Authors: 葛煥彰
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/ufr282

碩士 === 國立臺灣大學 === 化學工程學研究所 === 106 === An analytical study is presented for the diffusiophoretic motion of a charged colloidal sphere located at the center of a charged spherical cavity filled with an electrolyte solution at the quasisteady state for the case of arbitrary electric double layers. The electrokinetic equations governing the ionic concentration, electric potential, and velocity distributions in the fluid phase are linearized by assuming that the system is only slightly distorted from equilibrium. These linearized equations are solved by using a perturbation method with the zeta potentials of the particle and cavity as the small perturbation parameters. An explicit formula for the diffusiophoretic velocity of the particle as a combination of the electrophoretic and chemiphoretic contributions valid for arbitrary values of and is obtained from a balance between the electrostatic and hydrodynamic forces acting on it, where is the Debye screening parameter, is the radius of the particle, and is the radius of the cavity. The effect of the charged cavity wall on the diffusiophoresis of the particle is interesting and can be significant. The contributions from the diffusioosmotic (electroosmotic and chemiosmotic) flow occurring along the cavity wall and from the wall-corrected diffusiophoretic driving force to the particle velocity are equivalently important, and this diffusioosmotic flow can reverse the direction of the particle velocity, which in general increases with an increase in and decreases with an increase in , but exceptions exist.