Abstract
Colloids are positively or negatively charged, and colloid suspensions are polydispersed in natural systems. In this work, we analytically investigated the diffusion in the binary suspension system of charged spherical colloidal particles. The ratio of the diffusion coefficient of a charged colloidal particle in the binary system calculated by Langevin equation to that of a non-charged colloidal particle in the free medium calculated by Stokes-Einstein relation was evaluated. The dependency of the ratio on the charge, diameter and molar fractionation of the colloidal particle was discussed. The ratio was found to be less than unity. This means that the diffusion of a charged colloidal particle is slowed down through the friction induced on the colloidal particle by the electrostatic interaction. It was found that the ratio does not depend on the charge and diamter when the molar fractionation of the charged colloidal particle is large, but that the ratio decreases as the charge and diamter of the charged colloidal particle decreases when the molar fractionation is small.
