Numerical Analysis of the Concentration Polarization in Colloidal Suspensions: Comparison with Theoretical Predictions

Abstract

The equation system based on the standard model for a charged spherical particle suspended in an electrolyte solution and under the action of a static applied field is numerically solved. Equilibrium and nonequilibrium properties—electric potential, ion concentrations, adsorption coefficients, dipolar coefficient, stored electrostatic and Gibbs free energies, conductivity increment, and permittivity increment—are deduced, discussed, and compared with theoretical predictions of the Shilov and Dukhin model. Theoretical predictions for the conductivity properly reproduce the numerical results for low values of the surface potential. But for highly charged particles important deviations appear even for large particle radius to Debye screening length ratios. Theoretical predictions for the permittivity are generally better than for the conductivity. This leads to the conclusion that in many situations the theoretical expression is sufficiently good for the interpretation of experimental results in terms of the standard model. But its range of applicability is determined not only by the particle radius to Debye screening length ratio but also by the surface potential.