| Abstract
| - On the basis of the standard theory of the primary electroviscous effect in a moderately concentrated suspensionof charged spherical particles in an electrolyte solution presented by Ruiz-Reina et al. (Ruiz-Reina, E.; Carrique, F.;Rubio-Hernández, F. J.; Gómez-Merino, A. I.; García-Sánchez, P. J. Phys. Chem. B2003, 107, 9528), which isapplicable for the case where overlapping of the electrical double layers of adjacent particles can be neglected, thegeneral expression for the effective viscosity or the primary electroviscous coefficient p of the suspension is derived.This expression is applicable for a suspension of spherical particles of radius a carrying arbitrary zeta potentials ζat the particle volume fraction φ ≤ 0.3 for the case of nonoverlapping double layers, that is, at κa> 10 (where κis the Debye−Hückel parameter). A simple approximate analytic expression for p applicable for particles with largeκa and arbitrary ζ is presented. The obtained viscosity expression is a good approximation for moderately concentratedsuspensions of the particle volume fraction φ ≤ 0.3, where the relative error is negligible for κa ≥100 and even atκa = 50 the maximum error is ∼20%. It is shown that a maximum of p, which appears when plotted as a functionof the particle zeta potential, is due to the relaxation effect as in the case of the electrophoresis problem.
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