A model for the viscosity of dilute smectite gels

A simple yet accurate model describing the viscosity of dilute suspensions of sodium montmorillonite in dilute homoionic solutions is presented. Taking the clay particle and the surrounding clouds of ions as a whole as an uncharged but soft, coin-like particle, the Huggins’ equation for a suspension of uncharged particles is extended in the model to account for not only the primary and the secondary electroviscous effects, but also the multi-particle interaction. The agreements between the predicted and measured results are excellent. The Huggins’ coefficient obtained compares favorably with available data, while the intrinsic viscosity reduces to the Simha’s equation in the large limit of ionic strength, suggesting that the model is robust.

► We develop a dressed-ion model describing the viscosity of dilute smectite gel in homoionic solutions.
► We take the clay particle and the surrounding clouds of ions as a whole as an uncharged but soft, coin-like particle.
► We extend the Huggins’ equation to account for both the electroviscous effects and the multi-particle interactions.
► The agreements between the predicted and measured viscosity of the Na-montmorillonite suspensions are excellent.