Properties of a Filter Cake Formed in Dead-End Microfiltration of Colloidal Particles Suspended in Aqueous Organic Solvents

Abstract

Microfiltration experiments were conducted using TiO2 particles suspended in aqueous methanol, ethanol, t-butanol, and acetone solvents of various concentrations. Filtration behaviors were examined in terms of the average specific filtration resistance and the average porosity of the filter cake formed on the membrane surface. Such properties of the filter cake were strongly dependent on the sort of organic solvent used, and the concentration and pH of the aqueous organic solvent. The results indicate that the electric nature of particles controlled via changes in the solution environment plays a significant role in determining the structure of the filter cake which, in turn, influenced the filtration rate in microfiltration of colloidal particles suspended in aqueous organic solvents. The experimental results were analyzed based upon a DLVO theory which considered the balance between the electrostatic repulsion and the attraction. The concept of the coagulation parameter derived based upon the DLVO theory has been introduced to evaluate the degree of the coagulation and the dispersion of the systems, and to elucidate the filtration behaviors of the colloidal particles suspended in the aqueous organic solvents. In addition, it was shown that in the dispersion range the coagulation parameter was closely related to the stability ratio.