Filtration Behavior of Suspensions of Uniform Polystyrene Particles in Aqueous Media

Abstract

Cake filtration experiments of suspensions of polystyrene particles, of uniform morphology, through Nuclepore membranes having uniform pores were carried out. The effects of particle properties (size and surface charge), suspension properties (particle concentration and ionic strength), and applied pressure were determined. The results were analyzed in terms of the conventional Darcy-Ruth filtration equation. Plots of resistance versus weight of solids in the cake revealed two distinct regions with a transition occurring early on in the filtration process at a cake thickness of the order of 1 mm. The initial portion has a lower average slope (specific resistance) than that of the second region. It is by only plotting this second region (i.e. ignoring the initial stages of the filtration process) that apparent negative values for the medium resistance are obtained.

The specific cake resistance obtained from the slope of the second region, which spans at least 90% of the filtration time, was correlated with particle and dispersion properties. The specific filtration resistance was essentially independent of slurry concentration and of the total applied pressure. Specific cake resistance measured at constant pressure and slurry concentration showed an inverse dependence on ionic strength.