Formation and consolidation of filter cake in microfiltration of emulsion–slurry

The dynamic behaviors of unstirred dead-end microfiltration were explored under constant pressure conditions using a binary dispersion of oil-in-water (O/W) emulsion and polymethyl-methacrylate (PMMA) slurry, which is referred to as emulsion–slurry. The Ruth filtration coefficient determined from the flux decline data increased steadily during the course of filtration, and then a bilayer filter cake formed composed of the upper emulsion cake and the lower PMMA cake. Each average specific filtration resistance of the emulsion cake and the PMMA cake was well evaluated in terms of the resistance-in-series model in filtration. The PMMA cake was nearly incompressible, while the emulsion cake formed on the PMMA cake was highly compressible. Only the emulsion cake was consolidated without the cake cracking or the coalescence of oil droplets. The compressed cake of gel–emulsion had a porosity that was much lower than that of hexagonal close packing of undistorted spheres because of the remarkable deformation of oil droplets under the action of the compressive pressure. It was clearly demonstrated that the gel–emulsion cake formed in filtration of emulsion–slurry was exactly similar in nature to that formed in filtration of mono-dispersed O/W emulsion.