Cross-flow microfiltration (CFMF), is a process for separation of larger size solutes from aqueous solutions by means of a semi-permeable membrane passed over the filtration medium. Clear liquid permeates the filtration medium and is recovered as the permeate, while the solids accumulate at the filtration barrier to form a fouling layer, or cake. The cake, constituting an increase in hydraulic resistance, decreases the permeate flux.
However, the tangential suspension flow tends to limit the growth of the cake. Thus, after an initial rapid increase in cake thickness, cake growth ceases, and the cake thickness becomes limited to some steady-state value. Correspondingly, after an initial rapid decrease, the permeate flux levels off and either attains a steady-state, or exhibits a slow, long-term decline with time. Microfiltration is suited to separate larger sizes, such as suspended solids, particulates, and microorganisms.
This is accomplished because microfiltration membranes are thought to act like a physical seive. The membranes are highly porous and have discernible pores even when the surface skins are asymetric. Therefore, the separation is based mainly on size. Membrane material is usually made up of ceramics, teflon, polypropylene, or other plastics.