Membrane filtration retention capacity

A major alternative to direct flow membrane filtration is depth filtration, in which particles are removed throughout the filtration matrix rather than just at the membrane surface, by various mechanisms such as size exclusion, electrostatic, and hydrophobic interactions. Depth filters are typically composed of a bed of cellulose or polypropylene fibers together with an inorganic filter aid such as diatomaceous earth and a binder to form a filter sheet. The filter aid imparts the matrix very high surface areas and plays an important role in increasing both retention and the capacity. Depth filters can also have an electrostatic charge usually associated with the binder polymer. 

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