Ultrafiltration (UF or UF/DF) is a unit operation that separates large solutes from small solutes and solvents. Larger pore membranes are referred to as microfiltration (MF), while smaller pore filters are referred to as reverse osmosis (RO). There is some nomenclature confusion as membrane scientists refer to a loose RO charged membrane as a nanofilter, while bioprocessors refer to a loose UF membrane as a nanofilter that removes nanometer-sized viruses.
UF employs thin porous solid UF membranes as either flat sheets or tubes (see chapter “ UF Membranes (Ultrafiltration Membranes)”). These perform separations by retaining and passing solutes primarily based on their size and secondarily based on solute-surface interaction by charge or other fields (see chapter “ UF Transport (Ultrafiltration Transport)”). Pressures of 0.2–1.0 MPa drive liquid solvents (primarily water) through the membrane. Since retained solid buildup can cause the solute flow to rapidly decline, most UF systems are...
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