ABSTRACT
Filtration is the operation of separating a dispersed phase of solid particles from a fl uid by means of a porous fi lter medium, which permits the passage of the fl uid but retains the particles. Filtration is probably one of the oldest unit operations. The old forms of fi ltration by straining through porous materials were described by the earliest Chinese writers. A gravity fi lter used in a chemical process industry was described in an Egyptian papyrus which has its origin in about the third century a.d. In recent years, many developments have increased the application of fi ltration. Filtration steps are required in many important processes and in widely divergent industries. The importance of fi ltration technique has been emphasized by the increased need for protection of the environment. Recently, membrane fi ltration of colloids has become increasingly important in widely diversifi ed fi elds.
