Most industrial scale separation processes are basedon energy intensive methods such as distillation, evaporation,and freeze crystallization. Membrane separationsoffer significant advantages over existing separation processes.Current membrane separation technologies canoffer energy savings, low-cost modular construction, highselectivity of separated materials, and processing of temperature-sensitive products [1-5]. Membranes separatemixtures by discriminating the components on the basisof physical or chemical attributes, such as molecular size,charge, or solubility [6]. By passing water and retainingsalts, membranes are used to produce over half of theworld's desalinized potable water. Membranes can alsoseparate oxygen and nitrogen from air as well as hazardousorganics from contaminated water in applicationssuch as groundwater remediation.The need for membrane separation technology increasesas environmental requirements tighten, water circuitsclose, the recycling of wastes increases and the purityrequirements for foodstuff and pharmaceuticals increase.Six major membrane processes (microfiltration,ultrafiltration, reverse osmosis, electrodialysis, gas separationand pervaporation) have found use in such applicationareas as water purification, chemical and food processing,drug delivery, bioseparations, and medical treatment[1-6].This present paper reviews pervaporation and vaporpermeation - two particularly useful and relatively newmembrane separation processes.
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