Pervaporation:

Pervaporation is a membrane separation process whereas a membrane separates liquid feed and vapour permeates phases. A few of the components within the liquid feed phase vapourises and permeates by the membranes and separation includes a phase modification. A schematic of pervaporation process is provided in Figure.

Figure:  A schematic representation of pervaporation process

It is a versatile technique of separation of polar and nonpolar liquid mixtures and the driving force for this type of separation is the partial pressure difference of the permeating elements across the membranes. The gaseous permeate is commonly held at a low pressures and the liquid feed stream is at an elevated temperature to facilitate evaporation of permeating elements. Pervaporation is an attractive procedure for separation of liquid mixtures that form azeotropes, that is, where vapour and liquid have the similar composition in equilibrium and standard distillation cannot achieve the separation. Significant applications of pervaporation procedure are dehydration of alcohol and recovery and concentration of naturally occurring aroma elements from dilute solutions.