Pervaporation is subjected to a vacuum on one side of the membrane, so readily permeable component evaporates from the side, causing a concentration gradient in the solution of the other side. Thereby driving component separation. Pervaporation is a combination of organic matter to dissolve - diffusion mechanism through the membrane permeation evaporation process and volatiles. Selectively determined by an organic liquid membrane material affinity, molecular size, and vapor pressure. For different situations, these three factors in one or two plays a leading role. For amorphous polymers, permeability depends mainly on the diffusion of molecules, the size and form of the molecule. Therefore pervaporation process can be used to separate azeotropes and isomers thereof.
Since polyimide has a high temperature, the working temperature can be increased. Chemical stability, various compounds may be isolated. While there are a high separation factor and therefore have great potential applications in pervaporation aspects. However, due to pervaporation own limitations, as operated under vacuum conditions, typically using recycled components vaporized liquid nitrogen or dry ice condensation. If you want to recycle cheap ingredients such as lower alcohols, hydrocarbons, chlorinated hydrocarbons, etc., cost recovery is an issue that must be considered. So far the use of pervaporation technology more for organics - water system, because the water does not need to be recycled.