Semi-permeable membranes - Pervaporation membranes

A pervaporation membrane is a non-porous, organic, anisotropic (asymmetric) or composite artificial membrane.

In all cases, the active layer is a dense, glassy polymer or elastomer layer less than 0.1 µm thick. In the case of composite membranes, this active layer is supported by one or more more porous, mechanically stronger layers, the whole having a thickness of around 100 µm.

Pervaporation membranes were originally developed to perform liquid pervaporation (perdistillation), an operation in which the upstream face of the membrane is bathed by the solution to be treated, while its downstream face is in contact with the extracted vapour that has passed through it. In the case of vapor pervaporation membranes, both sides of the membrane are in contact with vapors, the one to be treated and the one extracted, which makes them similar to gas permeability membranes.