Sorption and pervaporation of dilute aqueous solutions of organic compounds through polymer membranes

Pervaporation of dilute aqueous binary mixtures of four organic compounds (benzene, chloroform, acetone and ethanol) through nitrile—butadiene and styrene—butadiene copolymers was investigated. A pervaporation device has been built, which allows measurement of the pervaporation flux and selectivity of a membrane as a function of the upstream composition of the feed and the downstream total pressure of the pervaporate. In order to relate pervaporation results to equilibrium properties of the membranes, the sorption of water and dilute aqueous solutions was mainly investigated. The pervaporation of dilute aqueous solutions of benzene and chloroform has been extensively studied, including the separation of traces of chloroform, and is modelled through a “sixcoefficients exponential model” [1]. This model is derived from a solution—diffusion analysis of the selective transfer, assuming an exponential dependence of both diffusivities on concentrations of both permeants. Semi-quantitative information about the potential interactions existing in the system solute i—solvent j—membrane and about the concentration profiles at steady-state may be derived from these coefficients.