Influence of inorganic salts on pervaporation performance of PDMS/ceramic composite membranes

There are many significant advantages when pervaporation is used in the separation of ethanol/water system. The current studied systems are mainly the binary feed mixtures, but the real systems are commonly multi-component mixtures and might include inorganic salts and sugars, which may have effects on the pervaporation performance of the membrane. In this work the effects of three inorganic salts (NaCl, KCl and MgCl₂) on the pervaporation performance of polydimethylsiloxane (PDMS)/ceramic composite membranes were studied. The results showed that the addition of inorganic salts caused simultaneously the increase of the flux and the separation factor. Among the three salts, MgCl₂ had the most notable effect on the pervaporation performance. The separation factors of the tertiary system were 2.8, 2.5 and 2.4 times of those of the ethanol/water binary system for MgCl₂, NaCl and KCl respectively. The experimental phenomena could be explained by the ethanol activity, which was calculated by using the Setschenow empirical equation.