Parallelism and differences of pervaporation and vacuum membrane distillation in the removal of VOCs from aqueous streams

Abstract

In this work two gas–liquid separation processes, pervaporation (PV) and vacuum membrane distillation (VMD), have been compared in their application to the separation of chloroform–water mixtures. After selection of the adequate separation membrane the comparison of the PV and VMD should be based on the kinetics and selectivity towards the desired compound. The kinetic models and parameters previously reported by the authors (A.M. Urtiaga, E.D. Gorri, J.K. Beasley, I. Ortiz, J Membr Sci 156 (1999) 275–291 and A.M. Urtiaga, G. Ruiz, I. Ortiz, J Membr Sci 165 (2000) 99–110) for the separation of chloroform from aqueous solutions in the range of concentrations 200<C<2000 mg/l, temperature 5<T<44°C and flowrate 140<Re<1400 have been used to compare the mass transfer flux and selectivity in both separation processes. The use of hollow fiber membranes of polydimethylsiloxane in the PV system and microporous polypropylene in the VMD process resulted in the same rate of removal in both systems under the simulated conditions. Particularly, the PV system offered the uppermost selectivity, providing a high concentration of chloroform in the permeate.