Ethanol mass transfer during pervaporation with PDMS membrane based on solution-diffusion model considering concentration polarization

Abstract

A mass transfer model of ethanol recovery by pervaporation with polydimethylsiloxane (PDMS) membrane was developed based on solution-diffusion theory considering concentration polarization. The water/polymer interaction parameter, ethanol/polymer interaction parameter, the limiting diffusivity of ethanol and plasticization coefficient of ethanol were determined. The concentration polarization coefficient was calculated based on the convective mass transfer on the upstream of the membrane. The effect of convective mass transfer coefficient, partition coefficient and ethanol diffusion mass transfer in membrane on ethanol flux and concentration polarization coefficient were explored. Partition coefficient of 2.98 and ethanol diffusion mass transfer in membrane of 7.05 × 10−7 m2 s−1 were determined. The concentration polarization coefficient of 0.15 and the ethanol flux of 318 g m−2 h−1 were obtained under the condition of 5 wt% of ethanol feed concentration and convective mass transfer coefficient being 1.23 × 10−5 m2 s−1. Higher convective mass transfer coefficient, higher partition coefficient and higher ethanol diffusion mass transfer in membrane could improve the membrane flux. However, the bad effect of concentration polarization coefficient on ethanol flux was severe if the partition coefficient and ethanol diffusion mass transfer in membrane are higher. The developed model could accurately predict membrane separation, especially under the condition of higher concentration polarization coefficient.