Transmission of butanol isomers in pervaporation based on series resistance model

Abstract Pervaporation (PV) has shown great potential in the separation of butanol aqueous solutions due to their economic and environmental benefits. This work applies polydimethylsiloxane (PDMS) composite membrane to separate four butanol isomers (n-butanol, isobutanol, sec-butanol and tert-butanol) in aqueous solution. Based on physical and chemical properties of butanol isomers, such as solubility, polarity and interaction parameter, we systematically study the transmission difference in the pervaporation process. The influence of feed concentration, temperature and permeate pressure on membrane performance of PDMS composite membrane are investigated. The results show that the contact angles of butanol isomers on the PDMS layer are 51°, 42.7°, 37.7°, 29.1° and the fluxes at 40 °C are 237.6 g m-2 h-1, 245.4 g m-2 h-1, 224.1 g m-2 h-1, 169.4 g m-2 h-1 for n-butanol, isobutanol, sec-butanol, and tert-butanol, respectively. Moreover, the similar compatibility principle is introduced to the series resistance model so the process simulation matches well with the antagonistic effect of water molecules on mass transfer of butanol isomers. The permeation activation energy is negative, indicating that the dissolution dominates the dissolution and diffusion process. In addition, low vacuum is not conducive to the separation of n-butanol from water. The research on isomers separation through pervaporation may pave a way to separate other solvents of similar properties.