Structure regulation of PDMS coating on PTFE membrane surface to achieve efficient separation of gaseous peppermint aromatic water.

[Display omitted] • A PDMS coated PTFE separation membrane for gaseous aromatic water was explored. • Effective separation properties of the prepared PDMS/PTFE membranes were found. • The medicinal components of the obtained essential oils meet the EP standard. • Membrane separation mechanism of gaseous peppermint aromatic water was revealed. This study harnessed polydimethylsiloxane (PDMS)-coated polytetrafluoroethylene (PTFE) composite (PDMS/PTFE) membranes for the separation of peppermint aromatic water in vapor state. The effects of the PDMS coatings' morphology structure on the separation performance of the membrane were investigated. The vapor permeation process, selective-permeation mechanism, and membrane stability were explored. Results showed that the separation effect of the membranes depended on the degree of polymerization of PDMS coating. Almost no water molecules can pass through the membrane during the 6 h separation process, and the separation factor was as high as 668. The main pharmacodynamic components in the separated permeate were L-menthol, L-menthone, and menthyl acetate, accounting for 49.16 %, 26.3 %, and 5.46 %, respectively, which conformed to the standard of the European Pharmacopoeia. The parameters of membrane separation showed that the maximum permeability coefficients of L-menthol, L-menthone, menthyl acetate, and water were 40.80, 20.28, 4.211, and 0.3945, respectively, at 105 °C and 65 kPa. This finding indicated that the large difference in permeability coefficient was the key to the excellent selectivity of the PDMS/PTFE membrane for separating volatile pharmaceutical components and water molecules in the peppermint aromatic-water system. [ABSTRACT FROM AUTHOR]