Highly selective PDMS-PVDF composite membrane with hydrophobic crosslinking series for isopropanol-1,5 pentanediol pervaporation

An energy-efficient pervaporation (PV) facile approach was designed to remove isopropanol during α, ω-diol production. Accordingly, a series of polydimethyl siloxane (PDMS) membranes were prepared by tuning their surface chemistry through trifunctional (PFTES and OTMS) and traditional tetrafunctional (TEOS) crosslinkers and casting on a polyvinylidene fluoride (PVDF) membrane. Additional hydrophobic tail enrichment on the membrane surface because of alkyl (OTMS) and fluoroalkyl (PFTES) groups from the tri-functional crosslinker was confirmed by FTIR, XPS, and DSC. TGA and XRD revealed that the tetra crosslinking site promoted a denser structure across the membrane than the trifunctional crosslinker. In the water contact angle measurements of the different series of membranes, the contact angle was proportional to the hydrophobic site. When a series of PDMS membranes were tested for PV of the novel feed PDO/IPA (90/10 w/w) system, the highest flux was delivered from the fluoroalkyl type crosslinked membrane, which was attributed to its superior hydrophobicity and amorphous nature, with excellent IPA selectivity from all the membranes. As a result, a stabilized flux of 235.8 g/m2h and excellent separation factor (IPA content in permeated >99.95%) in a 40 h continuous PV test was achieved using the PDMS PFTES membrane.