Fabricating thin-film composite membranes for pervaporation desalination via photo-crosslinking

Abstract Pervaporation (PV) is a low-energy membrane separation technology widely studied for desalination, water treatment and solvent recovery where heat is applied to vaporize the feed solution and a vacuum is applied at the permeate side to drive the separation of miscible mixtures. The heart of this technology – polyvinyl alcohol (PVA) that is commonly used as the separation layer of polymer membranes is often fabricated over long cross-linking durations, high temperatures or toxic cross-linkers to prevent it from being dissolved in water. Here we overcome these intrinsic material limitations with a photo-crosslinkable polymer, poly(vinyl alcohol)-stilbazol quaternized (PVA-SBQ), commonly deployed in the printing industry, as the dense selective layer of a thin-film composite PV membrane. The separation performances of the resultant PVA-SBQ/nanofiber thin-film composite membranes were optimized as a function of photo-crosslinking conditions where ultra high water fluxes of 122.6 ± 10.8 kg·m−2·h−1 were achieved while desalinating 3.5 wt% NaCl from water at 75 °C and a permeate pressure of 100 Pa. This high PV desalination performance was also maintained during brine (containing 10 and 20 wt% of NaCl) treatment.