Novel thin-film composite pervaporation membrane with controllable crosslinking degree for enhanced water/alcohol separation performance

Abstract

Thin-film composite (TFC) pervaporation membranes is of widespread interest for the alcohol dehydration, since the thin selective layer allows a high permeation flux. However, how to obtain the desired flux and separation selectivity simultaneously is still the bottleneck of industrial application with pervaporation technology. In this study, a novel ultrathin multi-layer polyurea or polyamide pervaporation membrane was designed and assembled via layer-by-layer (LBL) interfacial polymerization (IP) method on the hydrolyzed polyacrylonitrile (HPAN) substrate membrane. During the LBL assembly process, the controllable crosslinking degree of the separation layer formed through changing the concentration of the oil phase monomer while remaining the concentration of the aqueous phase monomer constant based on the solution-diffusion mechanism of pervaporation separation process. The surface characterization revealed that the tris(2-aminoethyl) amine (TAEA)1.5-toluene 2,4-diisocyanate (TDI)1-0.5-0/HPAN composite membrane exhibited much rougher surface than that of the membranes with the same crosslinking degree. The optimized composite membrane exhibited a high separation factor of 844.6 with a desirable permeation flux of 1284.3 g·m−2·h−1 for the pervaporation dehydration 95 wt% ethanol aqueous solution at 80 °C, which was 10-fold increase of separation factor compared with the control membrane. Moreover, the excellent operation stability of the TFC membrane demonstrated the promising prospect for the alcohol dehydration separation. This preparation methodology has potential application in other membrane separation process on the basis of solution-diffusion mechanism, such as gas separation and reverse osmosis membrane.