Layer-by-layer assembled nanohybrid multilayer membranes for pervaporation dehydration of acetone–water mixtures

In this article, an organic–inorganic nanohybrid multilayer membranes have been developed by incorporating zirconium dioxide (ZrO2) and alumina oxide (Al2O3) nanoparticles into polyelectrolyte complexes such as poly(diallyldimethyl ammonium chloride)/poly(sodium styrene sulfonate) and poly(ethyleneimine)/polyacrylic acid. These nanohybrid multilayers were successfully formed on to both flat sheets and hollow fiber polyacrylonitrile ultrafiltration support membranes by layer-by-layer (LbL) assembly of polycation- and polyanion-coated nanoparticles and used for pervaporation dehydration of an acetone–water mixture. We show that the matching between the size of the NPs and the supporting membrane pore size strongly influences the morphologies and performance of the multilayer membranes. SEM-EDX and AFM analyses suggest that the ZrO2 NPs are mostly distributed on the substrate surface while the Al2O3 NPs are able to migrate into the substrate membrane pores. This is due to the differences between the sizes of the two NPs and results in an increase of the surface roughness of the ZrO2 nanohybrid multilayer membrane while that of the Al2O3 nanohybrid multilayer membrane decreased. The ZrO2 nanohybrid multilayer membrane was able to overcome the trade-off phenomenon, which enabled both higher flux and larger separation factor. However, for the Al2O3 nanohybrid multilayer membrane, the separation factor increased while the corresponding flux values were somewhat lower than those observed for pristine polymeric membranes.