Zeolite A membranes synthesized on a UV-irradiated TiO2 coated metal support: the high pervaporation performance

Titania supported zeolite A membranes (3.5 μm thickness) with very high selectivities (54×103) and fluxes (0.86 kg/(m2 h)) for the pervaporation of water/ethanol mixtures at 45 °C have been synthesized. Their exceptional performance is ascribed to pretreatment of the supporting titania with UV-photons, which improves the hydrophilicity of the support, implying that the amount of surface Ti-OH groups has been increased. The interaction between the zeolite A synthesis gel and the support is, thus, improved and the population of zeolite nuclei on the support surface is increased [Micropor. Mesopor. Mater., in press], leading to an improved membrane quality. Variations in membrane performance are observed for different batches. This can largely be ascribed to extensive flaws in the macroporous supports, leading to large membrane defects. The small defect sizes are controlled by the hydrophilicity of the support surface. At sizes of up to several nanometers, defects are believed to improve the membrane performance, because the flux is increased without significant selectivity loss due to the strong interaction between water molecules and zeolite A surface.