Alumina and titania multilayer membranes for nanofiltration: preparation, characterization and chemical stability

Abstract The preparation and characterization of porous ceramic multilayer nanofiltration (NF) membranes is described. During preparation, special care was given to each sub-layer that forms a part of the multilayer configuration: the macroporous substrate, the membrane interlayers and the NF toplayers. High-quality macroporous supports are prepared from α-Al 2 O 3 . Three types of colloidal sol–gel derived mesoporous interlayers are considered: Al 2 O 3 , TiO 2 and mixed Al 2 O 3 –TiO 2 . The active NF toplayer is a very thin and fine textured polymeric TiO 2 toplayer. Optimized α-Al 2 O 3 /γ-Al 2 O 3 /anatase and α-Al 2 O 3 /anatase/anatase multilayer configurations show high retentions for relatively small organic molecules (molecular weight cut-off 2 O 3 layers is restricted to mild aqueous media (pH 3–11) or non-aqueous media (organic solvents). For NF applications in aqueous media with a lower or higher pH, the multilayer membrane composed of anatase on a α-Al 2 O 3 support is to be preferred.