Well-organized, mesoporous nanocrystalline TiO₂ on alumina membranes with hierarchical architecture: Antifouling and photocatalytic activities

We report the development of improved antifouling and photocatalytic membranes based on an organized mesoporous TiO₂ (om-TiO₂) layer on a porous alumina (Al₂O₃) support. The om-TiO₂ layer was templated by an amphiphilic graft copolymer, i.e., poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), and was 50–70 nm in pore size with high porosity and good pore interconnectivity. The precoating of poly(vinyl pyrrolidone) (PVP) on a porous alumina support was the key to providing a flat platform and improving the adhesion properties of alumina with TiO₂, which allowed for the formation of om-TiO₂ membranes. Fouling of photocatalytic om-TiO₂ on the alumina membrane was also investigated using a laboratory-scale photocatalytic dead-end filtration reactor using a model dye compound. The fouling rate was observed to be much slower for the om-TiO₂ membrane compared to the bare alumina support under UV illumination during 6 h of membrane operation. The PVP precoating on the alumina support improved the permeation quality of the om-TiO₂ membrane. The improved removal of the organic dye compound was thought to result from the enhanced adsorption capability of organic compounds and subsequent photocatalytic reactions on the om-TiO₂ layer. However, UV illumination performed for longer than 6 h gradually increased the fouling rate due to the deposition of the organic dye compound on the membrane surface, and prohibited the accessibility of the UV light to the TiO₂ layer.