Asymmetric TiO2 hybrid photocatalytic ceramic membrane with porosity gradient: Effect of structure directing agent on the resulting membranes architecture and performances

Abstract Asymmetric TiO 2 hybrid photocatalytic ceramic membranes with porosity gradient have been fabricated via acid-catalyzed sol–gel method. Different structure directing agents (SDAs) i.e. Pluronic P-123, Triton X-100, Tween 20 and Tween 80 were incorporated in the preparation of TiO 2 sol to obtain a porous multilayered TiO 2 coated on the alumina ceramic support. Six different SDA-modified membrane specimens were fabricated. Four of which were coated with the TiO 2 sols prepared using only one type of SDA. The remaining two specimens were fabricated via multilayer coating of different TiO 2 sols prepared using different types of SDAs. Physico-chemical and morphological properties of different TiO 2 layers were thoroughly investigated. The membrane M1 which had the most porous TiO 2 sub-layers showed a high pure water permeability of 155 L m −2 h −1 bar −1 . The membrane showed a relatively high Rhodamine B (RhB) removal of 2997 mg m −2 over 8 h treatment duration in the batch photoreactor, second only to the Pluronic-based TiO 2 membrane (specific RhB removal of 3050 mg m −2 ). All membrane specimens exhibited good performances while operated in the flow-through photocatalytic membrane reactor. Over 91% of RhB removal capability was retained after 4 treatment cycles. All membranes also showed self-cleaning property by retaining >90% of initial flux after 4 treatment cycles. The flexibility of optimizing membrane performances by fine-tuning the porosity gradient configuration of the photocatalytic layer has also been demonstrated.