Asymmetric TiO_2 hybrid photocatalytic ceramic membrane with porosity gradient: Effect of structure directing agent on the resulting membranes architecture and performances

摘要

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 Ml 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.