Nanocrystalline TiO₂ Photocatalytic Membranes with a Hierarchical Mesoporous Multilayer Structure: Synthesis, Characterization, and Multifunction

Abstract

A novel sol–gel dip‐coating process to fabricate nanocrystalline TiO2 photocatalytic membranes with a robust hierarchical mesoporous multilayer and improved performance has been studied. Various titania sols containing poly(oxyethylenesorbitan monooleate) (Tween 80) surfactant as a pore‐directing agent to tailor‐design the porous structure of TiO2 materials at different molar ratios of Tween 80/isopropyl alcohol/acetic acid/titanium tetraisopropoxide = R:45:6:1 have been synthesized. The sols are dip‐coated on top of a homemade porous alumina substrate to fabricate TiO2/Al2O3 composite membranes, dried, and calcined, and this procedure is repeated with varying sols in succession. The resulting asymmetric mesoporous TiO2 membrane with a thickness of 0.9 μm exhibits a hierarchical change in pore diameter from 2–6, through 3–8, to 5–11 nm from the top to the bottom layer. Moreover, the corresponding porosity is incremented from 46.2, through 56.7, to 69.3 %. Compared to a repeated‐coating process using a single sol, the hierarchical multilayer process improves water permeability significantly without sacrificing the organic retention and photocatalytic activity of the TiO2 membranes. The prepared TiO2 photocatalytic membrane has great potential in developing highly efficient water treatment and reuse systems, for example, decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and self‐antifouling action because of its multifunctional capability.

Mesoporous titania photocatalysts: preparation, characterization and reaction mechanisms

“…The most commonly used organic templates were amphiphilic poly(alkylene oxide) block copolymers, such as HO-(CH 2 CH 2 O) 20 (CH 2 CH(CH 3 )O) 70 ( 17 and cetyltrimethylammonium bromide (CTAB) ( Table 1). [29][30][31][32]43,[45][46][47]87,100 TiO 2 is an interesting material for photocatalytic applications and it is regarded as the most efficient and environmentally benign photocatalyst, and it has been most widely used for photodegradation of various pollutants such as methylene blue (MB), 30,37,52,55,57 methyl orange (MO), 30,39 Escherichia coli (E. coli), 57,60 Rhodamine B (RhB) 36,[46][47][48] Rhodamine 6G (Rh6G) 29 and phenol 27,47 (Table 1). The principle of the semiconductor photocatalytic reaction is straightforward.…”

“…57 The prepared TiO 2 photocatalytic membrane has great potential in developing highly efficient water treatment and reuse systems, for example, decomposition of organic pollutants, inactivation of pathogenic microorganisms, physical separation of contaminants, and self-antifouling action because of its multifunctional capability. Wang et al, 58 have obtained 3D ordered mesoporous sulfated-TiO 2 reacting a cubic mesoporous amorphous TiO 2 film with sulfuric acid at high temperature to produce sulfur-containing mesoporous TiO 2 with nanocrystalline frameworks.…”

Structural Characterization and Photocatalytic Activity of Hydrothermally Synthesized Mesoporous TiO2 for 2,4,6-Tribromophenol Degradation in Water

“…the titanium source, acid catalyst, and ligand complexation reagents, etc. Among these methods, the sol-gel procedure is the simplest method to prepare M-TiO 2 , which can be used with [10][11][12][13][14] or without [15,16] addition of structural directing reagents. In fact, the utilization of templates allows the forming of long-ranged 3D nanosize network materials with a well defined mesoporous structure [17,18].…”

“…However, the synthesis of M-TiO 2 is still a challenge due to difficulties in the rapid optimization of the synthesis conditions such as the method and parameters [8][9][10][11][12][13], e.g. the titanium source, acid catalyst, and ligand complexation reagents, etc.…”

Composites, Multifunctional

“…These properties make bone a reliable biological structural material. Bone is considered as a nanocomposite of minerals and proteins [18,26]: It is composed of a ma trix impregnated with calcium carbonate, calcium sul phate and small amounts of sodium and magnesium. The matrix, consist of collagen fibers impregnated with crystals of hydroxyapatite, Ca 5 (PO 4 ) 3 (OH), and water.…”