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Nanocrystalline TiO 2 Photocatalytic Membranes with a Hierarchical Mesoporous Multilayer Structure: Synthesis, Characterization, and Multifunction
Author(s) -
Choi H.,
Sofranko A. C.,
Dionysiou D. D.
Publication year - 2006
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200500658
Subject(s) - materials science , photocatalysis , mesoporous material , chemical engineering , membrane , calcination , coating , porosity , nanocrystalline material , dip coating , superhydrophilicity , anatase , sol gel , biofouling , nanotechnology , composite material , organic chemistry , catalysis , contact angle , chemistry , biology , engineering , genetics
A novel sol–gel dip‐coating process to fabricate nanocrystalline TiO 2 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 TiO 2 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 TiO 2 /Al 2 O 3 composite membranes, dried, and calcined, and this procedure is repeated with varying sols in succession. The resulting asymmetric mesoporous TiO 2 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 TiO 2 membranes. 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.