1. Introduction
Photocatalytic technologies for environmental purification have been developed to eliminate refractory organic contaminants [1] and [2]. Yet, the use of aqueous suspensions of photocatalysts in practical applications is limited, because they require separation following treatment. Considerable work has been performed to develop immobilized TiO2 catalysts on various substrates, such as thin films and membranes, for use in many applications [3]. The photocatalytic activity of immobilized TiO2, however, is low due to exfoliation of the deposited TiO2 thin film and to reductions in the effective surface area that is to be illuminated [4].
Incorporation of TiO2 or other radical-generating materials into membranes to reduce membrane fouling has been examined to a limited extent [5] and [6]. The catalytic efficiency and long-term durability of catalyst-polymeric membrane composites tend to counteract each other, wherein efficient hydroxyl radical production leads to degradation of the polymer matrices that embed the catalysts, such as TiO2.
Inorganic membranes overcome this limitation and have been fabricated from preformed TiO2 structures and as composites of TiO2 and ceramic materials [7] and [8]. In this study, we make advances in fabricating such materials by creating catalytic membranes that have a highly ordered structure that complements the advantages of photocatalysis and membrane filtration technologies, using an anodization method to develop nanostructured photocatalytic TiO2 metal membranes.
1. IntroductionPhotocatalytic technologies for environmental purification have been developed to eliminate refractory organic contaminants [1] and [2]. Yet, the use of aqueous suspensions of photocatalysts in practical applications is limited, because they require separation following treatment. Considerable work has been performed to develop immobilized TiO2 catalysts on various substrates, such as thin films and membranes, for use in many applications [3]. The photocatalytic activity of immobilized TiO2, however, is low due to exfoliation of the deposited TiO2 thin film and to reductions in the effective surface area that is to be illuminated [4].Incorporation of TiO2 or other radical-generating materials into membranes to reduce membrane fouling has been examined to a limited extent [5] and [6]. The catalytic efficiency and long-term durability of catalyst-polymeric membrane composites tend to counteract each other, wherein efficient hydroxyl radical production leads to degradation of the polymer matrices that embed the catalysts, such as TiO2.Inorganic membranes overcome this limitation and have been fabricated from preformed TiO2 structures and as composites of TiO2 and ceramic materials [7] and [8]. In this study, we make advances in fabricating such materials by creating catalytic membranes that have a highly ordered structure that complements the advantages of photocatalysis and membrane filtration technologies, using an anodization method to develop nanostructured photocatalytic TiO2 metal membranes.
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