Morphology-Dependent Dye-Removal Mechanism as Observed for Anatase-Titania Photocatalyst
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Morphology-Dependent Dye-Removal Mechanism as Observed for Anatase-Titania Photocatalyst K. V. Baiju Æ S. Shukla Æ S. Biju Æ M. L. P. Reddy Æ K. G. K. Warrier
Received: 22 March 2009 / Accepted: 4 May 2009 / Published online: 27 May 2009 Springer Science+Business Media, LLC 2009
Abstract Nanotubes of anatase-titania with very high specific surface-area have been synthesized via hydrothermal using the as-received powder of anatase-titania particles, having lower specific surface-area, as a precursor. Various analytical techniques have been used to characterize the as-received powder and hydrothermally processed nanotubes of anatase-titania for their morphology, size, structure, specific surface-area, pore size distribution, photoabsorption, and photoluminescence properties. The dye adsorption and photocatalytic activity of as-received powder and nanotubes of anatase-titania have been studied using the methylene blue as a model catalytic dye agent. It has been shown that, due to higher specific surface-area, the dye removal using the nanotubes of anatase-titania is primarily via surface-adsorption mechanism in the dark; while, that using the anatase-titania particles is via photocatalytic degradation mechanism under ultraviolet-radiation exposure. Hence, the mechanism of dye removal from an aqueous solution using the anatase-titania appears to be highly morphology-dependent. K. V. Baiju S. Shukla (&) K. G. K. Warrier Ceramic Technology Department, Materials and Minerals Division (MMD), National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR), Industrial Estate P.O., Pappanamcode, Thiruvananthapuram, Kerala 695019, India e-mail: [email protected] S. Biju M. L. P. Reddy Chemical Sciences and Technology Division (CSTD), NIIST-CSIR, Thiruvananthapuram, Kerala 695019, India Present Address: K. V. Baiju Catalysis Center, Department of Civil and Environmental Engineering, Northwestern University, Sheridan Road, Evanston, IL 60208, USA
Keywords Anatase Dye adsorption Hydrothermal Nanotubes Photocatalysis Titania
1 Introduction Nanotubes of anatase-titania (TiO2) processed via different approaches including anodization, hydrothermal, and template-based techniques have been investigated for variety of potential industrial applications including lithium-ion storage [1], photovoltaic cells [2], gas sensors [3], direct oxidation methanol fuel cell [4], proton conductor [5], solar energy [6], and photocatalysis [7–9]. Among all these synthesis techniques, the nanotubes of TiO2 processed via hydrothermal technique are of major significance since this is the only technique, which allows the processing of bulk quantity of substrate-free nanotubes of TiO2 having the anatase-structure with nearly 100% yield. The formation mechanism of TiO2 nanotubes during the hydrothermal process involves an exfoliation of single-layer nanosheets from the bulk-TiO2 in a highly alkaline solution and their subsequent rollup to form nanotubes during
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