Photocatalytic properties of rutile TiO 2 acicular particles in aqueous 4-chlorophenol solution
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Jong-Kuk Lee and Eun Gu Lee Department of Materials Engineering, Chosun University, KwangJu 501-759, Korea
Hee-Gyoun Lee IGC-SuperPower, 450 Duane Avenue, Schenectady, New York 12304
Seon-Jin Kim and Kyoung Sub Lee Division of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea (Received 20 March 2002: accepted 2 January 2003)
The photocatalytic properties of TiO2 rutile powder with acicular primary particles were characterized using the photocatalytic reaction in aqueous 4-chlorophenol (4CP) solution and compared to those of TiO2 anatase with almost the same surface area of approximately 200 m2/g. The characteristics of commercial P-25 TiO2 powders with the surface area of approximately 55 m2/g were also compared to rutile and anatase powders. The rutile phase powders surpassed both anatase and P-25 ones in decomposition rate for 4CP. The excellent photo-oxidative ability of the powder was dependent on the specific powder-preparation method, which led to a direct crystallization in aqueous solution, regardless of the crystalline structures of the powders.
I. INTRODUCTION
The photocatalytic properties of the rutile phase of ultrafine TiO2 powder has not been compared accurately with the anatase powders, because the preparation methods to support the similar physical properties, such as the surface area, shape of particles, and so on, have not been proposed so far. Accordingly, the detailed mechanism of the photocatalytic reaction of the rutile powder, including the reason behind its lower photocatalytic efficiency, has not been explained appropriately yet. The main focus in this research field is explaining the photocatalytic reaction of the anatase alone. On the other hand, although nanostructured ultrafine powder consists of a pure rutile phase obtained by homogeneous precipitation process at low temperatures (HPPLT), it displayed superior photocatalytic properties in recovering Cu and Pb ions with the forms of various metal lumps from the aqueous solution by photoreduction in our previous experiments.1 It could be predicted that the superior photoreductive properties of the HPPLT powder would be ascribed to its chestnut bur shape with acicular primary particles. The acicular-shaped nanocrystalline structure helps in increasing the surface area of primary particles that coagulate radially in all directions, probably supporting more rapid photocatalytic reaction between metal ions and photoexcited electrons. J. Mater. Res., Vol. 18, No. 3, Mar 2003
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Therefore, there is an ample interest in accurately characterizing the fact that the photocatalytic properties of the ultrafine TiO2 powder depend mainly on the preparation method rather than the crystalline phase itself under the conditions of the same surface area and acicular type morphology. In this paper, the photocatalytic properties of the rutile powder by HPPLT were compared with those of the anatase powder from the aqueous TiOCl2 solution and commercial P-25 powder. II. EXPERI
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