Photocatalysis of methylene blue on titanium dioxide nanoparticles synthesized by modified sol-hydrothermal process of T
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Catalysis Letters, Vol. 117, Nos. 3–4, September 2007 (Ó 2007) DOI: 10.1007/s10562-007-9115-8
Photocatalysis of methylene blue on titanium dioxide nanoparticles synthesized by modified sol-hydrothermal process of TiCl4 Sung-Yeon Kim,a,b Tae-Ho Lim,a,b Tae-Sun Chang,a,* and Chae-Ho Shinb a
Advanced Chemical Technology Division, Korea Research Institute of Chemical Technology, Daejeon 350-343, Korea b Department of Chemical Engineering, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea
Received 1 April 2007; accepted 2 April 2007
Titanium dioxide nanoparticles were synthesized by the hydrolysis and condensation of TiCl4, an economic titanium precursor, in a mixed solvent of iso-propyl alcohol and water. As-prepared powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy filtering transmission electron microscopy (EF-TEM). To examine the photocatalytic activity of the as-prepared TiO2, the photodegradation of MB which is a typical dye resistant to biodegradation has been investigated on TiO2 powders in aqueous heterogeneous suspensions. The photocatalytic activity of TiO2 powders prepared by the hydrolysis of TiCl4 in the mixed solutions of iso-PrOH/H2O exceeded that of commercial TiO2 powders. The apparent first order rate constants (kapp) for the photodegradation of methylene blue (MB) showed a good correlation with the absorbance area obtained by UV-VIS DRS on wavelength in the limits of used lamp emission 300420 nm. KEY WORDS: TiO2 nanoparticle; photoactivity; methylene blue; TiCl4.
1. Introduction Nano-sized titanium dioxide (TiO2) is an excellent candidate for a multi-purpose photocatalyst, because of its optical properties, including a high refractive index leading to a hiding power and whiteness, as well as it chemical stability and relatively low production cost [1]. The photocatalytic approach is attractive in what regard catalytic activity. Titanium dioxide powders, added to organic contaminated water and illuminated by mild UV light, works as a photocatalyst, oxidizing dissolved toxic organic compounds into relatively benign species. Whereas organic compounds are not fully decomposed by conventional technology they can be completely decomposed to H2O and CO2 by photocatalysis. In addition, no secondary pollutants are generated in the latter process. When TiO2 absorbs a photon of energy greater than or equal to the band gap energy, an electron moves to a conduction band from a valence band. An electron is distributed in the conduction band and an electron vacancy or ‘‘hole’’ is distributed in the valence band. If charge separation is maintained, the electron and hole may migrate to the catalyst surface where they participate in redox reactions with adsorbed species. A hole and an electron range respectively at the valence band and conduction band by the irradiation of light. A hydoxyl radical (–OH) and superoxide radical then occur *To whom correspondence should be addressed. E-mails:
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