This report investigated the photocatalytic degradation of 2-chlorophenol using TiO2 nanofibers and Ag-doped TiO2 nanofibers, synthesized using the sol-gel and electrospinning techniques, and an ultraviolet light-emitting diode (UV-LED) system as a UV light source. The crystallite size of the Ag-doped TiO2 nanofibers was smaller than that of the TiO2 nanofibers, because silver retrained phase transformation not only controls the phase transformation but also inhibits the growth of anatase crystallites. The activation energies for the grain growth of the TiO2 nanofibers and the Ag-doped TiO2 nanofibers were estimated to be 20.84 and 27.01？kJ/mol, respectively. The photocatalytic degradation rate followed a pseudo-first-order equation. The rate constants ( ) of the TiO2 nanofibers and the Ag-doped TiO2 nanofibers were 0.056 and 0.144？min？1, respectively. 1. Introduction TiO2 is the most widely used photocatalyst owing to its photostability, nontoxicity, low cost, and insolubility in water under most environmental conditions [1]. Excitation of TiO2 generates highly reactive electron-hole pairs that subsequently produce highly potent radicals (such as ？OH and O2？？) that oxidize organic and inorganic pollutants. However, the optimal design of the reactor and the various operational conditions are major concerns in the development and potential applications of photocatalytic processes. Virtually all previous work on photocatalytic degradation with respect to the removal of pollutants from wastewater has been carried out using broad spectral radiation sources, such as UV lamps, and TiO2 as the photocatalyst. The traditional UV source is a mercury vapor high-pressure lamp, which is also a source of gas discharge [2, 3]. The mercury used in this UV lamp is specified as a hazardous air pollutant by the U.S. Environmental Protection Agency and can damage the brain and kidneys. Ultraviolet light-emitting diodes (UV-LEDs) are a new, safer, and energy efficient alternative to traditional gas discharge sources. LEDs are a directional light source, in which the maximum emitted power is in the direction perpendicular to the emitting surface. A typical lifetime of 100,000？h is another advantage of UV-LEDs, whereas the lifetime of gas discharge sources is approximately 1000？h. The electrospinning technique has been recognized as a versatile and effective method for the preparation of nanofibers with small diameters and high surface-to-volume ratios [4–7], and the fabrication of TiO2 nanofibers by electrospinning was first reported in 2003 [8]. Some researchers have
References
[1]
D. Li and Y. Xia, “Fabrication of titania nanofibers by electrospinning,” Nano Letters, vol. 3, no. 4, pp. 555–560, 2003.
[2]
P. Viswanathamurthi, N. Bhattarai, C. K. Kim, H. Y. Kim, and D. R. Lee, “Ruthenium doped fibers by electrospinning,” Inorganic Chemistry Communications, vol. 7, no. 5, pp. 679–682, 2004.
[3]
Y. Xiaodan, W. Qingyin, J. Shicheng, and G. Yihang, “Nanoscale ZnS/ composites: preparation, characterization, and visible-light photocatalytic activity,” Materials Characterization, vol. 57, no. 4-5, pp. 333–341, 2006.
[4]
X. Zhang, S. Xu, and G. Han, “Fabrication and photocatalytic activity of nanofiber membrane,” Materials Letters, vol. 63, no. 21, pp. 1761–1763, 2009.
[5]
S. Madhugiri, B. Sun, P. G. Smirniotis, J. P. Ferraris, and K. J. Balkus Jr., “Electrospun mesoporous titanium dioxide fibers,” Microporous and Mesoporous Materials, vol. 69, no. 1-2, pp. 77–83, 2004.
[6]
B. Xin, L. Jing, Z. Ren, B. Wang, and H. Fu, “Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of ,” Journal of Physical Chemistry B, vol. 109, no. 7, pp. 2805–2809, 2005.
[7]
J. Y. Park, I. H. Lee, and G. N. Bea, “Optimization of the electrospinning conditions for preparation of nanofibers from polyvinylacetate (PVAc) in ethanol solvent,” Journal of Industrial and Engineering Chemistry, vol. 14, no. 6, pp. 707–713, 2008.
[8]
J.-Y. Park and I.-H. Lee, “Characterization and morphology of prepared titanium dioxide nanofibers by electrospinning,” Journal of Nanoscience and Nanotechnology, vol. 10, no. 5, pp. 3402–3405, 2010.
[9]
S. Ramakrishna, K. Fujihara, W. E. Teo, T. C. Lim, and M. Zuwe M, An Introduction Electrospinning and Nanofibers, World Scientific Publishing Company, Singapore, 2005.
[10]
B. Ding, H. Y. Kim, C. K. Kim, M. S. Khil, and S. J. Park, “Morphology and crystalline phase study of electrospun - nanofibres,” Nanotechnology, vol. 14, no. 5, pp. 532–537, 2003.
[11]
C. Pan, L. Dong, and Z.-Z. Gu, “Surface functionalization of electrospun nanofibers by Au sputter coating for photocatalytic applications,” International Journal of Applied Ceramic Technology, vol. 7, no. 6, pp. 895–901, 2010.
[12]
E. T. Bender, P. Katta, G. G. Chase, and R. D. Ramsier, “Spectroscopic investigation of the composition of electrospun titania nanofibers,” Surface and Interface Analysis, vol. 38, no. 9, pp. 1252–1256, 2006.
[13]
A. K. Alves, F. A. Berutti, F. J. Clemens, T. Graule, and C. P. Bergmann, “Photocatalytic activity of titania fibers obtained by electrospinning,” Materials Research Bulletin, vol. 44, no. 2, pp. 312–317, 2009.
[14]
B. Ding, C. K. Kim, H. Y. Kim, M. K. Seo, and S. J. Park, “Titanium dioxide nanofibers prepared by using electrospinning method,” Fibers and Polymers, vol. 5, no. 2, pp. 105–109, 2004.
[15]
B. Xin, L. Jing, Z. Ren, B. Wang, and H. Fu, “Effects of simultaneously doped and deposited Ag on the photocatalytic activity and surface states of ,” Journal of Physical Chemistry B, vol. 109, no. 7, pp. 2805–2809, 2005.
[16]
J. C. Yang, Y. C. Kim, Y. G. Shul, C. H. Shin, and T. K. Lee, “Characterization of photoreduced Pt/ and decomposition of dichloroacetic acid over photoreduced Pt/ catalysts,” Applied Surface Science, vol. 121-122, pp. 525–529, 1997.
[17]
C.-C. Chang, J.-Y. Chen, T.-L. Hsu, C.-K. Lin, and C.-C. Chan, “Photocatalytic properties of porous /Ag thin films,” Thin Solid Films, vol. 516, no. 8, pp. 1743–1747, 2008.
[18]
J. C. Colmenares, M. A. Aramendía, A. Marinas, J. M. Marinas, and F. J. Urbano, “Synthesis, characterization and photocatalytic activity of different metal-doped titania systems,” Applied Catalysis A, vol. 306, pp. 120–127, 2006.
[19]
J. M. G. Amores, V. S. Escribano, and G. Busca, “Anatase crystal growth and phase transformation to rutile in high-area , - and other -supported oxide catalytic systems,” Journal of Materials Chemistry, vol. 5, no. 8, pp. 1245–1249, 1995.
[20]
J. M. G. Amores, V. S. Escribano, G. Busca, and V. Lorenzelli, “Solid-state and surface chemistry of CuO– (anatase) powders,” Journal of Materials Chemistry, vol. 4, no. 6, pp. 965–971, 1994.
[21]
H. E. Chao, Y. U. Yun, H. U. Xingfang, and A. Larbot, “Effect of silver doping on the phase transformation and grain growth of sol-gel titania powder,” Journal of the European Ceramic Society, vol. 23, no. 9, pp. 1457–1464, 2003.
[22]
B. D. Cullity and S. R. Stock, Elements of X-Ray Diffraction, Prentice Hall, Upper Saddle River, NJ, USA, 3rd edition, 2001.
