Nguyen et al. Int. J. Res. Chem. Environ. Vol. 5 Issue 2 (1-8) April 2015 1 ISSN 2248-9649 International Journal of Research in Chemistry and Environment Available online at: www.ijrce.org Research Paper Fabrication and Photocatalytic Activity of Ag/TiO 2 Powder Immobilized TiO 2 Thin Film in Methyl Orange Mineralization * Trang T.T. Nguyen 1 , Vinh Q. Tran 2 , Khanh H. Nguyen 1 , Tan M. Nguyen 3 , Nam T.H. Le 2 1 Department of Environmental Enhancement Solutions, Institute of Environmental Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, VIETNAM 2 Department of Green Chemistry, Institute of Chemistry, 18 Hoang Quoc Viet, Cau Giay, Hanoi, VIETNAM 3 School of Chemical Engineering, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi, VIETNAM (Received 22 nd January 2015, Accepted 08 th March 2015) Abstract: TiO 2 thin film and Ag/TiO 2 powder immobilized TiO 2 thin film were synthesized by dip-coating technique on glass substrate. Fabricated thin films were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Photocatalytic activities of the films were evaluated by the decomposition reaction of methyl orange under UV radiation according to the first-order rate constant k. The experimental results indicated that the initial concentration of the dye solution influenced the decolourization of azo dye methyl orange and the addition of catalyst powder into the TiO 2 sol improved the efficiency of the photocatalytic process of pure TiO 2 thin film. The mineralization of methyl orange was confirmed by chemical oxygen demand (COD) and total organic carbon (TOC) measurements. Keywords: Ag/TiO 2 catalyst, methyl orange, mineralization, thin film, UV irradiation. © 2015 IJRCE. All rights reserved Introduction Textile industry wastewater with high pollutant concentrations contains many chromophore organic compounds which possess durable, difficult biodegradable structure and is highly toxic to humans and animals. If the contamination sources are not handled, they will cause serious environmental pollution, destruction of aquatic ecosystems and destroy the self-cleaning ability of the receiving water body. Some dyes with cyclic structures containing azo groups are cancer-causing agents [1,2] . In recent years, TiO 2 semiconductor photocatalysis has been applied to important issues such as environmental decontamination of water and air [3-5] . When particles of TiO 2 semiconductor are illuminated by UV radiation with energies greater than the band-gap energy of the semiconductor, they will produce electron-hole (e - /h + ) pairs. These e - /h + pairs can move to the surface of the TiO 2 particles to initiate the redox reactions of organic compounds adsorbed on TiO 2 surface. In most cases, this redox process leads to complete mineralization of organic matter to CO 2 and H 2 O [6-8] . Some techniques of metal ion and non-metal ion doping are employed to alter electronic structure and optical properties of TiO 2 in order to extend photoresponse of TiO 2 into the visible light region and slow down the recombination rate of photo-generated e - /h + pairs. The metal ions often used for doping process are Fe, Zn, V, Cr, Cu, Co, Pt, Au, Ag, etc [9-11] . The oxidation method using nano TiO 2 photochemical catalyst revealed many advantages in the field of textile industry wastewater treatment because of the complete destruction and elimination of organic contaminants in the environment [12,13] . The use of TiO 2 photocatalytic powder has some disadvantages that the particles are aggregated at high concentration, the catalysts must be separated from the treated water and reuse of catalyst is complex [14,15] . The manufacture and use of catalyst film will overcome the above drawbacks thus increasing the applicability of