Journal of Hazardous Materials 144 (2007) 140–146 Photocatalytic performance of Sn-doped TiO 2 nanostructured mono and double layer thin films for Malachite Green dye degradation under UV and vis-lights F. Sayılkan a , M. Asilt ¨ urk b , P. Tatar c , N. Kiraz c , E. Arpac ¸ c , H. Sayılkan a,∗ a Inonu University, Faculty of Education, Department of Science, 44280 Malatya, Turkey b Inonu University, Faculty of Arts and Science, Department of Chemistry, 44280 Malatya, Turkey c Akdeniz University, Faculty of Arts and Science, Department of Chemistry, 07100 Antalya, Turkey Received 21 July 2006; received in revised form 4 October 2006; accepted 4 October 2006 Available online 12 October 2006 Abstract Nanostructure Sn 4+ -doped TiO 2 based mono and double layer thin films, contain 50% solid ratio of TiO 2 in coating have been prepared on glass surfaces by spin-coating technique. Their photocatalytic performances were tested for degradation of Malachite Green dye in solution under UV and vis irradiation. Sn 4+ -doped nano-TiO 2 particle a doping ratio of about 5[Sn 4+ /Ti(OBu n ) 4 ; mol/mol%] has been synthesized by hydrotermal process at 225 ◦ C. The structure, surface and optical properties of the thin films and/or the particles have been investigated by XRD, BET and UV/vis/NIR techniques. The results showed that the double layer coated glass surfaces have a very high photocatalytic performance than the other one under UV and vis lights. The results also proved that the hydrothermally synthesized nano-TiO 2 particles are fully anatase crystalline form and are easily dispersed in water. The results also reveal that the coated surfaces have hydrophilic property. © 2006 Elsevier B.V. All rights reserved. Keywords: Nano-TiO 2 ; Sn-doping; Thin film; Photocatalysis; Hydrothermal process 1. Introduction Textile industry wastewater is heavily charged with uncon- sumed dyes, surfactants and sometimes traces of metals. These effluents cause a lot of damage to the environment. In most countries researchers are looking for appropriate treatments in order to remove pollutants, impurities and to obtain the decolour- ization of dyehouse effluents [1–3]. Usually, the conventional biological treatment processes do not readily remove dyes from textile wastewater, because of their resistance to biological degradation [4,5]. Various chemical, physical and biological processes are currently used such as flocculation, ultrafiltration, adsorption, ozonation and chlorination [6]. These processes are not efficient because they appear in solid wastes, thus creat- ing other environmental problems requiring further treatment. Therefore, it is necessary to find an effective method of wastew- ater treatment in order to remove hazardous dyes and organics ∗ Corresponding author. Fax: +90 422 341 0042. E-mail address: hsayilkan@inonu.edu.tr (H. Sayılkan). from industry effluents [4]. One of the effective methods of wastewater treatment containing dyes is their photocatalytic degradation in solutions illuminated with UV irradiation, which contains a suitable photocatalyst, mainly TiO 2 sold commer- cially as Degussa P25 and Hombicat UV100. These are recog- nized as excellent photocatalysts and have good prospects in water and air purification [7–9]. The photodegradation of the hazardous materials in colloidal and particulate TiO 2 catalyst suspensions has been well studied [10,11]. However, this appli- cation has not been successfully commercialized, in part because of the costs and difficulties in separating the TiO 2 nanopar- ticles from the suspension after degradation has occured. To solve this problem, TiO 2 film photocatalysts have been widely researched in photodegradation [12–14]. In recent years, nano- TiO 2 based thin films with super-hydrophilic and photocatalytic characteristics have attracted a great deal of attention. They have many advanced functions and features, including self-cleaning, antifogging, deodorizing and sterilizing. When exposed to UV light, organic compounds can be break down with TiO 2 films and enable water to spread evenly on their super hydrophilic surface to easily realize surface self-cleaning. Many researchers 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.10.011