Immobilization of TiO 2 on perlite granules for photocatalytic degradation of phenol S.N. Hosseini a , S.M. Borghei b , M. Vossoughi b,c, * , N. Taghavinia c,d a Department of Environment, Islamic Azad University, Science and Research branch, Tehran, Iran b Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran c Institute for Nano-science and Nano-technology, Sharif University of Technology, Tehran, Iran. d Department of Physics, Sharif University of Technology, Tehran, Iran Received 13 August 2006; received in revised form 21 December 2006; accepted 23 December 2006 Available online 7 January 2007 Abstract The photocatalytic degradiation of phenol by nanoTiO 2 particles coated on perlite as a new composite nano-catalyst was investigated. Titanium dioxide (Degussa P-25) was immobilized on three different supports (perlite granules, glass plates and steel fiber) by a very simple and inexpensive method. Perlite granules have a porosity of more than 95%, which allows them to stay afloat on water surface. This gives the medium a unique characteristic from the processing point of view, which enables it to get wetted with the polluted solution without requiring any pumping and simultaneously be exposed to the radiation source when coated with the photocatalyst. The photocatalytic activity of prepared catalysts was tested in appropriate batch reactors. HPLC analyses was used for measuring the concentration of components, XRD and SEM analyses was carried out for characterization including anataze-rotile phase ratio, crystal size and morphology of prepared catalysts. The XRD results did not reveal any significant changes in the structure of P-25 as a consequence of the applied immobilization process. Also, well and uniform coating of TiO 2 on supports were confirmed by SEM method. The obtained results of the photocatalytic treatment experiments of water synthetically polluted with phenol showed a fairly good performance for the three immobilized catalysts. The rate of phenol degradation was positively affected by UV light intensity, according to different intensity of UV lamps, the kinetics of photocatalytic reaction follows a pseudo-first- order model. Also control experiments confirmed that the effects of adsorption and degradation of phenol onto the TiO 2 /perlite catalysts in the dark conditions were negligible. # 2007 Elsevier B.V. All rights reserved. Keywords: Photocatalysis; Phenol; Titanium dioxide (TiO 2 ); Perlite; Steel Fiber 1. Introduction Photocatalytic technology has been widely studied since 1970 [1]. Photocatalytic oxidation has also been proposed since 1980 as an effective method for treatment of toxic and polluted water [2]. So far vast amount of energy and effort has already been devoted to this subject by researchers, and now it seems to be the time to find more practical ways to use the technology at industrial scale. The key to the problem of industrializing the technology seems to be immobilization of TiO 2 nano-particles, as the most successful photocatalyst reported [3–6], on solid media suitable for the treatment process without lowering its photocatalytic efficiency. This study is an effort to propose a technique for utilization of nano TiO 2 particles more efficiently and at minimum cost. Many techniques have been developed for immobilizing TiO 2 catalysts onto a solid substrate, for example, dip coating from suspension, spray coating, sputtering, sol–gel-related methods, and electrophoretic deposition. Also, different types of substrates have been tested; for example, glass beads [7], glass tubes [8], fiberglass [9], quartz [10], stainless steel [11], aluminum [12], activated carbon [13], and silica [14]. Stainless steel was employed as the substrate of TiO 2 for the photocatalytic degradation of formaldehyde [11]. The steel www.elsevier.com/locate/apcatb Applied Catalysis B: Environmental 74 (2007) 53–62 * Corresponding author. Tel.: +98 21 66165487. E-mail address: vossoughi@sharif.edu (M. Vossoughi). 0926-3373/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2006.12.015