Applied Catalysis B: Environmental 101 (2011) 461–470 Contents lists available at ScienceDirect Applied Catalysis B: Environmental journal homepage: www.elsevier.com/locate/apcatb The influence of rapid heat treatment in still air on the photocatalytic activity of titania photocatalysts for phenol and monuron degradation Zs. Pap a,b , V. Danciu b , Zs. Cegléd a , Á. Kukovecz c , A. Oszkó d , A. Dombi e , K. Mogyorósi a,∗ a Department of Inorganic and Analytical Chemistry, University of Szeged, P.O. Box 440, Szeged, H-6701, Hungary b Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, Arany János 11, RO-400028 Cluj-Napoca, Romania c Department of Applied and Environmental Chemistry, University of Szeged, Szeged, H-6720 Rerrich B. tér 1, Hungary d University of Szeged, Department of Physical Chemistry and Material Science, Aradi Vt. 1, H-6720 Szeged, Hungary e Institute of Material Science and Engineering, University of Szeged, P.O. Box 440, Szeged, H-6701, Hungary article info Article history: Received 11 August 2010 Received in revised form 12 October 2010 Accepted 14 October 2010 Available online 21 October 2010 Keywords: Titania Anatase Rutile Nanoparticles Phenol Monuron Photocatalysis Sol–gel method Rapid crystallization UV irradiation abstract Titanium dioxide photocatalysts were prepared by a new synthesis method that involves rapid heating with short and medium exposures of the sol–gel prepared amorphous starting materials at different temperatures and calcination times (RHSE and RHME series). Samples were also synthesized using con- ventional calcination methods (applying slow heating and long exposure times, SHLE series). Both sets of samples were characterized by various methods, such as TG-DTA, XRD, SEM, TEM, DRS, FT-IR, TOC and XPS techniques and by sedimentation experiments. The RHSE and RHME samples have good crystallinity and consist of anatase and rutile mixtures. The photocatalytic activity of catalysts was studied in suspen- sions using phenol and monuron as model substrates. The best UV performance was found for the RHME sample prepared at 600 ◦ C with 60 min of exposure. This sample has high UV activity and is comparable to Aeroxide P25 TiO 2 reference photocatalyst for both substrates. The RHSE and RHME samples significantly exceeded the performance of SHLE samples. The loss of surface OH groups during long time calcination was assumed to have a negative effect on the activity of SHLE samples due to a high degree of aggregation of the particles in aqueous solutions. The improved photocatalytic performance is attributed to the higher level of absorption of light in the near-UV range. This new more economic treatment strategy could have major impact on materials engineering of UV and VIS active photocatalysts prepared via sol–gel methods, especially using acetic acid and aqueous solution of ammonia. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In the recent years the number of publications referring to the synthesis of nonmetal doped titania, especially nitrogen doped TiO 2 has significantly increased [1]. There are numerous methods for synthesizing titanium dioxide. The most common method is the sol–gel process but there are other non-conventional synthe- sis routes including ball-milling [2], flame hydrolysis [3] and laser pyrolysis [4]. Sol–gel methods are very popular due to the procedure being relatively straightforward and highly versatile. Many titanium pre- cursors can be used including titanium tetraisopropoxide [5–14]; titanium tetraetoxide [15,16]; titanium tetrabutoxide [17–20] and titanium tetrachloride [21]. Trace amounts of nitrogen can be incor- porated within these systems using numerous different doping precursors including triethylamine [5,18], ammonium chloride [6], ∗ Corresponding author. Tel.: +36 62 544 338; fax: +36 62 420 505. E-mail address: k.mogyorosi@chem.u-szeged.hu (K. Mogyorósi). ammonia [22], ammonium carbonate [7] and urea [17,21]. Research efforts are focusing mostly upon the effective incorporation of dop- ing species during the hydrolysis of titanium precursors. Nitrogen doped samples are usually calcinated at 400–500 ◦ C since higher temperature is disadvantageous for the incorporation of nitrogen in the crystal lattice. The current aim of synthetic research is to prepare visible light sensitive photocatalysts using different doping techniques. How- ever, a synthesis method resulting in high UV and VIS activity at the same time is highly desired. In many instances, the visible light sensitive photocatalysts are not very effective under UV irradiation when compared to highly efficient commercial photocatalysts, such as Aeroxide P25 TiO 2 . Therefore the overall activity of these visible light sensitive photocatalysts under solar irradiation may be lower than a highly efficient near-UV active photocatalyst. The quality of the photocatalysts can be strongly influenced by the sample’s crystal structure. These structures are determined by the precipitation of the amorphous materials and subsequent heat treatment. These steps are key components in all synthesis methods. Titania nanocrystals (doped or undoped) have been syn- 0926-3373/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2010.10.017