TiO 2 nanoparticles containing sulphonated cobalt phthalocyanine: Preparation, characterization and photocatalytic performance A. Ebrahimian a,b,c, *, M.A. Zanjanchi b, **, H. Noei c , M. Arvand b , Y. Wang c a Faculty of Fouman, College of Engineering, University of Tehran, Fouman 43515-1155, Iran b Department of Chemistry, Faculty of Science, University of Guilan, Rasht 41335, Iran c Laboratory of Industrial Chemistry, Ruhr-University Bochum, D-44780 Bochum, Germany Introduction In recent years, there has been a substantial amount of research and development in the area of photocatalytic degradation and heterogeneous photocatalysis. Heterogeneous photocatalysis is an attractive and highly efficient method for the degradation of toxic and non-biodegradable environmental pollutants commonly present in domestic or industrial wastewater [1–8]. The use of innovative processes based on photocatalytic technologies for the degradation of organic compounds in water is economically advantageous and is environmentally friendly. Photocatalytic reactions on TiO 2 semiconductors are of great interest because of their applicability to the treatment of a large variety of pollutants [9–13]. Due to the width of the band gap of TiO 2 (3.2 eV), the processes of catalytic oxidative destruction are accomplished upon irradiation with light of the UV region, where only approximately 4% of the solar radiation is effective. The anchoring of pigments, especially phthalocyanine complexes (Pcs) on wide- band gap semiconductors is an alternative method to overcome this problem. By this means a dye (sensitizer) adsorbed on TiO 2 surface is excited by absorbing visible light, and an intercompo- nent electron transfer is achieved in the couple molecular semiconductor–TiO 2 [14–17]. Metallophthalocyanines are very stable metal complexes, and a number of properties contribute to their extraordinary versatility. These include their redox activity, high thermal stability and no toxicity. Close position of the TiO 2 conduction band levels with respect to the LUMO orbital energy of the phthalocyanine favours the charge transfer. When a dye molecule absorbs visible light, it is excited to a higher energy state, the excited dye then injects electrons into the conduction band of TiO 2 . The injected electrons are then scavenged by the surface adsorbed oxygen to yield species such as O 2  , HO  , etc. [17]. Our recent inspection showed that few studies have been devoted to the characteristics and application of phthalocyanines in TiO 2 -based photocatalytic systems. A number of reports concern characterization and application of the catalysts Journal of Environmental Chemical Engineering 2 (2014) 484–494 A R T I C L E I N F O Article history: Received 21 November 2013 Accepted 30 January 2014 Keywords: TiO 2 Photocatalyst Cobalt phthalocyanine 2,4-Dichlorophenol Degradation A B S T R A C T In order to utilize visible light more efficiently in the photocatalytic reaction, TiO 2 nanoparticles containing different amounts of sulphonated cobalt phthalocyanine (CoPcS) were synthesized. The prepared photocatalysts were characterized by X-ray diffraction, N 2 physisorption, UV–vis diffuse reflectance spectroscopy, transmission electron microscopy, thermogravimetric analysis, and FTIR. The characterization results show that CoPcS is anchored on the surface of TiO 2 through SO 2 -O-TiO 2 bonds. The photocatalysts were used for the degradation of 2,4-dichlorophenol (2,4-DCP) monitored by UV–vis spectrophotometry. The catalysts revealed enhanced activity for the degradation of 2,4-DCP compared to that of pure TiO 2 , which is attributed to the cooperative function of the two components of the photocatalyst. The photocatalyst containing 2.24 wt% CoPcS exhibited the highest photocatalytic activity for 2,4-DCP degradation, which was completed within 150 min using a 0.2 g/L dose of this photocatalyst in a 40 mg/L solution of the pollutant. The reactions follow zero-order kinetics, and the observed rate constants values change with initial concentrations of 2,4-DCP. The recyclability of the catalyst was tested, it can be used at least five times before the photocatalytic efficiency reaches that of pure TiO 2 and oxalic acid and maleic acid were the major intermediate species at the final stage of the degradation process as identified by gas chromatography-mass spectrometry. ß 2014 Elsevier Ltd. All rights reserved. * Corresponding author at: Faculty of Fouman, College of Engineering, University of Tehran, Fouman 43515-1155, Iran. Tel.: +98 132 7234927; fax: +98 132 7237228. ** Corresponding author at: Department of Chemistry, Faculty of Science, University of Guilan, Rasht 41335, Iran. Tel.: +98 131 3226643; fax: +98 131 3220066. E-mail addresses: aebrahimian@ut.ac.ir (A. Ebrahimian), zanjanchi@guilan.ac.ir (M.A. Zanjanchi). Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jec e 2213-3437/$ – see front matter ß 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jece.2014.01.022