Colloids and Surfaces A: Physicochem. Eng. Aspects 367 (2010) 140–147 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journal homepage: www.elsevier.com/locate/colsurfa Sulfated Fe 2 O 3 –TiO 2 synthesized from ilmenite ore: A visible light active photocatalyst York R. Smith a,b , K. Joseph Antony Raj a , Vaidyanathan (Ravi) Subramanian b , B. Viswanathan a,∗ a Department of Chemistry, National Centre for Catalysis Research, Indian Institute of Technology-Madras, Chennai 600036, India b Chemical & Materials Engineering Department, University of Nevada, Reno 89557, USA article info Article history: Received 16 March 2010 Received in revised form 2 June 2010 Accepted 2 July 2010 Available online 13 July 2010 Keywords: Ilmenite ore Sulfated Fe2O3–TiO2 Photocatalytic activity Phenol oxidation abstract Sulfated Fe 2 O 3 –TiO 2 (SFT) was synthesized by treatment of ilmenite ore with sulfuric acid. The pres- ence of sulfated Fe 2 O 3 –TiO 2 and mixed phases of Fe 2 O 3 –TiO 2 was confirmed by DRIFT spectra and XRD. The dispersion of sulfate displayed thermal stability up to 500 ◦ C. The adsorption–desorption of pyridine investigated by DRIFT spectra revealed the presence of both Brønsted and Lewis acid sites for the samples calcined up to 500 ◦ C. The DRS/UV–vis spectra showed UV and visible light absorbance for samples cal- cined up to 900 ◦ C. A band gap value of 2.73 eV is obtained for 500 ◦ C calcined sample. The photocatalytic activity was evaluated by the oxidation of 4-chlorophenol (4-CP) in aqueous medium under UV–vis and visible light irradiation. SFT calcined at 500 ◦ C demonstrated the highest photocatalytic activity. When compared with high surface area sulfated titania (275 m 2 /g), the photocatalytic activity was greater due to the presence of iron, despite the low surface area of the SFT samples (12–17 m 2 /g). © 2010 Elsevier B.V. All rights reserved. 1. Introduction An increasing awareness of the environmental impacts from pollution and stringent standards on emission regulations has prompted the development of catalytic routes for waste manage- ment. The development and practical application of systems that are clean and green have shown to be a formidable challenge for scientists and engineers. Photocatalytic technologies have shown practical application in antibacterial and deodorant filters for air purification owing to its property of promoting various chemical reactions such as the degradation of aqueous organic pollutants and sources of offensive odors using light. Titania-based mate- rials have received considerable attention for their potential in environmental catalytic applications such as air purification, water disinfection, hazardous wastewater remediation, and deodoriza- tion [1–6]. Recently, the application of titania with different architectures such as nanotubes has been examined [7–9]. Owing to its large band gap (E g = 3.2 eV) titania, however, can only uti- lize photons in the UV region (<380 nm), which limits its practical application for sun light irradiation [7,8,10–13]. One of the promis- ing approaches to overcome this disadvantage is coupling titania with other narrow band gap semiconductors capable of promot- ing charge separation in the visible light spectrum [14,15]. Many studies have reported sensitizer-loaded titania, such as CdS/TiO 2 ∗ Corresponding author. Tel.: +91 44 22574241; fax: +91 44 22574202. E-mail address: bvnathan@iitm.ac.in (B. Viswanathan). [16,17]. CdSe/TiO 2 [18,19], Bi 2 O 3 /SrTiO 3 [20], Bi 2 S 3 /TiO 2 [17,21], ZnMn 2 O 4 /TiO 2 [22], TiO 2 /Ti 2 O 3 [23] under visible light irradiation and have shown efficient visible light photoactivity. In most of these catalysts, the addition of sensitizers reduces the band gap of the material enabling the coupled material to absorb visible light. The conduction band (CB) of the loaded sensitizer has a more nega- tive reduction potential than that of titania enabling visible light photoinduced electrons to be injected into the lower-energy CB of titania. However, the photogenerated holes of the sensitizer remain in the valence band (VB) resulting in an accumulation of holes on the sensitizer leading to photocorrosion of the catalyst. As a result, the stability of the composite photocatalyst becomes less [24]. Furthermore, most currently produced sensitizers are heavy metal chalcogenides (e.g., CdSe, PbS). These may constitute harm to ecological systems and humans as well due to their nanoscale and toxic metal release. A recent study by King-Heiden and coworkers [25] examined the toxicological effects of CdSe/ZnS nanoparticles on the growth of zebrafish embryos and showed Cd toxicity even at very low levels of CdSe nanoparticles. To counter the potential negative environmental problems of using heavy metal sensitizers, iron as a dopant in titania-based sys- tems has been investigated to enhance the photocatalytic efficiency under visible light irradiation [26–30]. Iron is one of the most abun- dant elements found in the Earth’s crust. Similar to titania, iron and its oxides show promise as an eco-friendly catalyst in many applica- tions. For example, FeTiO 3 has a band gap of 2.58–2.9 eV, [31–34] and has been used as a chemical and as a photocatalyst. [32,33] Ye et al. observed that under UV irradiation of TiO 2 –Fe 3 O 4 mixed 0927-7757/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2010.07.001