CoFe₂O₄@TiO₂ system obtained by the modified-Pechini method

Full text: TiO₂ has been the most applied semiconductor for photocatalytic reactions [1]. In order to improve the removal of the photocatalysts from the reaction medium, a combination of this catalyst with magnetic particles has been used [2]. In this work, the modified-Pechini method was used in the preparation of polymeric resin containing titanium, followed by addition of nanoparticulated CoFe₂O₄ into the resin with different mass ratios between CoFe₂O₄ and TiO₂ and subsequent drying. The system was heat treated at different temperatures (400- 700 deg C) and characterized by X-ray diffraction, infrared spectroscopy, UV-vis spectroscopy and surface area measurements (BET) and XPS. The photocatalytic properties of these materials were also evaluated. XRD patterns showed peaks assigned to anatase and/or rutile, depending on the TiO₂ :CoFe₂O₄ ratio. For smaller amounts (10 and 15%) a decrease in the surface area was observed, assigned at occupation of the pores present in the ferrite. All of the samples kept their magnetic properties, with band gap values similar to the ferrite ones (1.4 eV). Samples with less than 90% of TiO₂ had a low photocatalytic activity. Formation of the core@shell was confirmed by XPS for the sample with 90% of the TiO₂ , which showed only Ti⁴⁺ and very small amounts of Fe³⁺ on the surface, without the presence of cobalt. When the sample with 90% in mass of TiO₂ heat treated at 500 deg C was used in the photocatalytic tests, the discoloration values were 32, 54 and 76%, after 4, 8 and 16 h of irradiation, respectively. References: [1] S. Girish Kumar and L. Gomathi Devi, J. Phys. Chem. A, 115, 13211–13241, 2011. [2] Hua Li, Xianzhe Shi, et. al., J. Chromatogr. A, 1275, 9 – 16, 2013. (author)