Diclofenac degradation by heterogeneous photocatalysis with Fe₃O₄/Ti_xO_y/activated carbon fiber composite synthesized by ultrasound irradiation

In this work, a photocatalytic system to degrade diclofenac was developed using a composite Fe₃O₄/Ti_xO_y on an activated carbon fiber. Diclofenac is widely used as an anti-inflammatory compound worldwide and it is constantly being added as waste in the environment (Heberer 2002 J. Hydrol. 266 175-89), exceeding the permissible maximum concentration in the wastewater (GEO-3 2002 Programa de las Naciones Unidas para el Medio Ambiente; Golet et al 2003 Environ. Sci. Technol. 37 3243-9; Oviedo et al 2010 Environ. Toxicol. Pharmacol. 29 9-43; Le-Minh et al 2010 Water Res. 44 4295-323; Legrini et al 1993 Chem. Rev. 1093 671-98). The composite was synthesized by sol-gel technique with and without ultrasound irradiation (Singh and Nakate 2014 J. Nanopart. 2014 326747). The solids were deposited by ultrasound irradiation on active carbon fiber in order to optimize the diclofenac degradation. The solids were characterized by x-ray diffraction (XRD), nitrogen physisorption (BET), and scanning electron microscopy with EDS microanalysis (SEM-EDS). The crystal size was calculated with the Debye-Scherrer equation, and the band gap values by the diffuse reflectance method. The evaluation process was studied by UV-vis spectroscopy (Rizzoa et al 2009 Water Res. 43 979-88). It was found that in this synthesis method (ultrasound), textural properties such as porosity, specific surface area and morphology depend on the ultrasound irradiation. The proposed system, Fe₃O₄/titanium oxide hydrate showed better degradation profile than TiO₂ anatase phase; the increase of diclofenac degradation was attributed to the textural properties of the composite, it avoids the filtering process since the separation can be achieved by magnetizing and/or decantation.