PHOTODEGRADATION OF METHYL ORANGE DYE USING TITANIUM AND TUNGSTEN OXIDES FIBERS AS SEMICONDUCTORS

ABSTRACT

Photodegradation is a good economical alternative for removing organic pollutants from water, and several semiconductor metal oxides have been used in the photodegradation of organic compounds. The use of TiO₂, as a semiconductor most commonly used in heterogeneous photocatalysis, is relevant, due to its efficiency in the decomposition of pollutants from water, air, toxic organic compounds, bacteria, etc. However, the photocatalytic capabilities of TiO₂ are active only in 3% of the solar spectrum, a fact that limits its greater use. Based on this, this work proposes to synthesize TiO₂, and TiO₂ fibers doped with H₂WO₄, by electrospinning, relating the optical and photocatalytic properties of these elements. The X-ray diffraction technique (XRD) was used to determine the phases present. The morphology was observed through scanning electron microscopy (SEM). And photodegradation tests over time, by analyzing the discoloration of 125 mL of a 20 ppm solution of the orange methyl dye, in the presence of the synthesized fibers, when irradiated by UVA-visible light. The results show that the fibers containing tungsten were more efficient in the photodegradation of the methyl orange dye, indicating a greater photoactivity of this material in comparison with the standard P25 catalyst. This is possibly due to the existing synchronization between the chemical and physical properties of titanium and tungsten oxides, and the position of the valence band and the conduction band of WO₃ in relation to TiO₂, which inhibits the recombination of the electron pair/gap allowing the transfer of charges between the two semiconductors, increasing the efficiency of the process.