Síntese, caracterização e aplicação de óxidos de ferro na degradação de corante têxtil

Abstract

In view of the intense contamination of water resources, concern about environmental issues is growing. Currently, many of the contaminants that reach water bodies such as pesticides, drugs, dyes, among others, are not efficiently eliminated by conventional methods of treatment. Therefore, there is a need to develop and improve efficient forms of treatment to eliminate this type of recalcitrant compound. A significant portion of the contamination of water resources comes from industrial effluents disposed of incorrectly. Among these, the effluents from the textile sector stand out for the large volume of effluents generated, with a high potential for risk to the aquatic environment and human health. In this context, the present work aims to use advanced oxidative processes for dye degradation. Therefore, maghemite, zinc ferrite and cobalt ferrite doped with copper and nickel were synthesized by hydrothermal route and coprecipitation, using nitrates as metal precursor salts, aiming at application in the degradation of the methylene blue model dye. The materials were characterized by XRD, XRF, SEM-FEG, N2 physisorption isotherms, Molecular Spectroscopy in the UV-Vis region, Diffuse Reflectance Spectroscopy in the UV-Vis region, Molecular Fluorescence Spectroscopy and Zeta potential. The obtained materials had a large surface area, with particles in the nanometric scale quite agglomerated, varying the surface electrical charge according to the pH of the medium. Adsorption tests, H2O2 photolysis, photo-Fenton degradation tests and radical scavengers were performed to better understand the dye removal mechanism. For the degradation tests, aliquots were removed at intervals established for spectrophotometric monitoring. The degradation results showed 99% dye discoloration for the samples of maghemite and ferrites, after 180 minutes of reaction. According to the investigation of the mechanism, the holes and hydroxyl radicals proved to be the main responsible for the degradation of the dye. The materials obtained showed to be very promising, with low leaching of iron ions, using an LED lamp, which makes it much more viable, both the practical use of the catalyst and the economic issue. In addition, the magnetic property exhibited by the synthesized materials enabled the total and efficient separation of the catalyst for reuse in up to four cycles, without loss of photocatalytic activity.