Estudo comparativo entre BiFeO3 e Bi2Fe4O9 no processo de fotocatálise heterogênea

Abstract

In this work, the BiFeO3 and Bi2Fe4O9 materials were synthesized by the solid-state and Pechini reaction methods, and afterwards the material showed the best photocatalytic activity. For the synthesis of BiFeO3 in both routes, the powders were calcined at 700 ° C for 10 hours and synthesized at 750 ° C for 10 h. For Bi2Fe4O9, which was also synthesized by both syntheses, with a difference in stoichiometry and calcination temperature (800 ° C - 12 h) and sintering 850 ° C - 10h). The characterization of the samples was obtained by X-Ray Diffraction, X-Ray Spectroscopy by Dispersive Energy coupled to Scanning Electron Microscopy by Field Emission, Spectroscopy in the Ultraviolet-Visible Region, Diffuse Reflectance Spectroscopy, N2 Physiosorption and Analysis of Zeta Potential. The degradation tests took place in a bench reactor, where the pellets were submerged in 250 mL solutions of the tartrazine dye, triclosan and triclocarban with conditions optimized by an experimental design 22. Phytotoxicity and ecotoxicity tests were also carried out on the solutions before and after treatments photochemicals, in addition to adsorption of the contaminant molecules in the pellets and reuse tests of the materials. With the results obtained in the characterization, it was found that BiFeO3 and Bi2Fe4O9, synthesized by the two syntheses, showed significant differences in terms of morphology, surface area, bandgap energy and surface charge. As for the photocatalytic activities, the two materials obtained by both syntheses, presented considerable degradation rates for the three contaminants, however, Bi2Fe4O9 synthesized by the Pechini method was the one that presented the best data: 99% tartrazine degradation, 91% of triclosan and 99% of triclocarban. For all the adsorption tests it was noticed that there is a non-significant adsorption, however necessary for the photocatalytic process to occur. Regarding the reuse of the pellets, it was proven that Bi2Fe4O9 remains stable and efficient in the face of 10 tests. For the ecotoxicity tests performed, there was a reduction in toxicity when compared to solutions without any type of treatment, however the solutions that had Bi2Fe4O9 as a semiconductor during photocatalysis, showed the best results. It is concluded, then, that the Bi2Fe4O9 material synthesized by the Pechini method was the best photocatalyst, proving to be efficient for a future industrial application.