Síntese e caracterização de ferritas associadas a heteroestruturas de BiVO4 E ZnO para degradação de poluentes via fotocatálise heterogênea

Abstract

Contamination of water resources from effluents generated by anthropic activities drives the development of new technologies for water treatment. Degradation methods of organic pollutant molecules from reactions catalyzed by innovative semiconductor ceramic materials have proven to be an efficient, economically viable, and environmentally sustainable alternative. In this paper, nanoparticles of ferrites from Co (CoFe2O4), Zn (ZnFe2O4) and Bi (Bi25FeO40), bismuth vanadate (BiVO4), zinc oxide (ZnO), and associations between these semiconductors were synthesized by coprecipitation (CP) and coprecipitation followed by microwave-assisted hydrothermal treatment (CPMAHT) at 130°C/30 min. The photocatalytic potential of these materials was evaluated in dye degradation reactions: methylene blue (MB), rhodamine B (RB), and yellow tartrazine (YT). The samples of this study were also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray energy dispersion spectroscopy (EDX), infrared spectroscopy (FTIR) and Raman spectroscopy. The results of the structural and morphological characterization analyzes were used to verify the effect of microwave irradiation, after the coprecipitation process, on the occurrence of microstructural and morphological changes relevant to the photoactivated catalytic property of these materials. From the evaluated results, it was observed that the hydrothermal processing with microwave energy promoted changes in the size of the crystallites, in the morphology, and in the formation of the phases. However, samples of CoFe2O4, ZnFe2O4, ZnO, and structures arising from the association between these oxides did not undergo significant structural changes after hydrothermal treatment. The samples of BiVO4 and of materials from reactions containing bismuth and iron atoms showed dependence on temperature in the formation of single-phase structures with high crystallinity. Mixtures of tz and ms phases of BiVO4 and Bi25FeO40 were identified after CP, originating a monophasic silenite-like structure with a high degree of crystallinity after hydrothermal treatment. With the application of these materials in heterogeneous photocatalysis, it was possible to correlate the photocatalytic efficiency with the type of structure presented. From the association between CoFe2O4 and ZnO, it was observed the formation of a heterostructure stood out in relation to its photocatalytic potential when applied to the degradation reactions of MB, RB, and YT dyes. The heterojunction CoFe2O4/ZnO synthesized via CP, without subsequent thermal treatment, when used in heterogeneous photocatalysis, stood out in relation to the other materials, presenting degradation efficiency of 91.03% for MB, 76.80% for RB, and 75 .57% for YT, in 120 min, with a magnetic response similar to that of pure CoFe2O4. Thus, from this study, a magnetically recoverable heterostructure was obtained in a simple and fast way, with a good response to white light, efficiently achieving the objective of rapid purification of water contaminated with cationic (MB, RB) and anionic (YT) dyes.