Processo de obtenção, caracterização e aplicação em fotocatálise heterogênea dos compósitos MgO-CeO2 e ZnO-CeO2

Abstract

In the present study, MgO-CeO2 and ZnO-CeO2 composites were obtained by thermal decomposition of the chelates of the Ce, Mg and Zn metals with the 8-hydroxyquinoline chelator, characterized and tested as catalysts in the degradation of BF-4B Red Reactive dye by heterogeneous photocatalysis process. The metal complexes with the 8-hydroxyquinoline chelator were obtained by a synthetic coprecipitation route in aqueous medium by raising the pH. FTIR analysis of the synthesized mixed complexes proved to obtain the complexes by observing the characteristic bands that showed the binding of the chelant to the metals. Simultaneous thermal analysis (TGA-DTG-DTA) of the complexes made it possible to trace and characterize the thermal behavior profile of the complexes under the conditions to which they were subjected, as well as to identify the thermal decomposition events of the complexes and the temperatures of obtaining the desired composites. XRD results showed semi-crystallinity characteristics of the complexes, and enabled the identification of the phases of the composites obtained, as well as the proof of obtaining them. SEM images of the composites showed that the obtained composites particles presented characteristics of agglomeration, polycrystallinity and variation of particle size for all the samples, where it was also possible to observe that the particles of the MgO-CeO2 composite were in the form of hollow rods and square basis, which best defined their shape with the increase of the final heat treatment temperature used, and for the ZnO-CeO2 composite, morphology of deformed particles together with particles in the shape of smooth and irregular plates of various sizes. DRS results allowed to obtain the band gap values of the composites, whose values increased with the increasing in the thermal treatment temperature. Results of the tests applying the materials as catalysts in the degradation process of the BF-4B Reactive Red dye by heterogeneous photocatalysis indicated that the materials are not suitable, since their presence in the process has a retarding effect on the degradation of the dye tested. These effects on the catalytic tests may be associated with the low affinity between the composites and the BF-4B Red Reactive dye, shown by the dye adsorption tests by the composites, under the conditions used for the tests.