Síntese, caracterização e avaliação das propriedades fotocatalíticas de nanopartículas de Bi2WO6 e Bi2WO6׃ x% Zn+2

Abstract

Nanostructured materials have been widely studied, not only for their new properties and possible technological applications, but also in the search for a better understanding of the physical and chemical aspects caused by their reduced dimensions. The application of new synthesis routes for nanostructured materials has led to materials with peculiar characteristics, which are responsible for the emergence of new properties and applications. In particular, tungstates have aroused great interest in recent decades as they play a fundamental role in emerging technologies for applications in sectors ranging from the environment, through the development of new catalysts, to energy, such as through the development of materials with optical properties for application in solid-state lighting devices. The physicochemical properties of tungstates are closely dependent on the synthesis method used and the morphology obtained by the particles. In this context, this work aims to carry out the synthesis, characterization and evaluation of the photocatalytic properties of bismuth tungstate nanoparticles, both in its simplest form Bi2WO6 and zinc-doped Bi2WO6׃ x% Zn+2 at 1%, 2%, 4% and 8%. The chemical synthesis used in this work was the sonochemical method, at pH 7 for 15 minutes, which proved to be efficient in obtaining nanoparticles. The samples were characterized structurally by the X-ray diffraction technique (XRD) and morphologically by the field emission scanning electron microscopy technique (FEG-SEM). The photocatalytic properties of the samples were investigated from the degradation of methylene blue (MB) and Rhodamine B (RhB) dyes and their quantification was performed by the UV-visible (UV-Vis) spectroscopy technique. The XRD results indicated the formation of the orthorhombic phase of bismuth tungstate, according to JCPDS Card No. 39-256. There was no secondary phase formation, indicating that doping was successful. The UV-Vis analysis showed that with Zn+2 doping there was a shift of the absorption edge towards the red region. Egap values experienced small variations due to the appearance of defects in the network. The FEG-SEM of the samples revealed particles with irregularly shaped, spheroidal and rod-shaped morphologies. Bi2WO6-pure showed the best photocatalytic performance in the two dyes tested due to the higher efficiency of separation of charges generated by irradiation (UV). Bi2WO6-pure degraded 82% of MB and 57% of RhB, and showed a better performance in decreasing the concentration of MB dye when subjected to UV radiation.