Obtenção de Nb2O5 nanoestruturado para adsorção de poluentes em meio aquoso

Abstract

The focus of this work is to synthesise Nb2O5 nanoparticles by peroxide oxidation method, and to apply these particles in the adsorption of the pollutants above mentioned, in aqueous media. The synthesis variables were temperature (100 °C and 150 °C) and time (4, 12 and 24 hours). These nanoparticles were characterized by XRD, Raman, thermal analysis, FTIR, zeta potential and scanning electron microscopy (SEM). The samples presented high surface area, which varied between 126 and 206 m²/g, and orthorhombic crystal structure. By FTIR, it was verified that increase in the synthesis time of the samples obtained at 100 ºC caused a reduction in the amount of adsorbed water, and that in the samples synthesized at 150 °C, the increase in the synthesis time promoted surface hydroxylation. The zeta potential values were below -27 mV, indicating that the nanoparticles are stable in aqueous suspension. Scanning electron microscopy (SEM) analysis revealed that there was no significant variation in nanoparticles morphology. In the adsorption studies, all samples showed a high percentage of adsorption for the Mn2+ ion, ranging from 41.3% to 78.9%. For MB, a sample obtained at 150 °C for 24 was selected, the adsorption assays were promising, showing that the equilibrium time was 90 min and the adsorption rate followed second-order kinetics, suggesting chemical diffusion as the dominant process. The best-fitting isotherm model was Freundlich's. Thus, the material has a high adsorption capacity because it is nanometric, with high surface area, stability in solution and, mainly, due to the hydroxylated groups on its surface.