Catalisadores de Ag/Nb2O5 imobilizados: uma alternativa para a degradação do 17α-etinilestradiol em processo contínuo

Abstract

This study describes the application of Nb2O5 and Nb2O5 catalysts promoted with Ag, in suspension and immobilized in alginate spheres, for the degradation of 17α-ethinylestradiol (EE2). The techniques used for the characterization of photocatalysts consisted of: X ray diffraction, surface specific area (B.E.T.), volume and pore diameter, photoacoustic spectroscopy, scanning electron microscopy with coupled dispersive energy spectroscopy (SEM/EDS) and Point of zero charge (PZC). The catalysts were synthesized at different calcination temperatures and with different silver metallic charges. Among the operating conditions analyzed are the pH, concentration of the catalyst and the source of radiation emission. The results indicated that the catalyst that showed the greatest catalytic activity in EE2 degradation, was the catalyst with 5% silver impregnated (5%Ag/Nb2O5) calcined at 700°C, promoting a removal of 97.8% of the initial concentration of the pollutant in the 120 minutes of reaction. The design of experiments indicated that the nominal silver load is a statistically significant factor, within the 95% confidence interval. The increase in the nominal silver charge leads to an increase in catalytic activity, further degrading the contaminant. The immobilization of the catalyst in alginate spheres implied a reduction in the degradation, being able to remove 69.2% of the initial EE2, in a batch system. In the continuous system, the immobilized catalyst degraded a total of 37.3% of EE2, with a flow rate of 10 L.h-1 . The reuse of the catalyst proved to be promising, but it represented a drop in removal, degrading a total of 27% of the initial concentration of EE2 in the third cycle of use