Degradação da cafeína via fotocatálise por diferentes fotocatalisadores

Abstract

The concern about the environment has been growing over the years, especially with respect to the maintenance of forests and water resources. Along with the improvement of technologies, it is easier to identify and quantify compounds in water supply. The recently identified compounds are called emergent pollutants, for they do not fit any environmental legislation and its effects to the human health are not known. Among them, it is highlighted the pharmaceutical products, organic compounds and hormones. In order to guarantee the quality of the water supply, it is studied methods of removing and degrading these compounds, which are not degraded in conventional treatment systems. In this scenario, the objective of this paper was to search in the photocatalytic process, a semiconductor capable of effectively degrading molecules of caffeine in water samples. In this study, it was used three different semiconductors (TiO2, Nb2O5 e ZnO). The tests of capacity of degradation were conducted in a batch reactor, using artificial radiation and control of temperature. Besides the tests with suspended catalysts, the semiconductors were immobilized in alginate spheres, in order to favor the process of removing these semiconductors from the water, once when it is suspended, the removal of these semiconductors would add another process to the water treatment. Either the TiO2 or the Nb2O5 were not efficient in degrading the molecules of caffeine, whereas the zinc oxide was capable of degrading up to 90% of the pollutant in less than 120 minutes. It was also evaluated the effect of temperature of calcination of the semiconductor on the degradation of caffeine, claiming that the zinc oxide is more efficient when calcined at 400oC. On the other hand, when immobilized in alginate spheres, the amount of caffeine degraded by ZnO was close to zero, making the use of the methodology of immobilization not feasible for the desired application.