Síntese, caracterização e aplicação de compósitos de polipirrol/TiO2 em processos fotocatalíticos

Abstract

In the last decades, new technologies of waste treatment have been developed, and the heterogeneous photocatalysis stands out among them for transforming the great majority of the contaminants into carbon dioxide, water and inorganic anions, compounds less harmful to the environment. This is a simple process that needs just a semiconductor and a source of radiation. Titanium dioxide is the most widely used semiconductor due to its remarkable physical, chemical and photoelectric properties. However, it has some features that limit its use. Hybrid composites of conducting polymers and inorganic oxides such as polypyrrole and titanium dioxide have been studied to solve these problems. In this work hybrid solids of these components were synthesized by the chemical synthesis of “in situ” polymerization in different molar ratios of titanium dioxide, by different routes and with different types of dispersion of the particles during the synthesis. The composites were characterized by TGA, SEM and diffuse reflectance spectroscopy. In order to test the capacity to remove the methylene blue dye by photocatalysis, experiments were carried out with 30 min of adsorption in the dark, followed by 90 min of irradiation of a 20 W UV lamp. The results showed that the nanocomposites prepared by route 1 (sequential addition of pyrrole, TiO2 and oxidant) were more thermally stable than the pure polypyrrole. It was also possible to observe that nanocomposites of route 2 (sequential addition of TiO2, pyrrole and oxidant) were more efficient in removing the dye present in aqueous solution, indicating that a synergy occured and not only a physical mixture of its precursors.