Influência das propriedades dos compósitos de dióxido de titânio do hexatitanato de sódio na sua atividade fotocatalítica

Abstract

Titania based materials are widely studied with well-known applications for anatase and rutile TiO2 phases. However, brookite, which is more difficult to obtain, has caught the scientific community interest specially at photocatalysis field. Among many synthesis methodologies, hydrothermal method stands out, with different synthesis conditions reported, but only few works have referenced its synthesis by microwave assisted hydrothermal method. Sodium titanates have also been reported and seem to be promising for different applications. Na2Ti6O13, with tunnel-like structure is known as a good photocatalyst. In this sense, the aim of this work is to evaluate different synthesis conditions employing hydrothermal for brookite obtainment. pH, sodium concentration and temperature on the microwave oven were the factors evaluated. Na2Ti6O13 and Na2Ti6O13/rutile composites were obtained with hydrothermal treatment and calcination. Na2Ti6O13 were also obtained by Pechini method for the first time (data in the appendix) All samples obtained were characterized and employed as catalysts for the photodegradation of remazol golden yellow dye (RNL) aqueous solution, the results suggested the main influence of phase composition and short-range disorder on the activity. The materials obtained were considered good photocatalysts, highlighting the sample with 31% of brookite, and Na2Ti6O13 obtained by hydrothermal method, which were able to promote around 80% and 96% of RNL decolorization after 4 h of irradiation, respectively. EPR studies of the calcined materials indicated the presence of Ti3+bulk defects, possibly related to a morphological orientation, for those samples obtained by microwave assisted synthesis; so among titanates and composites, these defects, rutile ratio and short order disorder were shown to play a central role in the photocatalytic activity.