Avaliação da atividade fotocatalítica de nanopartículas de TiO2 sintetizadas via método sol-gel utilizando acetona como co-solvente

Abstract

In the present work, titanium dioxide (TiO2) nanoparticles were synthesized by sol-gel process using 50% of acetone as a co-solvent to control the hydrolysis of the titanium precursor and as a result, the photocatalytic activity. The intention is to develop and semiconductive oxide with the photocatalytic activity improved for application on photocatalytic process and also with a smaller size of the particle if compared with other materials synthesized by similar process. For the study of structural and electronic changes, different characterization techniques were applied, including X-ray diffraction (XRD) and spectroscopy by UV-Vis diffuse reflectance. X-ray diffraction revealed a crystalline catalyst with the coexistence of the anatase and broquita phases, with anatase being the predominant phase. The size of the crystallite was calculated from the Scherrer equation. The new condition of synthesis does not alter the band gap energy of oxide in relation to that observed for commercial TiO2. After the characterizations, the photocatalytic potential of oxide was evaluated by photodegradation of the nitrogen Ponceau 4R (P4R). It was observed that the discoloration kinetics for the synthesized catalyst occurs in two stages, to a kinetic constant of kdes = 35 x 103 min-1 in the first stage, and kdes = 94 x 103 min-1 in the second stage. Mineralization reached 85% in 120 minutes of reaction under UV irradiation while discoloration was 100%. The apparent kinetic constants of mineralization were kmin = 6,5 x 103 min-1 for the first phase and kmin = 18 x 103 min-1 for the second phase.