Avaliação da relação ácido cítrico/cátions metálicos na estrutura e morfologia de nanopós de TiO2 sintetizado pelo método Pechini para uso como fotocatalisador.

Abstract

Materials with potential for application in photocatalysis has been studied since the mid 70's, so know the structure and morphology of these materials is of fundamental importance to obtain new materials or improve the characteristics of existing materials. Thus, this paper proposes to obtain titanium dioxide (TiO2) for application in photocatalysis through the polymeric precursor method, known as the Pechini method,. The influence of the amount of citric acid / metal cations in proportions 2:1, 3:1, 4:1 and 5:1 were investigated to understand its influence on the structural, morphological and photocatalytic performance of TiO2 to remove of organic pollutants. The synthesized samples were characterized by thermal analysis (TGA / DTA), X-ray diffraction (XRD), structure refinement by the Rietveld method, absorption spectroscopy in the region with Fourier transform (FTIR), particle size distribution, textural analysis (BET / BJH), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS) and in photocatalytic test bench using the dye methyl orange. The results of refining the parameters of the crystal structure proves the efficiency of the method in obtaining samples of TiO2 nano-particle size. Increasing the ratio of citric acid and the metal ions used in preparing samples of TiO2, favored the emergence of the second phase rutile, which contributed to the increase in crystallite size and particle size, with a reduction in specific area. The adsorption isotherms showed that all samples have characteristics of mesoporous materials with morphology of clusters formed non-uniform, irregularly shaped, consisting of nanoparticles. What about the photocatalytic performance, it was observed that samples of TiO2 for all ratios between citric acid and metal cation that occurred 100% of discoloration during the 240 minutes of reaction. Highlighting the photocatalytic activity of the sample 2:1 probably due to the formation of pure anatase phase demonstrating the high efficiency of the total bleaching of methyl orange in 90 minutes.