Macro-mesoporous sulfated titanium dioxide from sol-gel associated to emulsion templates for photocatalysis application

Reference Presenter Authors
17-032 Paula Glazielli Paulino Moraes Moraes, P.G.(Instituto de Química/UNESP); Alves-Rosa, M.A.(Instituto de Química/UNESP); Pulcinelli, S.H.(Instituto de Química/UNESP); Santilli, C.V.(Instituto de Química/UNESP); Titanium dioxide has attracted great interest due to the diversity of its properties. This oxide can exhibit anatase and rutile crystalline structures, which consist of Ti octahedra (TiO6) arranged in different ways. The rutile phase is thermodynamically stable at temperatures close to the ambient whereas the anatase turns into rutile at temperatures between 600 and 700 °C. The sulfation of TiO2 is an alternative to stabilize the anatase phase, the more photoactive phase of titania, the surface area upon high-temperature calcination treatment as well as to promote the porous structure. In this study, the proposed process aims to combine the formation of porous titanium dioxide and its sulfation in a single step by sol-gel process combined with emulsion templates; to shape the porous structure surfactants and oil were added under stirring in order to generate a macro-mesoporous structure from emulsion templates, generating photoactive ceramic foams after drying and thermal treatment. According to the structural characterization by XRD the addition of sulfate species leads to a stabilization of anatase phase, since single-phase materials with anatase as only phase were observed even at 700 °C for sulfated materials. However, for non-sulfated TiO2 calcined at 700 °C, the rutile phase was observed as a second phase. FTIR spectra show bands around 1050-1250 cm-1 assigned to links of SO42- groups in the sulfated TiO2 samples. The observed N2 adsorption-desorption isotherms are typical of macro-mesoporous materials. For the non-sulfated TiO2 foam the surface area value (S) is equal to 50.37 m2/g, while for sulfated samples S increases to 62.06 and to 79.96 m2/g as Ti4+:SO42- ratio increases from 0.1 to 1. The photodegradation reaction of methylene blue dye under UV radiation follows a first order mechanism; TiO2 sulfated samples exhibiting higher reaction constant rates than the non-sulfated ones.
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