Desenvolvimento de fotocatalisadores de silício-cério e silício-titânio para a aplicação na fotodegradação do corante rodamina B

Abstract

The objective of this work was to develop mesoporous nanospheres composed of SiliconCerium and Silicon-Titanium through the soft-template method for later application in the photodegradation of Rhodamine B. The synthesis methodology of the photocatalysts basically consisted of using CTAB micelles as a template soft, and sources of silicon, cerium and titanium for the composition of the inorganic structure in the formation of materials. The syntheses were performed using different Si/Ce and Si/Ti ratios in order to evaluate the influence of the amount of metals in obtaining the nanospheres. The photocatalytic tests were carried out using a Rhodamine B solution exposed to a mercury vapor lamp (125w), using 50 mg of catalyst for each reaction in a total reaction time of 180 min. Aliquots were collected throughout the reaction time to be later analyzed in a UV-vis spectrophotometer. The obtained materials were evaluated in structural, textural and morphological character, through the techniques of DRX, FRX, EDS, Adsorption and Desorption of N2 and SEM. The Si-Ti nanospheres did not show diffraction peaks referring to any phase of titanium oxide, indicating that the metal is actually found in the structure of the nanospheres, however for Si-Ce materials it is noticed that high amounts of Cerium can lead to unwanted CeO formation. SEM images demonstrated the formation of welldefined spheres, for both metals, with diameters between 50 and 400 nm. A uniform scattering of Ce and Ti was observed in all materials, which indicates that these metals are actually participating in the composition of the inorganic structure of the nanospheres, corroborating the results of XRD. The proposed soft-template method proved to be effective, enabling the synthesis, in a short time, of Si-Ce and Si-Ti photocatalysts. The photocatalysts showed significant activity in the degradation of Rhodamine B, with Si-Ti-based materials showing the best activity, with reductions of more than 60% of the contaminant being observed. In addition to the photocatalytic activity, the materials also demonstrated a good adsorption capacity in the first 30 minutes of reaction.