Degradação fotocatalítica do Ibuprofeno usando nanopartículas de Titânio suportada em Carbono Cmk-3 Mesoporoso

Abstract

This work addresses the role of TiO2 nanoparticles dispersed in ordered mesoporous CMK-3 carbon with different Ti, contents were successfully synthesized and their activity in the photocatalytic degradation of ibuprofen was presented. The photocatalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, diffuse reflectance, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM-FEG) and transmission electron microscopy (TEM). A simple theoreticalcomputational study through the point energy calculation was presented to evaluate the interaction between the TiO2-C and also another study using the DFT approach to estimate the preferred attack region for OH• radical. Diffractograms, Raman, and XPS spectra confirmed the formation of anatase and graphitic carbon. Low-angle XRD, N2 physisorption and the TEM images indicated that the CMK-3 support does not undergo a significant change in the mesoporous structure after the insertion of TiO2. The ID/IG ratio observed in the Raman spectra did not vary significantly with an increase in the titanium content, which shows that the crystallinity of CMK-3 is practically unchanged. Anatase crystallite sizes vary from 8 to 15 nm and specific areas vary from 348 to 586 m2.g-1, depending on the TiO2 content. The single point energy calculation confirmed that the interaction energy between titanium oxide and carbon increases with the increase in the amount of Ti. Chemical oxygen demand and total organic carbon results confirmed the mineralization of ibuprofen. The degradation and mineralization mechanism of ibuprofen follows a sequence of radical reactions that occur in solid-liquid interface, and may lead to the formation of intermediates before its mineralization. The 1% TiO2/CMK-3 photocatalyst exhibited the best photocatalytic performance, reaching 100% degradation in just 5 min. Different by-products have been identified by GC-MS such as 4-isobutylacetophenone. The simple study using the DFT approach demonstrated that the OH• radical attacks preferentially in the region with high electronic density of the ibuprofen molecule due to its lower free energy, which is located close to aromatic ring (C = C bond). The presence of the OH• radical was confirmed through a model reaction using salicylic acid as probe molecule.