Photocatalytic degradation of ibuprofen using modified titanium oxide supported on CMK-3: effect of Ti content on the TiO2 and carbon interaction

Abstract

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 theoretical–computational study through single point energy calculations was also presented. 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 I_D/I_G 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 calculations confirmed the lowest energy to stabilize the titanium oxide and carbon composite for the sample with 1% of Ti compared to 8 and 18%. The 1% Ti₂O/CMK-3 photocatalyst exhibited the best photocatalytic performance, reaching 100% degradation in just 5 min. 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 solution and on the solid surface, and may lead to the formation of intermediates before its mineralization.