DESENVOLVIMENTO DE NANOMATERIAIS FOTOATIVOS À BASE DE TITÂNIO PARA FOTOGERAÇÃO DE H2 E FOTODEGRADAÇÃO DO IBUPROFENO

Abstract

Advanced Oxidation Processes (AOPs) generate oxidative radicals, such as the hydroxyl radical (HO•), which are fundamental in the degradation of emerging contaminants not removed by conventional methods. Among AOPs, heterogeneous photocatalysis with TiO 2 stands out due to its high photocatalytic activity, stability, and low cost. In this context, this research developed, characterized, and applied two types of titanium-based nanomaterials: (1) TiO 2 derived from the calcination of the MOFs (MOF = metal-organic frameworks) MIL- 125(Ti) (MIL = Materials Institute Lavoisier) and 2,5-PDC-MIL-125(Ti); and (2) TiO 2 supported on biochar (BC), obtained from orange peel (Citrus sinensis) and grapevine branches (Vitis vinifera). These materials were designed to meet two main applications: (i) hydrogen (H 2 ) photogeneration, a clean and renewable fuel, through glycerol oxidation, and (ii) photodegradation of emerging contaminants, using the pharmaceutical ibuprofen as a model contaminant. For the preparation of the metal-organic structures, a solvothermal reactor was used, and the formed structure was calcined at 450 ºC, converting the MOFs into TiO 2 compounds. Biochar was obtained with and without a nitrogen atmosphere. The TiO 2 was supported on BCs and also calcined at 450 ºC. The titanium-based materials exhibited properties favorable for their application, including high thermal stability and a porous structure efficient for H 2 photogeneration, a reaction in which glycerol was used as an electron donor. The highest efficiency was observed at pH 6, generating 0.31 µmol of H₂ in 240 minutes for the MOF/TiO 2 material, while the 2,5-PDC-MOF/TiO 2 generated 0.25 µmol of H₂, along with the formation of by-products such as glyceraldehyde and dihydroxyacetone. In ibuprofen photodegradation experiments, at different TiO 2 /BC ratios, the best results were obtained with the 1:0.1 ratio using grapevine branch BC, removing 87% of the ibuprofen. This demonstrates that replacing part of the TiO 2 with BC does not cause a loss of efficiency, reducing operational costs and proving to be a viable alternative for environmental treatments with excellent potential for large-scale applications. During photogeneration experiments, a higher (basic) pH favored the selectivity for dihydroxyacetone, due to the greater stability of the oxidative intermediates. Both materials were characterized by advanced techniques, such as UV-VIS DRS (Diffuse Reflectance Spectroscopy in UV-Vis), FTIR-ATR (Fourier Transform Infrared Spectroscopy with Attenuated Total Reflectance), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), TG (Thermogravimetric Analysis), XPS (X-ray Photoelectron Spectroscopy), XRD (X-ray Diffraction), and BET (Brunauer, Emmett, and Teller), which confirmed their structural, thermal, and photocatalytic properties. The analyses showed that the MOF was modified, resulting in TiO 2 . The carboxylate stretching (COO−) indicated that the ligands were destroyed in both MOFs, allowing the formation of TiO₂. The surface area of the MOF/TiO 2 photocatalyst is 376 m²g⁻¹ and, after calcination, it resulted in 59 m²g⁻¹. XRD showed characteristic peaks of TiO 2 in the anatase and rutile phases. For the materials supported on biochars, the surface area of TiO 2 /BC (90.31 m²g⁻¹ for the 1:0.5 LN ratio) was higher than that of pure TiO 2 (18.94 m²g⁻¹). The band gap energy (Ebg) of the TiO₂/BC materials was approximately 3.11 and 3.15 eV. The results obtained confirm that titanium-based materials are promising solutions for clean energy generation and environmental remediation.