Estudio de la superficie de TiO₂−OT⁺n/HY como fotocatalizador para el tratamiento de agua contaminada con compuestos recalcitrantes
This thesis work focuses on the investigation of heterogeneous photocatalysis for the degradation and mineralization of recalcitrant organic compounds present in water. The main objective is to study the behavior of a promising catalyst that uses protonated α-oligothiophenes (OT+ n ) as sensitisers...
| Autor: | |
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| Tipo de recurso: | tesis de maestría |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:g732d963r |
| Acceso en línea: | https://doi.org/10.24275/uami.g732d963r |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Agua -- Contaminación info:eu-repo/classification/LEM/Fotocatálisis info:eu-repo/classification/LEM/Water -- Pollution info:eu-repo/classification/LEM/Photocatalysis info:eu-repo/classification/cti/7 |
| Sumario: | This thesis work focuses on the investigation of heterogeneous photocatalysis for the degradation and mineralization of recalcitrant organic compounds present in water. The main objective is to study the behavior of a promising catalyst that uses protonated α-oligothiophenes (OT+ n ) as sensitisers for TiO2 particles supported on protonated zeolite Y (TiO2 −OT+ n /HY), during the oxidation of different molecules under various electromagnetic radiation conditions, both in terms of power and wavelength of light (UV and visible). The materials synthesis was carried out using the sol-gel method, followed by sensitization with the OT+ n . The TiO2 content was varied at 20, 30, and 40% by weight to study its influence on catalyst activation and photocatalytic degradation. Structural, optical, and textural properties were analyzed using various analytical techniques. First, the TiO2 −OT+ n /HY catalysts were evaluated in the degradation of contaminants such as indigo carmine, phenol, 4-chlorophenol, and 2,4-dichlorophenol. Different batch photoreactor configurations were used. The results showed that the 40ST material completely degraded indigo carmine in just 360 minutes using a system with low-power visible light LEDs (10 W), while the reference material TiO2 −DP25 only degraded approximately 2% of indigo carmine. However, the TiO2 −OT+ n /HY catalysts were not effective in the degradation of phenolic molecules, as the 40ST material only degraded 10% of 4-chlorophenol after 360 minutes. Second, the TiO2 −OT+ n /HY catalysts were evaluated in the degradation of 2,4-dichlorophenol (2,4- DCF) using a batch-operated photoreactor. This reactor operated under UV-C light from a Pen-Ray mercury lamp with a power of 2.5 mW/cm2 at 254 nm. During the tests, an 80.21% mineralization of 2,4-DCF was achieved using the 20T catalyst. On the other hand, the 20ST catalyst achieved a 41.45% mineralization, while the TiO2 −DP25 reached 27.17%. However, it was observed that photolysis had a significant impact on the mineralization of the molecule, reaching 64.1%. Third, experiments were conducted in a batch-operated photoreactor, irradiating the material with a visible LED with a power of 100 W. It was found that the 20T material was the most effective in degrading 2,4-DCF, achieving a mineralization of up to 82.69%. Among the sensitized materials, the 20ST catalyst showed the highest mineralization (64.1%) of 2,4-DCF. Fourth, based on these results, a photoreactor was designed to evaluate the catalytic materials configured with low-power LEDs (1 W). During this analysis, it was observed that as the amount of titanium oxide in the TiO2 −OT+ n /HY catalysts increased, the percentage of mineralization gradually decreased, from 48.9% with the 20ST material to 20.58% with the 40ST material under visible light. In conclusion, it was determined that the 20ST material provided the best performance in terms of degradation, which was related to the size of titanium particles on the surface and the sensitizer. The results of photodegradation using the TiO2 −OT+ n /HY catalysts showed superior activity compared to the reference material TiO2 −DP25 (7.38%). Fifth, methanol, 1,4-benzoquinone (1,4-BZQ) and ammonium oxalate (OA) were used as sacrificial agents in the degradation of 2,4-DCF using the photoreactor equipped with low-power LEDs (1 W), operating with UV-A or visible light, along with the 20ST catalyst. By adding methanol, which captures hydroxyl radicals (•OH), it was noted that these radicals do not have a fundamental role in the degradation of the molecule, since the degradation rate decreased from 61.74% to 57.23 % under visible light. On the other hand, the addition of 1,4-BZQ inhibited the degradation reaction, highlighting superoxide radicals (O•− 2 ) as the main oxidant species in photodegradation. of 2,4-DCF. When using OA, which captures holes (h+), it was observed that these play an important role, reducing the degradation from 61.74% to 39.24% under visible light Finally, with all the results and aiming to improve the performance of the photocatalysts, a synthesis was carried out following a different methodology focused on impregnating only TiO2 into protonated zeolite Y, varying the concentration of TiO2 at 10, 15 and 20% by weight to investigate its influence on generating smaller titanium particles on the zeolite, which would allow for better photocatalytic degradation of 4-chlorophenol under UV-C irradiation. The photocatalytic evaluation of the recalcitrant molecule was performed with a Pen-Ray mercury lamp irradiating at 2.5 mW/cm2 at 254 nm. A significant impact of photolysis on degradation was observed, reaching approximately 50%. A degradation of 78.68% of 4-chlorophenol was achieved with the 15TC material, and up to 91.57% with the reference TiO2 catalyst, synthesized using the sol-gel method in just 360 minutes. The new synthesis reduced the size of the TiO2 crystallites by half (D = 16.2 nm), compared to the previous synthesis (D = 32.8 nm). These results suggest that the presence of the zeolite contributes to the proper activation of the material, due to a good distribution and dispersion of the titanium dioxide on its surface, as well as the reduced size of the crystallites. Further studies should be conducted, focusing especially on the synthesis method and the doping of titanium dioxide with other metals to improve its catalytic performance on the zeolite. |
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