Fotodegradação de corante orgânico em meio aquoso por fotocatálise plasmônica com uso de nanopartículas de Ag e TiO2
Data
2022-06-03
Autores
Helene, Gustavo [UNIFESP]
Orientadores
Pellosi, Diogo Silva [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Os processos industriais levam a uma grande contaminação de água para reuso e descarte. Os atuais tratamentos fotocatalíticos normalmente baseados em óxidos metálicos como o dióxido de titânio - TiO2 são pouco eficientes, além de absorverem luz apenas na região UV do espectro eletromagnético, o que torna o processo economicamente ineficiente. A fim de melhorar suas propriedades eletrônicas, propomos aqui funcionalizar o TiO2 com nanopartículas de prata (AgNP). A AgNP apresenta forte absorção de luz na faixa do visível, a qual depende de seu tamanho e morfologia, e sua superfície favorece processos foto/eletroquímicos na superfície do TiO2. Assim, AgNPs de diferentes tamanhos e formas (esferas, prismas e bastonetes) foram sintetizadas em água e então depositadas na superfície do TiO2 usando 3-MPA como agente de ligação. Os nanohíbridos TiO2/AgNP possuem a vantagem de apresentar elevada absorção de luz nas regiões UV e visível do espectro, serem pouco solúveis em água (catálise heterogênea) e apresentam uma lenta recombinação elétron/lacunas, aumentando a eficácia fotocatalítica. Estes foram caracterizados através de espectrofotometria UV-Vis, Difração de Raio X (DRX), Microscopia eletrônica de transmissão (MET), Infravermelho por Transformada de Fourier (FTIR), Reflectância Difusa e Fotoluminescência (FL). A relação entre otimização estrutural do nanohíbrido TiO2/AgNP e seu poder fotocatalítico foi uma questão norteadora deste trabalho. A fotocatálise foi realizada com uma lâmpada policromática de Hg (emissão UV-Vis) para a degradação do corante alaranjado de metila (MO) como modelo de poluentes orgânicos persistente em água. A descrição da cinética da fotodegradação pelo mecanismo cinético de pseudo-primeira ordem Langmuir-Hinshelwood mostrou que nanohíbridos TiO2/AgNP são significativamente mais eficientes que o TiO2 puro e que tanto tamanho quanto morfologia da AgNP são importantes na degradação do corante em água. Para TiO2/AgNP esféricas, quanto menor a AgNP, maior a eficiência fotocatalítica. Já as amostras TiO2/AgNP prisma e bastonetes se mostraram ainda mais eficientes que as esferas, por conta de um mecanismo de geração de elétrons quentes nas suas estruturas. Desta forma, demonstra-se que a adsorção de AgNPs anisotrópicas é uma forma eficiente de melhorar as propriedades fotocatalíticas do TiO2 e que o design racional e controle sobre a morfologia das AgNP é um caminho para a melhor otimização do processo.
Industrial processes lead to a large amount of water contamination for reuse and disposal. Current photocatalytic processes usually based on metallic oxides such as titanium dioxide - TiO2 are not very efficient, in addition to absorbing light only in the UV region of the electromagnetic spectrum, which makes the process economically inefficient. In order to improve its electronic properties, we propose here TiO2 functionalization with silver nanoparticles (AgNP). AgNP shows strong absorption of light in the visible range, which depends on its size and morphology. In addition, its surface favors photo/electrochemical processes on the TiO2 surface. Thus, AgNPs of different sizes and shapes (spheres, prisms and rods) were synthesized in water and then deposited on TiO2 surface using 3-MPA as a binding agent. TiO2/AgNP nanohybrids have the advantage of presenting high absorption of light in the UV and visible regions of the spectrum, being poorly soluble in water (heterogeneous catalysis) and a slow electron/hole recombination, which increases the photocatalytic efficiency. These were characterized by UV-Vis spectrophotometry, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR), Diffuse Reflectance and Photoluminescence (PL). The relationship between structural optimization of the TiO2/AgNP nanohybrid and its photocatalytic power was a guiding question in this work. Photocatalysis was performed with a polychromatic Hg lamp (UV-Vis emission) for the degradation of the methyl orange (MO) dye as a model of organic pollution in water. The photodegradation kinetics followed Langmuir-Hinshelwood pseudo-first order kinetic mechanism and showed that TiO2/AgNP nanohybrids are significantly more efficient than pure TiO2 and that both size and morphology are important in the degradation of the dye in water. For spherical TiO2/AgNP, the lower the AgNP, the higher the photocatalytic efficiency. The TiO2/AgNP prism and rods samples were even more efficient than the spheres, due to a mechanism of generation of hot electrons on the AgNP surface. Therefore, the present work demonstrated that adsorption of anisotropic AgNPs is an efficient way to improve the photocatalytic properties of TiO2 and that the rational design and control over the morphology of AgNP can optimize the process.
Industrial processes lead to a large amount of water contamination for reuse and disposal. Current photocatalytic processes usually based on metallic oxides such as titanium dioxide - TiO2 are not very efficient, in addition to absorbing light only in the UV region of the electromagnetic spectrum, which makes the process economically inefficient. In order to improve its electronic properties, we propose here TiO2 functionalization with silver nanoparticles (AgNP). AgNP shows strong absorption of light in the visible range, which depends on its size and morphology. In addition, its surface favors photo/electrochemical processes on the TiO2 surface. Thus, AgNPs of different sizes and shapes (spheres, prisms and rods) were synthesized in water and then deposited on TiO2 surface using 3-MPA as a binding agent. TiO2/AgNP nanohybrids have the advantage of presenting high absorption of light in the UV and visible regions of the spectrum, being poorly soluble in water (heterogeneous catalysis) and a slow electron/hole recombination, which increases the photocatalytic efficiency. These were characterized by UV-Vis spectrophotometry, X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR), Diffuse Reflectance and Photoluminescence (PL). The relationship between structural optimization of the TiO2/AgNP nanohybrid and its photocatalytic power was a guiding question in this work. Photocatalysis was performed with a polychromatic Hg lamp (UV-Vis emission) for the degradation of the methyl orange (MO) dye as a model of organic pollution in water. The photodegradation kinetics followed Langmuir-Hinshelwood pseudo-first order kinetic mechanism and showed that TiO2/AgNP nanohybrids are significantly more efficient than pure TiO2 and that both size and morphology are important in the degradation of the dye in water. For spherical TiO2/AgNP, the lower the AgNP, the higher the photocatalytic efficiency. The TiO2/AgNP prism and rods samples were even more efficient than the spheres, due to a mechanism of generation of hot electrons on the AgNP surface. Therefore, the present work demonstrated that adsorption of anisotropic AgNPs is an efficient way to improve the photocatalytic properties of TiO2 and that the rational design and control over the morphology of AgNP can optimize the process.