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Modificação de zeólitos para a degradação de azul de metileno por reações tipo Fenton
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Abstract(s)
A presente dissertação teve como principal objetivo a modificação de zeólitos para a degradação de azul de metileno por reações tipo Fenton. Nesta modificação das estruturas zeóliticas foram estudadas diferentes vias de incorporação do ião metálico, mecanoquímica e permuta iónica, fundamental para a formação dos radicais hidroxilo responsáveis pela degradação da molécula modelo. A razão Si/Al dos zeólitos também foi alterada em algumas amostras, através de dessilicação seguida de um tratamento ácido. Os zeólitos modificados foram posteriormente caraterizados por meio de diferentes técnicas como difração de raios-X para a determinação da percentagem de cristal, adsorção com N2 a – 196 ºC para determinação dos parâmetros texturais, a composição química das amostras foi determinada por espectrometria de emissão atómica por plasma acoplado indutivamente (ICP-OES). Paralelamente, na presente dissertação são apresentados alguns resultados de ensaios preliminares com o método mecanoquímico provenientes do projeto ZeoMed referente à Bolsa de Iniciação à Investigação com a Refª IPL/2022/ZeoMed_ISEL/BII/5M, que tiveram como objetivo a otimização das condições reacionais da mecanoquímica. Além das caraterizações já citadas, foi ainda também analisado o tamanho de partícula por difração laser através do método de dispersão húmida, usando água como agente dispersante. A quantificação do corante azul de metileno foi feita por espetrofotometria UV-Visível, sendo que o processo de gradual desaparecimento da cor foi monitorizado por medidas de absorvância do meio reacional a diferentes tempos. Foi obtida uma curva de calibração que corresponde à variação da absorvância no comprimento de onda de 663 nm com a concentração da solução. Para averiguar a capacidade da reação de Fenton, foram aplicados modelos cinéticos de pseudo-primeira e pseudo-segunda ordem, para obtenção de constantes cinéticas que permitem avaliar os tratamentos induzidos na modificação das estruturas zeolíticas. Além de ter sido estudado o fenómeno de adsorção por meio de isotérmicas de adsorção.
Abstract The main objective of this dissertation was to modify zeolites for the degradation of methylene blue by Fenton-type reactions. In this modification of the zeolite structures, different pathways of incorporation of the metal ion, mechanochemistry and ion exchange, fundamental for the formation of the hydroxyl radicals responsible for the degradation of the model molecule, were studied. The Si/Al ratio of the zeolites was also altered in some samples, through desilication followed by an acid treatment. The modified zeolites were subsequently characterized by means of different techniques such as X-ray diffraction to determine the percentage of crystals, adsorption with N2 at -196 ºC to determine the textural parameters, the chemical composition of the samples was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES). In parallel, this dissertation presents some results of preliminary tests with the mechanochemical method from the ZeoMed project related to the Research Initiation Grant with Ref. IPL/2022/ZeoMed_ISEL/BII/5M, which aimed to optimize the reaction conditions of mechanochemistry. In addition to the aforementioned characterizations, the particle size was also analyzed by laser diffraction using the wet dispersion method, using water as a dispersing agent. The quantification of the methylene blue dye was done by UV-Visible spectrophotometry, and the process of gradual color disappearance was monitored by absorbance measurements of the reaction medium at different times. A calibration curve was obtained that corresponds to the variation of absorbance at the wavelength of 663 nm with the concentration of the solution. To assess the capacity of the Fenton reaction, pseudo-first and pseudo-second order kinetic models were applied to obtain kinetic constants that allow the evaluation of the treatments induced in the modification of the zeolitic structures. In addition, the adsorption phenomenon was studied by means of adsorption isotherms.
Abstract The main objective of this dissertation was to modify zeolites for the degradation of methylene blue by Fenton-type reactions. In this modification of the zeolite structures, different pathways of incorporation of the metal ion, mechanochemistry and ion exchange, fundamental for the formation of the hydroxyl radicals responsible for the degradation of the model molecule, were studied. The Si/Al ratio of the zeolites was also altered in some samples, through desilication followed by an acid treatment. The modified zeolites were subsequently characterized by means of different techniques such as X-ray diffraction to determine the percentage of crystals, adsorption with N2 at -196 ºC to determine the textural parameters, the chemical composition of the samples was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES). In parallel, this dissertation presents some results of preliminary tests with the mechanochemical method from the ZeoMed project related to the Research Initiation Grant with Ref. IPL/2022/ZeoMed_ISEL/BII/5M, which aimed to optimize the reaction conditions of mechanochemistry. In addition to the aforementioned characterizations, the particle size was also analyzed by laser diffraction using the wet dispersion method, using water as a dispersing agent. The quantification of the methylene blue dye was done by UV-Visible spectrophotometry, and the process of gradual color disappearance was monitored by absorbance measurements of the reaction medium at different times. A calibration curve was obtained that corresponds to the variation of absorbance at the wavelength of 663 nm with the concentration of the solution. To assess the capacity of the Fenton reaction, pseudo-first and pseudo-second order kinetic models were applied to obtain kinetic constants that allow the evaluation of the treatments induced in the modification of the zeolitic structures. In addition, the adsorption phenomenon was studied by means of adsorption isotherms.
Description
Dissertação para obtenção do grau de Mestre em Engenharia Química e Biológica, na Área de Especialização de Processos Químicos
Keywords
Catalisador Reações de Fenton Adsorção Ião metálico Degradação Catalyst Fenton reactions Adsorption Metal ion Degradation
Citation
COSTA, José Tiago Nunes da –Modificação de zeólitos para a degradação de azul de metileno por reações tipo Fenton. Lisboa: Instituto Superior de Engenharia de Lisboa. 2024. Dissertação de Mestrado.COSTA, José Tiago Nunes da –Modificação de zeólitos para a degradação de azul de metileno por reações tipo Fenton. Lisboa: Instituto Superior de Engenharia de Lisboa. 2024. Dissertação de Mestrado.