Degradação de hormônios por processos Fenton mediados por ciclodextrina
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Data
2010-06-24
Autores
Gama, Mariana Roberto [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O estudo de interferentes endócrinos em águas tem sido relevante devido aos efeitos deletérios promovidos por estes compostos, encontrados no ambiente em baixíssimas concentrações, na faixa de ng L-1 até μg L-1. Hormônios estrógenos são importantes interferentes endócrinos. Neste trabalho, foi avaliada a influência da β- ciclodextrina (β-CD) na degradação dos hormônios estrógenos 17β-estradiol (E2) e 17α-etinilestradiol (EE2) por processo Fenton e foto-Fenton, com irradiação artificial. Por meio de métodos espectrofotométricos, determinou-se que a estequiometria de inclusão de E2:β-CD e EE2: β-CD é 1:1, e a constante de inclusão assume valores da ordem de 103 L mol-1 para ambos os hormônios. A constante de complexação Fe2+-β-CD apresentou maior valor em pH 4,0, quando comparados aos valores encontrados em pH 2,5 e 6,0. Já a constante de complexação Fe3+-β-CD foi maior em pH 6,0. A degradação de E2 e EE2 foi determinada por cromatografia líquida de alta eficiência (CLAE) e a mineralização por determinações de carbono orgânico total (COT). Foi observado que o processo Fenton (Fe2+ = 0,01 mmol L-1 e H2O2 = 0,5 mmol L-1) em pH 2,5 e 4,0 reduziu a concentração do EE2 a valores abaixo do limite de detecção do equipamento após 90 minutos de reação e em pH 6,0, a redução na concentração alcançou somente 50% após o mesmo tempo; entretanto, não ocorreu a remoção do COT das amostras, indicando que houve a formação de intermediários de reação. Na presença de β-CD, a eficiência da reação de Fenton foi menor e a redução na concentração de EE2 chegou a cerca de 50% nos valores de pH testados. Novamente, não foi observada remoção do COT das amostras. Observou-se que a degradação do EE2 por processo foto-Fenton reduz a concentração do hormônio até abaixo do limite de detecção do equipamento após 30 minutos de reação...
The study of endocrine disruptors in water has been important due to the deleterious effects promoted by these compounds, found in the environment at very low concentrations. Estrogens are important endocrine disruptors. In this study, the influence of β-cyclodextrin (β-CD) in the degradation of the hormones estrogen 17β- estradiol (E2) and 17α-ethinylestradiol (EE2) by Fenton and photo-Fenton process using artificial irradiation was evaluated. Using spectrophotometric methods, it was determined that the stoichiometry of the inclusion of E2 and EE2 in β-CD is 1:1, and the inclusion constant assumes values around 103 L mol-1 for both hormones. The Fe2+-β-CD complexation showed the highest value at pH 4.0, which was compared to values found at pH 2.5 and 6.0. The Fe2+-β-CD complexation was higher at pH 6.0. The degradation of E2 and EE2 was determined by high performance liquid chromatography and mineralization by determination of total organic carbon (TOC). It was observed that the Fenton process (Fe2+ = 0,01 mmol L-1 e H2O2 = 0,5 mmol L-1) at pH 2.5 and 4.0 reduced the concentration of EE2 to values below the detection limit of the equipment after 90 minutes of reaction and at pH 6.0, the reduction in the concentration reaches only 50% after same time. However, the removal of TOC of the samples is not observed, indicating the formation of intermediates. In the presence of β-CD, the reaction efficiency is reduced and the reduction in the concentration of EE2 reaches about 50% at the pH values tested. Again, there was no mineralization of the samples. It was observed that the degradation of EE2 by photo-Fenton process reduces the concentration of the hormone to levels below the detection limit of the equipment after 30 minutes of reaction at pH 2.5 and 4.0 and about 60% degradation is observed after 60 minutes reaction at pH 6.0. The mineralization in these samples reached... (Complete abstract click electronic access below)
The study of endocrine disruptors in water has been important due to the deleterious effects promoted by these compounds, found in the environment at very low concentrations. Estrogens are important endocrine disruptors. In this study, the influence of β-cyclodextrin (β-CD) in the degradation of the hormones estrogen 17β- estradiol (E2) and 17α-ethinylestradiol (EE2) by Fenton and photo-Fenton process using artificial irradiation was evaluated. Using spectrophotometric methods, it was determined that the stoichiometry of the inclusion of E2 and EE2 in β-CD is 1:1, and the inclusion constant assumes values around 103 L mol-1 for both hormones. The Fe2+-β-CD complexation showed the highest value at pH 4.0, which was compared to values found at pH 2.5 and 6.0. The Fe2+-β-CD complexation was higher at pH 6.0. The degradation of E2 and EE2 was determined by high performance liquid chromatography and mineralization by determination of total organic carbon (TOC). It was observed that the Fenton process (Fe2+ = 0,01 mmol L-1 e H2O2 = 0,5 mmol L-1) at pH 2.5 and 4.0 reduced the concentration of EE2 to values below the detection limit of the equipment after 90 minutes of reaction and at pH 6.0, the reduction in the concentration reaches only 50% after same time. However, the removal of TOC of the samples is not observed, indicating the formation of intermediates. In the presence of β-CD, the reaction efficiency is reduced and the reduction in the concentration of EE2 reaches about 50% at the pH values tested. Again, there was no mineralization of the samples. It was observed that the degradation of EE2 by photo-Fenton process reduces the concentration of the hormone to levels below the detection limit of the equipment after 30 minutes of reaction at pH 2.5 and 4.0 and about 60% degradation is observed after 60 minutes reaction at pH 6.0. The mineralization in these samples reached... (Complete abstract click electronic access below)
Descrição
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Quimica analitica, Contaminantes, Processos oxidativos avançados, Contaminantes ambientais, Analytical chemistry
Como citar
GAMA, Mariana Roberto. Degradação de hormônios por processos Fenton mediados por ciclodextrina. 2010. 142 f. Dissertação (mestrado) - Universidade Estadual Paulista, Instituto de Química, 2010.