Discoloration of alizarin red on thin films of Fe (III)-tetracarboxyphenyl porphyrin deposited on silicon oxide
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Universidad Santo Tomás. Seccional Bucaramanga
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El rojo de alizarina es un colorante de antraquinona soluble en agua que se usa ampliamente en la industria textil como agente de tinción y se considera uno de los contaminantes más recalcitrantes y duraderos. La reacción de Fenton puede usarse para destruir una amplia variedad de compuestos orgánicos: un ion ferroso reacciona con el peróxido de hidrógeno (H2O2) para formar un radical hidroxilo (HO•) que es un poderoso agente oxidante. La velocidad de esta reacción podría aumentarse cuando se expone a la luz UV-Vis, este método se conoce como proceso de Foto-Fenton y constituye una alternativa atractiva a los procesos de oxidación avanzada. En este trabajo se estudió la decoloración fotocatalítica del colorante rojo de alizarina mediante un proceso Foto-Fenton heterogéneo inducido por luz visible; para tal fin, se utilizaron películas delgadas de tetra(4-carboxifenil) porfirina de hierro (III) adsorbidas sobre dióxido de silicio. La caracterización del catalizador fue realizada por UV-Vis, reflectancia difusa e IR-FT. Los ensayos fueron realizados a tres (3) valores de pH 1.0, 3.0 y 5.0; finalmente, se utilizó el modelo cinético descrito por Langmuir-Hinshelwood para obtener los parámetros cinéticos del proceso de fotodecoloración. Los resultados mostraron que la mayor decoloración del rojo de alizarina se presentó a un pH de 1.0; además, el modelo de pseudo-primer orden aplicado permitió obtener la constante de velocidad (k) del proceso de decoloración encontrando que el mayor valor de k fue 1.1x10-2 min-1. Los radicales hidroxilo se detectaron por atrapamiento químico a través de fluorescencia indirecta del ácido 2-hidroxitereftálico. Los procesos de foto-Fenton basados en sistemas de catálisis heterogénea resuelven parte de estos problemas ambientales, proporcionando una fácil separación y recuperación del catalizador de las aguas residuales tratadas, en el que no es corrosivo y, además, es ecológico.
Alizarin Red is a water soluble anthraquinone dye used extensively in the textile industry as a staining agent and is considered to be one of the most recalcitrant and durable pollutants. Fenton reaction can be used to destroy a wide variety of organic compounds: a ferrous ion reacts with hydrogen peroxide (H2O2) to form hydroxyl radical (HO•) which is a powerful oxidizing agent. The rate of this reaction could be increased when exposed o UV–vis light, this method is known as photo-assisted Fenton process and constitutes an attractive alternative of advance oxidation process. In this work, we studied the alizarin red dye photocatalytic discoloration through heterogeneous Photo-Fenton process induced by visible light; we used tetra (4-carboxyphenyl) porphyrin iron (III) adsorbed on silicon dioxide thin films. The characterization of the catalyst was carried out by UV-Vis, diffuse reflectance and IR-FT; The tests were carried out at three (3) pH values 1.0, 3.0 and 5.0; finally, the kinetic model described by Langmuir-Hinshelwood was used to obtain kinetic parameters for photo-discoloration process. The results showed that at pH = 1.0 highest alizarin red photo-discoloration percentage was reported; furthermore, after applied the pseudo-first order model, we obtained rate constants (k) for discoloration process that finds the highest k value was 1.1x10-2 min-1. The hydroxyl radicals were detected by chemical trapping through indirect fluorescence of the 2-hydroxyterephthalic acid. Photo-Fenton processes based on heterogeneous catalysis systems solve part of these environmental problems providing an easy separation and recovery of the catalyst from the treated wastewater, wherein it is noncorrosive, and, besides, it is environmentally friendly.
Alizarin Red is a water soluble anthraquinone dye used extensively in the textile industry as a staining agent and is considered to be one of the most recalcitrant and durable pollutants. Fenton reaction can be used to destroy a wide variety of organic compounds: a ferrous ion reacts with hydrogen peroxide (H2O2) to form hydroxyl radical (HO•) which is a powerful oxidizing agent. The rate of this reaction could be increased when exposed o UV–vis light, this method is known as photo-assisted Fenton process and constitutes an attractive alternative of advance oxidation process. In this work, we studied the alizarin red dye photocatalytic discoloration through heterogeneous Photo-Fenton process induced by visible light; we used tetra (4-carboxyphenyl) porphyrin iron (III) adsorbed on silicon dioxide thin films. The characterization of the catalyst was carried out by UV-Vis, diffuse reflectance and IR-FT; The tests were carried out at three (3) pH values 1.0, 3.0 and 5.0; finally, the kinetic model described by Langmuir-Hinshelwood was used to obtain kinetic parameters for photo-discoloration process. The results showed that at pH = 1.0 highest alizarin red photo-discoloration percentage was reported; furthermore, after applied the pseudo-first order model, we obtained rate constants (k) for discoloration process that finds the highest k value was 1.1x10-2 min-1. The hydroxyl radicals were detected by chemical trapping through indirect fluorescence of the 2-hydroxyterephthalic acid. Photo-Fenton processes based on heterogeneous catalysis systems solve part of these environmental problems providing an easy separation and recovery of the catalyst from the treated wastewater, wherein it is noncorrosive, and, besides, it is environmentally friendly.
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Porphyrin, photo-fenton hydroxyl radical, alizarin red dye, visible light, catalysis, Porfirina, foto-Fenton, radical hidroxilo, rojo de alizarina, luz visible, catálisis
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