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Abstract(s)
Este trabalho tem como principal objectivo preparar e caracterizar ânodos de Ti/Pt/SnO2-Sb2Ox e estudar a sua aplicação na degradação de compostos orgânicos persistentes, bem como comparar estes resultados com os resultados obtidos com o ânodo comercial de BDD.
Foram preparados dois ânodos, Ti/Pt/SnO2-Sb2Ox (4) e Ti/Pt/SnO2-Sb2Ox (16). Na preparação destes, o substrato (titânio) foi platinizado de modo a optimizar o tempo de vida útil, após este passo foram feitas electrodeposições de estanho e antimónio, alternadamente, e por fim, uma etapa de calcinação, para formação dos respectivos óxidos. A preparação destes ânodos é muito semelhante com excepção do número de camadas depositadas alternadamente de cada metal, que num eléctrodo é de 4 e noutro de 16. Foi efectuada a caracterização estrutural, morfológica, química e electroquímica do eléctrodo, recorrendo a várias técnicas, como difracção de raios X, microscopia electrónica de varrimento, espectroscopia de dispersão de energias e voltametria cíclica.
Numa segunda fase, realizou-se o estudo da aplicabilidade destes eléctrodos, como ânodos, na electrodegradação de fármacos comuns, como o Naproxeno, Diclofenac, Ibuprofeno, Ácido Clofíbrico e Amoxicilina, usando-se soluções aquosas do fármaco 100 ppm e tendo como electrólito suporte o Na2SO4 5 g L-1. Este estudo foi efectuado a três densidades de corrente diferentes 10, 20 e 30 mA cm-2.
Todos os ensaios de electrodegradação foram monitorizados através de determinações da Carência Química de Oxigénio e do Carbono Orgânico Total e por Espectrofotometria de UltraVioleta/Vísivel.
Em relação aos materiais de eléctrodo, na maioria das situações, o ânodo Ti/Pt/SnO2-Sb2Ox(4) é o que apresenta melhores resultados entre os dois ânodos de óxidos, além de que a energia consumida na preparação do ânodo Ti/Pt/SnO2-Sb2Ox(16) é significativamente superior à do eléctrodo Ti/Pt/SnO2-Sb2Ox(4). Tendo em conta os três materiais de eléctrodo, o ânodo de BDD comercial é o que apresenta melhores remoções de CQO, TOC e Abs, mas é o material mais dispendioso. Os ânodos de Ti/Pt/SnO2-Sb2Ox são muito mais económicos sendo por isso fundamental estudar formas de melhorar a sua eficiência na degradação de poluentes.
Relativamente a resultados obtidos em trabalhos anteriores, com ânodos de SnO2-Sb2Ox é importante dizer que a platinização prévia do substrato antes da electrodeposição dos metais aumentou bastante o tempo de vida dos eléctrodos.
The purpose of this work is to prepare and characterize Ti/Pt/SnO2-Sb2Ox anodes and to study their application in the degradation of persistent organic compounds, as well as compare these results with those obtained with the commercial BDD anode. Two types of anodes, Ti/Pt/SnO2-Sb2Ox (4) and Ti/Pt/SnO2-Sb2Ox (16), were prepared. In their preparation, the substrate (titanium) was platinized, to optimize its lifetime, prior to the tin and antimony alternate electrodepositions. The last step was the calcination stage, for the formation of the respective oxides. The preparation of these anodes is very similar, with the exception of the number of layers deposited alternatively on each metal that were, respectively, 4 and 16. The structural, morphological, chemical and electrochemical characterizations of the electrode were done, using various techniques, namely X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and cyclic voltammetry. In a second part, the study of the applicability of these electrodes, as anodes, in the electrodegradation of common drugs was performed. Drugs used were Naproxen, Diclofenac, Ibuprofen, Clofibric Acid and Amoxicillin, in aqueous solution with 100 ppm concentration and having Na2SO4 5 g L-1 as the electrolyte support. This study was done at three different current densities, 10, 20 and 30 mA cm-2 . All electrodegradation assays were monitorized by the COD and TOC determinations and by spectrophotometry of ultraviolet / visible. Among the prepared oxide materials, Ti/Pt/SnO2-Sb2Ox(4) presents the best results in the rate of degradation of the organic compounds. Besides that, the energy consumption in the preparation of this electrode is substantially lower than that of Ti/Pt/SnO2-Sb2Ox(16) electrode . However, when the three electrode materials are compared, the commercial BDD anode is the one that presents the best removals for COD, TOC and Abs., but it is also the most expensive material. Since Ti/Pt/SnO2-Sb2Ox anodes are cheaper and proved to have a good performance in the degradation of organic pollutants, it is necessary to pursue this study in order to improve their efficiency in pollution abatement. Regarding lifetime, it is important to refer that the previous platinization of the substrate, prior to the electrodeposition of the metals, increased greatly the mechanical and electrochemical stabilities of the electrodes, when compared to that of SnO2-Sb2Ox anodes.
The purpose of this work is to prepare and characterize Ti/Pt/SnO2-Sb2Ox anodes and to study their application in the degradation of persistent organic compounds, as well as compare these results with those obtained with the commercial BDD anode. Two types of anodes, Ti/Pt/SnO2-Sb2Ox (4) and Ti/Pt/SnO2-Sb2Ox (16), were prepared. In their preparation, the substrate (titanium) was platinized, to optimize its lifetime, prior to the tin and antimony alternate electrodepositions. The last step was the calcination stage, for the formation of the respective oxides. The preparation of these anodes is very similar, with the exception of the number of layers deposited alternatively on each metal that were, respectively, 4 and 16. The structural, morphological, chemical and electrochemical characterizations of the electrode were done, using various techniques, namely X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and cyclic voltammetry. In a second part, the study of the applicability of these electrodes, as anodes, in the electrodegradation of common drugs was performed. Drugs used were Naproxen, Diclofenac, Ibuprofen, Clofibric Acid and Amoxicillin, in aqueous solution with 100 ppm concentration and having Na2SO4 5 g L-1 as the electrolyte support. This study was done at three different current densities, 10, 20 and 30 mA cm-2 . All electrodegradation assays were monitorized by the COD and TOC determinations and by spectrophotometry of ultraviolet / visible. Among the prepared oxide materials, Ti/Pt/SnO2-Sb2Ox(4) presents the best results in the rate of degradation of the organic compounds. Besides that, the energy consumption in the preparation of this electrode is substantially lower than that of Ti/Pt/SnO2-Sb2Ox(16) electrode . However, when the three electrode materials are compared, the commercial BDD anode is the one that presents the best removals for COD, TOC and Abs., but it is also the most expensive material. Since Ti/Pt/SnO2-Sb2Ox anodes are cheaper and proved to have a good performance in the degradation of organic pollutants, it is necessary to pursue this study in order to improve their efficiency in pollution abatement. Regarding lifetime, it is important to refer that the previous platinization of the substrate, prior to the electrodeposition of the metals, increased greatly the mechanical and electrochemical stabilities of the electrodes, when compared to that of SnO2-Sb2Ox anodes.
Description
Keywords
Compostos farmacêuticos Naproxen Electrodegradação Amoxicilina