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Num mundo arrebatado pela crise económica global e em busca de uma solução para este problema crescente, muitas vezes ficam esquecidas temáticas de igual importância, como é o caso da Poluição, cuja minimização é fundamental para o equilíbrio do nosso ecossistema e o consequente bem-estar de todos os seres vivos. A poluição é um problema que afeta todo o globo na generalidade, sendo ela a principal responsável pela maioria das alterações no nosso ecossistema. Dentro desta problemática, enquadra-se a poluição aquática com especial enfase para a acumulação de poluentes persistentes neste meio. Este tipo de poluentes, onde estão enquadrados compostos como fármacos, aminas aromáticas ou corantes, entre outros, são muito prejudiciais para o ambiente, devido à sua difícil degradação/mineralização. Do ponto de vista económico, os processos de tratamento de efluentes mais vantajosos e também os mais utilizados são os processos biológicos, mas devido ao facto de muitos destes poluentes serem resistentes a este tipo de tratamento, os processos eletroquímicos têm vindo a ganhar terreno devido aos resultados promissores alcançados com estas técnicas.
Neste trabalho foi abordada a degradação/mineralização de um “poluente modelo” o corante azo Acid Orange 7 (AO7) através da aplicação de uma técnica eletroquímica, a oxidação anódica, em que se utilizaram elétrodos de dióxido de titânio como ânodo, preparados por pulverização catódica DC, sobre substrato de titânio e substrato de titânio platinizado. Realizaram-se estudos de eletrodegradação do corante a diferentes densidades de corrente bem como a diferentes concentrações iniciais do poluente.
Os ensaios realizaram-se numa célula eletroquímica que opera em modo “batch” com agitação, com um elétrodo dióxido de titânio como ânodo, um elétrodo de aço inoxidável como cátodo e um elétrodo de referência Ag/AgCl,KClsat, à temperatura ambiente e com o sulfato de sódio como eletrólito suporte. As amostras recolhidas durante os ensaios foram analisadas quanto à Carência Química de Oxigénio (CQO), ao teor de Carbono Orgânico Total (COT) e foi também efetuada a análise por espectrofotometria de Absorção UV-Visível.
As melhores remoções de CQO obtidas variaram entre os 26% e os 56%, e as remoções de absorvência, medidas a 484 nm variaram entre os 11% e os 94%, para os ânodos de TiO2 não platinizado e o platinizado, respetivamente. Os valores de COT mantiveram-se praticamente inalterados durante os ensaios.
In a world dominated by the global economic crisis and searching for a solution to this growing problem, issues of equal importance, as the case of pollution remediation, crucial to the balance of our ecosystem and the wellbeing of all living beings, are often forgotten. Pollution is a problem that affects the earth in general. It is the main responsible for the majority of the changes in our ecosystem. Water pollution fits within this problematic, with special emphasis to the accumulation of persistent pollutants in the environment. This type of pollutants, which includes pharmaceutical drugs, dyes and aromatic amines, among others, are very harmful to the environment due to their difficult degradation/combustion. From the economic point of view, the most advantageous and the most used treatment processes are the biological, but due to the fact that many of these pollutants are resistant to this treatment, the application of electrochemical processes being extensively studied, due to the promising results achieved with these techniques. This work aimed to perform the degradation/mineralization of a "model pollutant" the azo dye Acid Orange 7 (AO7) through an electrochemical technique, anodic oxidation, in which titanium dioxide electrodes were used as anode after being prepared on titanium substrate and platinized titanium substrate by DC magnetron sputtering. AO7 eletrodegradation studies were performed at different current densities and at different initial pollutant concentrations. Assays were carried out in an electrochemical cell that operates in "batch" mode with stirring, using a titanium dioxide electrode as anode, a stainless steel electrode as cathode and a reference electrode of Ag/AgCl,KClsat. Assays were run at room temperature and using sodium sulfate as supporting electrolyte. The samples collected during the tests were analyzed for chemical oxygen demand (COD), and for Total Organic Carbon (TOC) content. Analysis by UV-Visible absorption spectrophotometry was also performed. The best values of COD removals were 26% and 56% and the highest absorvance removals at 484 nm, were 11% and 94%, for the TiO2 platinized and not platinized anodes, respectively. TOC values remained almost unchanged throughout the tests.
In a world dominated by the global economic crisis and searching for a solution to this growing problem, issues of equal importance, as the case of pollution remediation, crucial to the balance of our ecosystem and the wellbeing of all living beings, are often forgotten. Pollution is a problem that affects the earth in general. It is the main responsible for the majority of the changes in our ecosystem. Water pollution fits within this problematic, with special emphasis to the accumulation of persistent pollutants in the environment. This type of pollutants, which includes pharmaceutical drugs, dyes and aromatic amines, among others, are very harmful to the environment due to their difficult degradation/combustion. From the economic point of view, the most advantageous and the most used treatment processes are the biological, but due to the fact that many of these pollutants are resistant to this treatment, the application of electrochemical processes being extensively studied, due to the promising results achieved with these techniques. This work aimed to perform the degradation/mineralization of a "model pollutant" the azo dye Acid Orange 7 (AO7) through an electrochemical technique, anodic oxidation, in which titanium dioxide electrodes were used as anode after being prepared on titanium substrate and platinized titanium substrate by DC magnetron sputtering. AO7 eletrodegradation studies were performed at different current densities and at different initial pollutant concentrations. Assays were carried out in an electrochemical cell that operates in "batch" mode with stirring, using a titanium dioxide electrode as anode, a stainless steel electrode as cathode and a reference electrode of Ag/AgCl,KClsat. Assays were run at room temperature and using sodium sulfate as supporting electrolyte. The samples collected during the tests were analyzed for chemical oxygen demand (COD), and for Total Organic Carbon (TOC) content. Analysis by UV-Visible absorption spectrophotometry was also performed. The best values of COD removals were 26% and 56% and the highest absorvance removals at 484 nm, were 11% and 94%, for the TiO2 platinized and not platinized anodes, respectively. TOC values remained almost unchanged throughout the tests.
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Keywords
Ao7. Corantes Azo Degradação Electroquímica Filmes Catalíticos Pulverização Catódica Dc Tio2