Aplicação de processos de oxidação química, utilizando um catalisador heterogéneo com base na esmectite, conjugados com radiação
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2018-01-12
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A água é o recurso natural mais utilizado pelo ser humano sendo usada para várias atividades do dia-a-dia. Ao longo dos anos cada vez mais a qualidade de água é afetada por substâncias químicas dissolvidas e também por elevada carga orgânica, como é o caso dos efluentes vinícolas sendo prejudiciais principalmente para cursos de água naturais, tornando-se fundamental o seu tratamento antes de serem libertados para o meio ambiente.
Este trabalho tem como objetivo contribuir para o desenvolvimento e otimização dos processos de tratamento de efluentes vinícolas. Neste sentido, foi desenvolvido um catalisador heterogéneo com base num mineral argiloso, a esmectite, que, posteriormente, foi utilizado em Processos de Oxidação Avançados (POA): os processos Fenton e foto-Fenton. Na aplicação prática destes sistemas oxidantes utilizou-se como estudo de caso um efluente vinícola da região de Trás-os-Montes e Alto Douro, que é uma das maiores regiões produtoras de vinho em Portugal. A eficiência destes tratamentos foi avaliada principalmente através da mineralização da matéria orgânica (Carbono Orgânico Total – COT). No processo foto-Fenton, a fonte de radiação utilizada foi um sistema de LEDs de 70 W/m2.
A primeira fase deste trabalho consistiu num estudo da capacidade de adsorção da esmectite de modo a otimizar os parâmetros experimentais que permitiam melhores resultados de adsorção de matéria orgânica do efluente vinícola, variando três parâmetros importantes para o processo: valor de pH, razão entre a massa de adsorvente e volume de solução (S:L) e a concentração inicial de matéria orgânica. As experiências realizadas a diferentes valores de pH inicial permitiram concluir que para a Ca-SMT o valor de pH mais favorável ao processo de adsorção é 3,6 (qe=39,5 mg/g), e para a Fe-SMT é 5,0 (qe≈30 mg/g). Quando se efetuou a variação da razão S:L foi possível verificar que, para ambas as esmectites, a razão S:L que apresenta uma maior quantidade de matéria orgânica adsorvida no equilíbrio é 1,5 gSMT/L, sendo esta de 84,1 mg/g (Ca-SMT) e 47,1 mg/g (Fe-SMT). A análise dos resultados experimentais obtidos pelas experiências realizadas com diferentes concentrações iniciais de matéria orgânica do efluente vinícola, revelou que a maior quantidade de matéria orgânica adsorvida na esmectite ocorre quando há uma maior presença desta no efluente, tendo-se alcançado uma adsorção máxima de matéria orgânica de 177,8 mg/g e 137,2 mg/g para a Ca-SMT e Fe-SMT, respetivamente, quando as concentrações iniciais de matéria orgânica foram 1180 mg C/L (Ca-SMT) e 990 mg C/L (Fe-SMT).
Aplicação de processos de oxidação química, utilizando um catalisador heterogéneo com base na
esmectite, conjugados com radiação UV/LEDs a efluentes vinícolas
xii
Numa segunda fase, foram realizadas reações Fenton onde o melhor resultado de remoção de COT (27,5%) foi obtido utilizando 1,5 g de Fe-SMT e 5,0 mL de H2O2 adicionados no início da reação.
Na terceira fase deste trabalho, envolvendo o processo foto-Fenton, alcançou-se uma remoção de COT de 94,4% e de CQO de 96,5%, quando utilizadas 1,5 g de Fe-SMT e 10,0 mL de H2O2 adicionados em frações.
Os resultados obtidos permitem concluir que entre os dois Processos de Oxidação Avançados (POA) estudados neste trabalho, o que constitui uma alternativa mais promissora para o tratamento de efluentes vinícolas é o processo foto-Fenton.
The water is the natural resource most used by humans being used daily for multiples activities. Over the years the water quality is increasingly affected by dissolved chemicals and also by high organic load, as is the case of the wine effluents, being harmful mainly to natural water courses, making it essential to treat them before being released into the environment. This work aims to contribute to the development and optimization of the processes of treatment of wine effluents. In this sense, a heterogeneous catalyst was developed based on clay minerals, the smectite, which was later used in Advanced Oxidation Processes (AOP): the Fenton and photo-Fenton processes. In the practical application of these oxidizing systems a wine effluent from the Trás-os-Montes e Alto Douro region, which is one of the largest wine producing regions in Portugal, was used as a case study. The efficiency of these treatment processes was evaluated through the moralization of organic matter (Total Organic Carbon-TOC). In the photo-Fenton process, the radiation source used was a 70 W/m2 LED system. The first phase of this work consisted in a study of the adsorption capacity of the smectite in order to optimize the experimental parameters that allowed better results of adsorption of organic matter of the wine effluent, varying three important parameters for the adsorption process: pH value, ratio between the mass of adsorbent and volume of solution (S:L) and the initial concentration of organic matter. The experiments carried out at different initial pH values allowed us to conclude that for Ca-SMT the pH value most favorable to the process is 3.6 (qe=39.5 mg/g) and for Fe-SMT it is 5.0 (qe≈30 mg/g). When the S:L ratio was changed, it was possible to verify that, for both smectites, the S:L ratio with the highest amount of organic matter adsorbed at equilibrium is 1.5 gSMT/L, which is 84.1 mg/g (Ca-SMT) e 47.1 mg/g (Fe-SMT). The analysis of the experimental results obtained by the experiments carried out with different initial concentrations of organic matter of the wine effluent revealed that the highest amount of organic matter adsorbed in the smectite occurs when there is a greater presence of this in the effluent, having reached a maximum adsorption of organic matter of 177.8 mg/g and 137.2 mg/g for Ca-SMT and Fe-SMT, respectively, when the initial concentrations of organic matter were 1180 mg C/L (Ca-SMT) and 990 mg C/L (Fe-SMT). In a second phase, Fenton reactions were performed where the best TOC removal result (27.5%) was obtained using 1.5 g of Fe-SMT and 5.0 mL of H2O2 added at the beginning of the reaction. Aplicação de processos de oxidação química, utilizando um catalisador heterogéneo com base na esmectite, conjugados com radiação UV/LEDs a efluentes vinícolas xiv In the third phase of this work, involving the photo-Fenton reaction, a COT removal of 94.4% and COD of 96.5% was achieved, when 1.5 g of Fe-SMT and 10.0 mL of H2O2 added in fractions. The results obtained allow us to conclude that between the two processes of Advanced Oxidation (POA) studied in this work, the process which constitutes a more promising alternative for the treatment of wine effluents is the photo-Fenton process.
The water is the natural resource most used by humans being used daily for multiples activities. Over the years the water quality is increasingly affected by dissolved chemicals and also by high organic load, as is the case of the wine effluents, being harmful mainly to natural water courses, making it essential to treat them before being released into the environment. This work aims to contribute to the development and optimization of the processes of treatment of wine effluents. In this sense, a heterogeneous catalyst was developed based on clay minerals, the smectite, which was later used in Advanced Oxidation Processes (AOP): the Fenton and photo-Fenton processes. In the practical application of these oxidizing systems a wine effluent from the Trás-os-Montes e Alto Douro region, which is one of the largest wine producing regions in Portugal, was used as a case study. The efficiency of these treatment processes was evaluated through the moralization of organic matter (Total Organic Carbon-TOC). In the photo-Fenton process, the radiation source used was a 70 W/m2 LED system. The first phase of this work consisted in a study of the adsorption capacity of the smectite in order to optimize the experimental parameters that allowed better results of adsorption of organic matter of the wine effluent, varying three important parameters for the adsorption process: pH value, ratio between the mass of adsorbent and volume of solution (S:L) and the initial concentration of organic matter. The experiments carried out at different initial pH values allowed us to conclude that for Ca-SMT the pH value most favorable to the process is 3.6 (qe=39.5 mg/g) and for Fe-SMT it is 5.0 (qe≈30 mg/g). When the S:L ratio was changed, it was possible to verify that, for both smectites, the S:L ratio with the highest amount of organic matter adsorbed at equilibrium is 1.5 gSMT/L, which is 84.1 mg/g (Ca-SMT) e 47.1 mg/g (Fe-SMT). The analysis of the experimental results obtained by the experiments carried out with different initial concentrations of organic matter of the wine effluent revealed that the highest amount of organic matter adsorbed in the smectite occurs when there is a greater presence of this in the effluent, having reached a maximum adsorption of organic matter of 177.8 mg/g and 137.2 mg/g for Ca-SMT and Fe-SMT, respectively, when the initial concentrations of organic matter were 1180 mg C/L (Ca-SMT) and 990 mg C/L (Fe-SMT). In a second phase, Fenton reactions were performed where the best TOC removal result (27.5%) was obtained using 1.5 g of Fe-SMT and 5.0 mL of H2O2 added at the beginning of the reaction. Aplicação de processos de oxidação química, utilizando um catalisador heterogéneo com base na esmectite, conjugados com radiação UV/LEDs a efluentes vinícolas xiv In the third phase of this work, involving the photo-Fenton reaction, a COT removal of 94.4% and COD of 96.5% was achieved, when 1.5 g of Fe-SMT and 10.0 mL of H2O2 added in fractions. The results obtained allow us to conclude that between the two processes of Advanced Oxidation (POA) studied in this work, the process which constitutes a more promising alternative for the treatment of wine effluents is the photo-Fenton process.
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Efluentes vinícolas , Processos de Oxidação Avançados , minerais argilosos , absorção , reação Fenton , foto-Fenton