Aplicação de processos oxidativos avançados na degradação de compostos fenólicos e de matéria orgânica em efluente vinícola
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Data
2022-02-15
Autores
Rodrigues, Ricardo Augusto
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Universidade Estadual Paulista (Unesp)
Resumo
Os compostos fenólicos naturais presentes em efluentes de indústrias vinícolas, como os ácidos fenólicos, estilbenos, flavonoides e taninos, apesar de benéficos para a saúde humana, são considerados recalcitrantes e tóxicos para organismos aquáticos, causando danos ambientais se lançados em corpos hídricos e capazes de diminuir a eficiência de tratamentos biológicos. Uma alternativa para tratar efluentes com tais compostos são os Processos Oxidativos Avançados (POAs), baseados na geração de radicais hidroxila, espécie química altamente oxidante, como a sonólise, a degradação de compostos por ondas de ultrassom que geram microbolhas que implodem com alta energia e que promovem a decomposição da molécula de água, produzindo os radicais hidroxila. A sonólise pode ser combinada com outros POAs como o processo de Fenton e de foto-Fenton e potencializar os efeitos desses processos. Assim, após a caracterização físico-química de um efluente líquido gerado por uma indústria vinícola da cidade de São Roque, Estado de São Paulo, Brasil, propôs-se uma investigação de metodologias de tratamento baseadas nos processos de Fenton e de foto-Fenton combinados com ondas de ultrassom, avaliando os efeitos individuais de cada componente e suas possíveis combinações na eficiência dos processos e determinando a redução de compostos fenólicos totais, demanda química de oxigênio, carbono orgânico total e cor. Com o processo de foto-Fenton foi possível reduzir 41,30% dos compostos fenólicos totais, 31,51% da demanda química de oxigênio, 13,92% do carbono orgânico total e 30,66% da cor, valores superiores aos atingidos pelo processo de Fenton devido à aplicação de radiação ultravioleta. Com a aplicação das ondas de ultrassom nos processos de sono-Fenton e de sono-foto-Fenton as reduções dos parâmetros analisados foram menores que as alcançadas pelos processos de Fenton e de foto-Fenton, comparados respectivamente, devido à ocorrência de outras reações que sequestram os radicais hidroxila gerados. Já a avaliação dos componentes de forma individual e em pares comprovou que a combinação entre os reagentes de Fenton, íons ferro (II) e peróxido de hidrogênio, são fundamentais para a maior produção de radicais hidroxila, devido às maiores reduções alcançadas quando estes dois componentes são adicionados. O tratamento de uma solução de ácido gálico, utilizado como composto modelo para compostos fenólicos também apresentou a mesma tendência na diminuição da concentração que os resultados para o efluente vinícola, comprovando que a matéria orgânica presente na matriz do efluente não é responsável pelas diminuições mais baixas dos parâmetros pelos processos com ultrassom, mas sim a interação entre as ondas ultrassônicas e o peróxido de hidrogênio, que diminui a quantidade de radicais hidroxila. Ao final dos tratamentos, o efluente não apresentou valores aceitáveis, dentro dos parâmetros utilizados no trabalho, para lançamento em corpos hídricos, mas os resultados obtidos indicam que o processo de Fenton e suas combinações são promissores no tratamento de efluentes agroindustriais que contenham compostos fenólicos naturais, inclusive como pré ou pós tratamento junto aos tratamentos biológicos convencionais.
Natural phenolic compounds present in wine industry wastewaters, such as phenolic acids, stilbenes, flavonoids and tannins, despite being beneficial to human health, are considered recalcitrant and toxic to aquatic organisms, causing environmental damage if released into water courses and capable of decreasing the efficiency of biological treatments. An alternative to treat wastewaters with such compounds is the Advanced Oxidation Processes (AOPs), based on the generation of hydroxyl radicals, a highly oxidizing species, such as sonolysis, the degradation of compounds by ultrasound waves that generate microbubbles that implode with high energy and that promote the degradation of the water molecule, producing hydroxyl radicals. Sonolysis can be combined with other POA's such as the Fenton and photo-Fenton processes and enhance the effects of these processes. Thus, after the physicochemical characterization of a liquid effluent generated by a wine industry in the city of São Roque, State of São Paulo, Brazil, an investigation of treatment methodologies based on the Fenton and photo-Fenton processes combined with ultrasound waves was proposed, evaluating the individual effects of each component and their possible combinations in the efficiency of the processes and determining the reduction of total phenolic compounds, chemical oxygen demand, total organic carbon and color. With the photo-Fenton process was possible to reduce 41.30% of total phenolic compounds, 31.51% of chemical oxygen demand, 13.92% of total organic carbon and 30.66% of color, these values were higher than those achieved by the Fenton process due to the application of ultraviolet radiation. With the application of ultrasound waves in the sono-Fenton and sono-photo-Fenton processes, the reductions of the analyzed parameters were lower than those achieved by the Fenton and photo-Fenton processes, compared respectively, due to the occurrence of reactions that scavenge the hydroxyl radicals. The evaluation of the components individually and in pairs proved that the combination of Fenton's reagents, ferrous iron and hydrogen peroxide, are essential for the greater production of hydroxyl radicals, due to the greater reductions achieved when these two components are added. The treatment of a gallic acid solution, used as a model compound for phenolic compounds, also showed the same trend in the decreasing of concentration, as the results for the winery wastewater, proving that the organic matter present in the effluent matrix is not responsible for the lower decreases of the parameters by the processes with ultrasound, but the interaction between the ultrasonic waves and hydrogen peroxide, which reduces the amount of hydroxyl radicals. At the end of the treatments, the wastewater did not present acceptable values, within the parameters used in this work, for release into water courses, but the results obtained indicate that the Fenton process and its combinations are promising in the treatment of agro-industrial effluents containing natural phenolic compounds, including as a pre or post treatment with conventional biological treatments.
Natural phenolic compounds present in wine industry wastewaters, such as phenolic acids, stilbenes, flavonoids and tannins, despite being beneficial to human health, are considered recalcitrant and toxic to aquatic organisms, causing environmental damage if released into water courses and capable of decreasing the efficiency of biological treatments. An alternative to treat wastewaters with such compounds is the Advanced Oxidation Processes (AOPs), based on the generation of hydroxyl radicals, a highly oxidizing species, such as sonolysis, the degradation of compounds by ultrasound waves that generate microbubbles that implode with high energy and that promote the degradation of the water molecule, producing hydroxyl radicals. Sonolysis can be combined with other POA's such as the Fenton and photo-Fenton processes and enhance the effects of these processes. Thus, after the physicochemical characterization of a liquid effluent generated by a wine industry in the city of São Roque, State of São Paulo, Brazil, an investigation of treatment methodologies based on the Fenton and photo-Fenton processes combined with ultrasound waves was proposed, evaluating the individual effects of each component and their possible combinations in the efficiency of the processes and determining the reduction of total phenolic compounds, chemical oxygen demand, total organic carbon and color. With the photo-Fenton process was possible to reduce 41.30% of total phenolic compounds, 31.51% of chemical oxygen demand, 13.92% of total organic carbon and 30.66% of color, these values were higher than those achieved by the Fenton process due to the application of ultraviolet radiation. With the application of ultrasound waves in the sono-Fenton and sono-photo-Fenton processes, the reductions of the analyzed parameters were lower than those achieved by the Fenton and photo-Fenton processes, compared respectively, due to the occurrence of reactions that scavenge the hydroxyl radicals. The evaluation of the components individually and in pairs proved that the combination of Fenton's reagents, ferrous iron and hydrogen peroxide, are essential for the greater production of hydroxyl radicals, due to the greater reductions achieved when these two components are added. The treatment of a gallic acid solution, used as a model compound for phenolic compounds, also showed the same trend in the decreasing of concentration, as the results for the winery wastewater, proving that the organic matter present in the effluent matrix is not responsible for the lower decreases of the parameters by the processes with ultrasound, but the interaction between the ultrasonic waves and hydrogen peroxide, which reduces the amount of hydroxyl radicals. At the end of the treatments, the wastewater did not present acceptable values, within the parameters used in this work, for release into water courses, but the results obtained indicate that the Fenton process and its combinations are promising in the treatment of agro-industrial effluents containing natural phenolic compounds, including as a pre or post treatment with conventional biological treatments.
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Qualidade Ambiental, Peroxidação, Ondas ultrassônicas Aplicações industriais, Águas residuais Purificação, Environmental quality, Peroxidation, Ultrasonic waves Industrial applications