Estudo da adsorção de herbicida ácido 2,4-diclorofenoxiacético em processo contínuo e descontínuo utilizando-se de carvão ativo granular
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Data
2021-03-25
Autores
Raszl, Regina Célia Modesto
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Universidade Estadual Paulista (Unesp)
Resumo
A preocupação com a contaminação dos corpos hídricos por agroquímicos, vem crescendo nos últimos anos com o aumento significativo, do uso dessas substâncias no Brasil. Como os agroquímicos não são, efetivamente, removidos no tratamento convencional da água, processos mais complexos para sua remoção são necessários, para garantir uma água potável livre desses poluentes. O herbicida, ácido 2,4-diclorofenoxiacético (2,4-D) é um dos defensivos agrícolas mais comercializados, para controlar diversas espécies de plantas e, uma vez que este contamina os corpos hídricos, faz-se necessário o emprego de técnicas alternativas, que removam este poluente da água, já que as técnicas convencionais de tratamento são incapazes de removê-lo. A adsorção por carvão ativo é um método eficaz e amplamente utilizado, na remoção de poluentes tanto da água para consumo humano como de efluentes. O objetivo do presente trabalho volta-se para o estudo de eficiência na remoção do 2,4-D da água dopada, com carvão ativo e a comparação com a capacidade de adsorção da zeólita natural comercial. No processo descontínuo (batelada) foram avaliados os parâmetros de pH da solução, concentração de adsorvente e concentração inicial de poluente, a fim de verificar as variáveis mais adequadas. Após adsorção, as amostras foram filtradas em membrana de 0,45 μm e a detecção do 2,4-D residual efetuada por cromatografia líquida de alta eficiência (CLAE). Os resultados obtidos foram em torno de 97,3% de remoção do poluente pelo carvão ativo e a capacidade máxima de adsorção encontrada pela isoterma de Langmuir aplicando-se o algoritmo de Marquadt-Levenberg (mínimos quadrados) foi de aproximadamente 88 mg g-1. Já a zeólita analisada teve baixa eficiência de remoção (em torno de 5%). No processo contínuo (leito fixo), a capacidade de adsorção do carvão ativo foi de 34,5 mg g-1 e os modelos matemáticos utilizados tiveram um bom ajuste dos dados, com desvio em torno de 5,5 % entre os dados experimentais e teóricos, comprovando que os dados obtidos podem ser utilizados para projetar uma coluna de leito fixo de grande escala. A técnica de adsorção pelo carvão ativo, demonstrou ser uma alternativa eficiente de remoção deste poluente da água para consumo humano e de efluentes. O processo de adsorção apresenta características promissoras, sob o aspecto econômico e de eficiência de remoção.
The concern with the contamination of water bodies by agrochemicals has been growing in recent years with the significant increase in the use of these substances in Brazil. As the agro-chemicals are not effectively removed in conventional water treatment, more complex pro-cesses for their removal are necessary to guarantee drinking water free of these pollutants. The herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), is one of the most commercialized pesti-cides to control several species of plants and, since it contaminates water bodies, it is neces-sary to use alternative techniques to remove this pollutant from the water, since conventional treatment techniques are unable to remove it. The adsorption by activated carbon is an effi-cient and widely used method to remove pollutants from drinking water and effluents. The objective of the present work is to study the efficiency of 2,4-D removal from doped water with activated carbon and to compare it with the adsorption capacity of commercial natural zeolite. In the batch process, the parameters of solution pH, adsorbent concentration and ini-tial pollutant concentration were evaluated in order to verify the most appropriate variables. After adsorption, the samples were filtered through a 0.45 μm membrane and the residual 2,4-D was detected by high performance liquid chromatography (HPLC). The results obtained were around 97.3% removal of the pollutant by activated carbon and the maximum adsorption capacity found by the Langmuir isotherm applying the Marquadt-Levenberg algorithm (least squares) was approximately 88 mg g-1. The zeolite analyzed had a low removal efficiency (around 5%). In the continuous process (fixed bed), the adsorption capacity of the activated carbon was 34.5 mg g-1 and the mathematical models used had a good data fit, with deviation around 5.5% between experimental and theoretical data, proving that the data obtained can be used to design a large scale fixed bed column. The adsorption technique by activated carbon, proved to be an efficient alternative for removal of this pollutant from drinking water and effluents. The adsorption process presents promising characteristics, under the economical aspect and of removal efficiency.
The concern with the contamination of water bodies by agrochemicals has been growing in recent years with the significant increase in the use of these substances in Brazil. As the agro-chemicals are not effectively removed in conventional water treatment, more complex pro-cesses for their removal are necessary to guarantee drinking water free of these pollutants. The herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), is one of the most commercialized pesti-cides to control several species of plants and, since it contaminates water bodies, it is neces-sary to use alternative techniques to remove this pollutant from the water, since conventional treatment techniques are unable to remove it. The adsorption by activated carbon is an effi-cient and widely used method to remove pollutants from drinking water and effluents. The objective of the present work is to study the efficiency of 2,4-D removal from doped water with activated carbon and to compare it with the adsorption capacity of commercial natural zeolite. In the batch process, the parameters of solution pH, adsorbent concentration and ini-tial pollutant concentration were evaluated in order to verify the most appropriate variables. After adsorption, the samples were filtered through a 0.45 μm membrane and the residual 2,4-D was detected by high performance liquid chromatography (HPLC). The results obtained were around 97.3% removal of the pollutant by activated carbon and the maximum adsorption capacity found by the Langmuir isotherm applying the Marquadt-Levenberg algorithm (least squares) was approximately 88 mg g-1. The zeolite analyzed had a low removal efficiency (around 5%). In the continuous process (fixed bed), the adsorption capacity of the activated carbon was 34.5 mg g-1 and the mathematical models used had a good data fit, with deviation around 5.5% between experimental and theoretical data, proving that the data obtained can be used to design a large scale fixed bed column. The adsorption technique by activated carbon, proved to be an efficient alternative for removal of this pollutant from drinking water and effluents. The adsorption process presents promising characteristics, under the economical aspect and of removal efficiency.
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Palavras-chave
Herbicida, 2.4-D, Adsorção, Carvão ativo, Remoção de contaminante, Herbicides, Activated carbon