Obtenção e caracterização de esferas de PVDF/argila para a remoção de íons metálicos
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Data
2019-04-12
Autores
Cardoso, Mayk Ferreira
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Universidade Estadual Paulista (Unesp)
Resumo
A contaminação do meio ambiente por metais potencialmente tóxicos constitui-se de um sério problema que altera ecossistemas e tem impacto direto na saúde da população. Desta forma, o desenvolvimento de novos materiais capazes de remover estes metais é sem dúvida essencial e muito importante. Neste trabalho, foram obtidas esferas de PVDF/argila pelo método de gotejamento. Imagens de MEV indicam haver uma fina camada pouco porosa e hidrofóbica envolvendo as esferas. Internamente há a presença de estrutura porosa. Os ensaios de adsorção foram realizados em água e em mistura água/etanol (95/5), contendo 5 mg/L de cobre. O teste para a determinação do ponto de carga zero (pHPCZ), que indica o pH ideal da solução onde a adsorção do metal pelo material é mais efetiva, foi determinado como sendo de 6,4 e 5,9, para os meios aquoso e etanólico, respectivamente. Ensaios de adsorção por batelada indicaram a concentração de 30% de argila em relação à massa de PVDF como sendo a mais efetiva entre as testadas com remoção de 32,4% e 46,8% do total de cobre presente para os meios aquoso e etanólico, respectivamente. Ensaios de isotermas de adsorção apontam que os dados se ajustam melhor ao modelo BET. Foram encontradas capacidades máximas de adsorção de 0,361 e 0,734 mg Cu/g para os meios aquoso e etanólico, respectivamente. Capacidades de adsorção relativamente baixas podem estar relacionadas à camada externa pouco porosa do material e à hidrofobicidade do PVDF. A adsorção de cobre de cachaça em colunas contendo esferas cortadas resultaram em índices de adsorção acima de 50% para amostras de variadas concentrações de cobre. Tais índices de remoção enquadraram as amostras dentro da legislação vigente.
Contamination of the environment by heavy metals is a serious problem that alters ecosystems and has a direct impact on the health of the population. In this way, the development of new materials capable of removing these metals is undoubtedly essential and very important. In this work, PVDF / clay beads were obtained by the drip method. SEM images indicated porous internal structure, but surrounded by a layer with few pores. The adsorption tests were performed in water and in water/ethanol (95/5) containing 5 mg/L of copper. The test for determination of the point of zero charge (PZC), which indicates the solution pH where the adsorption of the metal by the material is more effective, was determined to be 6.4 and 5.9 for the aqueous and ethanoic media, respectively. Batch adsorption assays indicated the concentration of 30% clay in relation to the PVDF mass as the most effective among those tested with removal of 32.4% and 46.8% of the total copper present for the aqueous and ethanoic media, respectively. Adsorption isotherms tests indicate the BET model as the one that best describes the data. Maximum adsorption capacities of 0.361 and 0.734 mg Cu / g were found for the aqueous and ethanoic media, respectively. Relative low adsorption capacities may be related to the slightly porous outer layer of the material and the hydrophobicity of PVDF. The adsorption of copper from cachaça in columns containing cut spheres resulted in adsorption indices above 50% for samples of various concentrations of copper. Such removal indices fit the samples within the current legislation.
Contamination of the environment by heavy metals is a serious problem that alters ecosystems and has a direct impact on the health of the population. In this way, the development of new materials capable of removing these metals is undoubtedly essential and very important. In this work, PVDF / clay beads were obtained by the drip method. SEM images indicated porous internal structure, but surrounded by a layer with few pores. The adsorption tests were performed in water and in water/ethanol (95/5) containing 5 mg/L of copper. The test for determination of the point of zero charge (PZC), which indicates the solution pH where the adsorption of the metal by the material is more effective, was determined to be 6.4 and 5.9 for the aqueous and ethanoic media, respectively. Batch adsorption assays indicated the concentration of 30% clay in relation to the PVDF mass as the most effective among those tested with removal of 32.4% and 46.8% of the total copper present for the aqueous and ethanoic media, respectively. Adsorption isotherms tests indicate the BET model as the one that best describes the data. Maximum adsorption capacities of 0.361 and 0.734 mg Cu / g were found for the aqueous and ethanoic media, respectively. Relative low adsorption capacities may be related to the slightly porous outer layer of the material and the hydrophobicity of PVDF. The adsorption of copper from cachaça in columns containing cut spheres resulted in adsorption indices above 50% for samples of various concentrations of copper. Such removal indices fit the samples within the current legislation.
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Palavras-chave
Adsorvente, Compósito, Cobre, Adsorptive, Composite, Copper