Produção e caracterização de nanocompósitos PVDF/argila e PVDF/zeólita obtidos pela técnica de fiação por sopro em solução para remoção de metais
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Data
2017-06-02
Autores
Zadorosny, Lincon [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Nanocompósitos com matriz de fibras em escala micro e nanométrica de poli(fluoreto de vinilideno) – PVDF com adição de argila montmorilonita ou zeólita faujasita – FAU, nas concentrações de 3%, 5%, 10%, 20% e 30%, foram produzidas pela técnica de fiação por sopro em solução e submetidas a caracterizações morfológica e estrutural (Microscopia Eletrônica de Varredura – MEV, Difratometria de Raios X – DRX e Energia Dispersiva de Raios X – EDX). As análises térmicas foram feitas por Calorimetria Exploratória Diferencial – DSC e Análise Termogravimétrica – TGA; as mecânicas por análises de Tensão – Deformação; e de molhabilidade por Ângulo de Contato. As amostras foram submetidas a testes de remoção de metais pesados através da adsorção em banho e em membrana. Os resultados demonstraram queda da espessura dos nanocompósitos, que passaram de 500 μm do polímero puro, para 251 μm e 315 μm para os nanocompósitos com 30% de argila e FAU, respectivamente. A técnica de MEV evidenciou amostras com grande quantidade de fibras lisas, uniformes, cilíndricas e pouco aglomeradas, cujos diâmetros foram inferiores a 200 nm. A ferramenta de EDX confirmou a presença dos elementos da argila e da FAU dispersos por todo o filme, porém surgem aglomerados com o aumento de sua concentração. A técnica de DRX demonstrou a presença das fases cristalinas α e β da matriz, além disso, o aumento da quantidade de argila e FAU nos nanocompósitos intensificou seus picos característicos. A técnica DSC revelou que o ponto de fusão não foi alterado, porém o TGA indica que as cargas atuam como catalisadores, diminuindo a temperatura de degradação. Os testes de tensão-deformação apontaram queda na deformação dos nanocompósitos, no entanto, a tensão na ruptura e módulo de elasticidade apresentam melhora com a incorporação de até 5% de cargas. O ângulo de contato demonstrou que a presença das cargas nos filmes aumenta a rugosidade da superfície elevando sua hidrofobicidade, mas a adição de 5% de etanol a água aumentou a molhabilidade dos mesmo. Os testes de adsorção (banho) mostraram que os nanocompósitos com 30% no tempo de 24 horas em meio água/etanol (95/5 V/V), foram condições ideais, atingindo 87% de remoção de Pb. Os modelos de pseudo-segunda ordem e Langmuir foram os mais apropriados para descrever os dados cinéticos e de isoterma de adsorção, respectivamente. Os testes de membrana apontaram os nanocompósitos com 10%, tanto de argila quanto de FAU os mais indicados, atingindo remoção superior a 90% dos metais, sendo a presença do etanol um parâmetro menos relevante.
Nanocomposites with fibers matrix at micron and nanoscale of poly(vinylidene fluoride) - PVDF with addition of montmorillonite clay or faujasite zeolite - FAU, in the concentrations of 3%, 5%, 10%, 20% and 30% were produced by the solution blow spinning technique and submitted to morphological and structural characterizations, i.e., Scanning Electron Microscopy–SEM, X-ray Diffractometry-XRD and X-ray Dispersive Energy-EDX. The thermal analyzes were made by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The mechanics characterizations were carried out by stress-strain analysis and wettability characteristics was analyzed by Contact Angle. The samples were subjected to tests of heavy metal removal by adsorption on a bath and on a membrane. The results showed a decreasing of the thickness of the nanocomposites, from 500 μm for the pure polymer to 251 μm and 315 μm for the nanocomposites with 30% of clay and FAU, respectively. SEM technique showed samples with a large amount of smooth, uniform, cylindrical and slightly agglomerated fibers whose diameters were lower than 200 nm. The EDX tool confirmed the presence of the elements of the clay and FAU dispersed through the film. However, agglomerates appear as the concentration of those materials is increased. The XRD technique showed the presence of the crystalline phases α and β of the matrix, in addition, the increase of the amount of clay and FAU in the nanocomposites intensified its characteristic peaks. The DSC technique showed that the melting point was not altered, but the TGA indicates that the charges act as catalysts, reducing the degradation temperature. The stress-strain tests showed a decrease in the deformation of the nanocomposites, however, the tensile strength at the rupture and modulus of elasticity showed improvement with the incorporation of up to 5% of charges. The contact angle showed that the presence of the fillers in the films increases surface roughness by increasing their hydrophobicity, but the addition of 5% of ethanol in the water increased the surface wettability. The adsorption tests showed that the ideal conditions for the higher removal content of led (87%) was using nanocomposites in concentration of 30% during 24 hours in water/ethanol (95/5 V/V). The pseudo-second order and Langmuir models were the most appropriate to describe the kinetic and the adsorption isotherm data, respectively. Membrane tests indicated that the nanocomposites with 10% of both clay and FAU were the most indicated, achieving a removal content of more than 90% of the metals. Additionally, the presence of ethanol was not relevant.
Nanocomposites with fibers matrix at micron and nanoscale of poly(vinylidene fluoride) - PVDF with addition of montmorillonite clay or faujasite zeolite - FAU, in the concentrations of 3%, 5%, 10%, 20% and 30% were produced by the solution blow spinning technique and submitted to morphological and structural characterizations, i.e., Scanning Electron Microscopy–SEM, X-ray Diffractometry-XRD and X-ray Dispersive Energy-EDX. The thermal analyzes were made by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The mechanics characterizations were carried out by stress-strain analysis and wettability characteristics was analyzed by Contact Angle. The samples were subjected to tests of heavy metal removal by adsorption on a bath and on a membrane. The results showed a decreasing of the thickness of the nanocomposites, from 500 μm for the pure polymer to 251 μm and 315 μm for the nanocomposites with 30% of clay and FAU, respectively. SEM technique showed samples with a large amount of smooth, uniform, cylindrical and slightly agglomerated fibers whose diameters were lower than 200 nm. The EDX tool confirmed the presence of the elements of the clay and FAU dispersed through the film. However, agglomerates appear as the concentration of those materials is increased. The XRD technique showed the presence of the crystalline phases α and β of the matrix, in addition, the increase of the amount of clay and FAU in the nanocomposites intensified its characteristic peaks. The DSC technique showed that the melting point was not altered, but the TGA indicates that the charges act as catalysts, reducing the degradation temperature. The stress-strain tests showed a decrease in the deformation of the nanocomposites, however, the tensile strength at the rupture and modulus of elasticity showed improvement with the incorporation of up to 5% of charges. The contact angle showed that the presence of the fillers in the films increases surface roughness by increasing their hydrophobicity, but the addition of 5% of ethanol in the water increased the surface wettability. The adsorption tests showed that the ideal conditions for the higher removal content of led (87%) was using nanocomposites in concentration of 30% during 24 hours in water/ethanol (95/5 V/V). The pseudo-second order and Langmuir models were the most appropriate to describe the kinetic and the adsorption isotherm data, respectively. Membrane tests indicated that the nanocomposites with 10% of both clay and FAU were the most indicated, achieving a removal content of more than 90% of the metals. Additionally, the presence of ethanol was not relevant.
Descrição
Palavras-chave
Nanocompósito, PVDF, Argila, FAU, FSS, remoção de metais., FSS, Remoção de metais, Nanocomposite, PVDF, Clay, SBS, Metal removal