Caracteriza??o e aplica??o de vermicultura natural e quimicamente modificada na adsor??o de azul de metileno

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Chemical modification of clays has been extremely studied in the search for improvements of their properties for use in various areas, such as in combating pollution by industrial effluents and dyes. In this work, the vermiculite was chemically modified in two ways, characterized and evaluated the adsorption of methylene blue dye. First was changed with the addition of a surfactant (hexadecyltrimethylammonium bromide, BHTA) making it an organophilic clay and then by adding an acid (HCl) by acid activation. Some analyzes were performed as X-ray fluorescence (FRX), X-ray diffraction (DRX), adsorption isotherms of methylene blue dye, infrared (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis and spectroscopy energy dispersive (EDS). Analysis by FRX of natural vermiculite indicates that addition of silicon and aluminum, clay presents in its structure the magnesium, calcium and potassium with 16 % organic matter cations. The DRX analyzes indicated that the organic vermiculite was an insertion of the surfactant in the space between the lamellae, vermiculite and acid partial destruction of the structure with loss of crystallinity. The adsorption isotherms of methylene blue showed that there was a significant improvement in the removal of dye to the vermiculite with the addition of cationic surfactant hexadecyltrimethylammonium bromide and treatment with acid using HCl 2 mol/L. In acid vermiculites subsequently treated with surfactant, the adsorption capacity increased with respect to natural vermiculite, however was much lower compared vermiculite modified with acid and surfactant separately. Only the acidic vermiculite treated with surfactant adjusted to the Langmuir model. As in the infrared spectrometry proved the characteristics of natural vermiculite. In the organic vermiculite was observed the appearance of characteristic bands of CH3, CH2, and (CH3)4N. Already on acid vermiculite, it was realized a partial destruction with decreasing intensity of the characteristic band of vermiculite that is between 1074 and 952 cm-1. In the SEM analysis, it was observed that there was partial destruction to the acid treatment and a cluster is noted between the blades caused by the presence of the surfactant. The TG shows that the higher mass loss occurs at the beginning of the heating caused by the elimination of water absorbed on the surface between layers. In the organic vermiculite also observed a loss of mass between 150 and 300 ?C caused decomposition of the alkylammonium molecules (surfactants)

A modifica??o qu?mica de argilas tem sido extremamente estudada na busca por melhorias de suas propriedades para seu uso em diversas ?reas, como por exemplo, no combate a polui??o ocasionada por efluentes industriais como corantes. Neste trabalho, a vermiculita foi modificada quimicamente de duas maneiras, caracterizada e avaliada na adsor??o do corante azul de metileno. Primeiro foi alterada com adi??o de um surfactante (brometo de hexadeciltrimetilam?nio, BHTA) tornando-a uma argila organof?lica e depois pela adi??o de um ?cido (HCl) por ativa??o ?cida. Algumas an?lises foram realizadas como fluoresc?ncia de raios-X (FRX), difra??o de raios-X (DRX), isotermas de adsor??o do corante azul de metileno, infravermelho (FTIR), microscopia eletr?nica de varredura (MEV), an?lise termogravim?trica e Espectroscopia de energia dispersiva (EDS). An?lise por FRX da vermiculita natural indica que al?m do sil?cio e do alum?nio, a argila apresenta em sua estrutura os c?tions magn?sio, c?lcio e pot?ssio com 16 % de mat?ria org?nica. As an?lises por DRX indicam que na vermiculita org?nica houve uma inser??o do surfactante no espa?o entre as lamelas, e na vermiculita ?cida uma destrui??o parcial da estrutura com perda de cristalinidade. As isotermas de adsor??o do azul de metileno mostraram que houve uma melhora significativa na remo??o do corante para a vermiculita com a adi??o do surfactante cati?nico brometo de hexadeciltrimetilam?nio, bem como com tratamento ?cido utilizando HCl 2 mol/L. Nas vermiculitas ?cidas tratadas posteriormente com o surfactante, a capacidade de adsor??o aumentou em rela??o a vermiculita natural, porem foi bem menor em rela??o as vermiculitas modificadas com o ?cido e com o surfactante separadamente. S? as vermiculitas ?cidas tratadas com surfactante se ajustaram ao modelo de Langmuir. A espectrometria na regi?o do infravermelho comprovou as caracter?sticas da vermiculita natural. Na vermiculita org?nica observou-se o aparecimento de bandas caracter?sticas de grupos CH3, CH2, al?m de (CH3)4N. J? na vermiculita ?cida, percebeu-se uma destrui??o parcial com a diminui??o de intensidade da banda caracter?stica das vermiculitas que ? entre 1074 e 952 cm-1. Na an?lise de MEV, observou-se que houve destrui??o parcial com no tratamento ?cido e nota-se um aglomerado entre as l?minas causado pela presen?a do surfactante. As curvas TG mostram que a maior perda de massa ocorre no come?o do aquecimento ocasionado pela elimina??o de ?gua absorvida na superf?cie entre camadas. Na vermiculita org?nica tamb?m observa uma perda de massa entre 150 e 300 ?C ocasionada pela decomposi??o das mol?culas de alquilam?nio (surfactante)