Síntese e caracterização de carvões ativados magnéticos (CAMs) da casca do coco (Cocos nucifera) : estudos de adsorção do corante amarelo crepúsculo

• Autor(a) principal: Cazetta, André Luiz
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/4719
• topic: Carvão ativado magnético - Casca do coco; Carvão ativado magnético - Casca do coco; Adsorsão - Corante; Ciências Exatas e da Terra; Química

Magnetic activated carbons (MACs) are carbonaceous materials that exhibit low cost and toxicity, when applied in adsorption processes can be easily removed or separated using a magnetic external field. In the present work, the MACs were synthesized using the coconut shell (Cocos nucifera) carbonized (Cb) and ferric chloride (FeCl3.6H2O) through the simultaneous process of activation and impregnation. The synthesis of MACs were performed in impregnations ratio (FeCl3.6H2O:Cb) of 1:1, 2:1 and 3:1 (wt:wt), the obtained materials were denoted as MAC1, MAC2 e MAC3 respectively. Textural characterization showed that the MACs were essentially microporous, and that microporosity increases with the increase of the impregnation ratio. Additionally, BET surface area values (SBET) were 372, 337 and 238 m2 g-1 for the MAC1, MAC2 and MAC3, respectively. Elementary analysis by XPS shown that the MACs are constituted mostly by carbon and oxygen, the analysis of the deconvoluted spectras indicated the presence of magnetite (Fe3O4), maghemite (?-Fe2O3) and hematite (?-Fe2O3). X-Ray pattern confirmed the presence of hematite and magnetite with high degree of crystallinity. The analysis of the hyperfine parameters of Mössbauer spectra showed the presence of maghemite in phase mixture with magnetite, in addition, was possible to identify the presence of nanoparticles of hematite in superparamagnetic state. SEM images showed that the increase of impregnation ratio causes a reduction on the surface cracks of the MACs. pHpzc values showed that the materials have acidic characteristics and that the acidity increases with the increase of impregnation ratio. The adsorption studies of the food dye Sunset Yellow onto MAC1 showed that the Elovich model was satisfactory to describe the experimental data in low initial concentration; however, with the increasing of the concentration, the pseudo-second order model was best fitted. Equilibrium studies of adsorption indicated that the Langmuir model is more adequate to describe the process, presenting a monolayer adsorption capacity of 22.3 mg g-1. The Dubinin-Radushkevich model showed that the chemisorption contributes significantly in the adsorption process