Síntese e caracterização de híbridos à base de alginato de sódio e escamas de peixe para uso na remoção de espécies poluentes

• Autor(a) principal: Cortes, Gracy Karla da Rocha
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/handle/riufs/3501
• topic: Escama de peixe; Alginato de sódio; Ecomateriais; Adsorção; Paraquat; Metais; Fish scales; Sodium alginate; Ecomaterials; Adsorption; Paraquat; Metals; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

With the purpose to develop environmentally appropriate materials, scales of the Piau fish and sodium alginate were used as precursor materials for the preparation of new ecomaterials which were used in the removal of the herbicide Paraquat and ions Co(II) and Cu(II). The hybrid material obtained from the reaction between the polysaccharide and scales was designated as ALG/ESC, and the hybrid ALG/ESC-CaCl2 was obtained from the crosslinking of the ALG/ESC with calcium chloride. The materials were characterized by FTIR, TG, SEM, XRD and determination of the point of zero charge (PZC). Changes in the peak observed in the FTIR spectrum of the ALG/ESC confirmed the existence of chemical interactions between Ca(II) of the hydroxyapatite present in fish scales, and the carboxylate groups of the sodium alginate. In the spectrum of ALG/ESC-CaCl2, bands were observed to be considerably narrower, due to crosslinking with the Ca(II) ions and tension of the carboxylate group that increases to accommodate the coordination structure around the Ca(II). It was observed an increase in sample thermal stability of the ALG/ESC-CaCl2 when compared to ALG/ESC, indicating the formation of the "egg box" structure. The SEM micrographs exhibited the presence of hydroxyapatite crystals on the surface of the ALG/ESC, and a homogeneous surface on the ALG/ESC-CaCl2 beads. Comparison between the X-ray diffraction profiles of the precursors (pure scales, ESC, and pure alginate, ALG) and those of the ALG/ESC and ALG/ESC-CaCl2 indicated that changes occurred due to incorporation of the hydroxyapatite structure in the alginate. From the PZC values of the materials, it was suggested that, in a general way, the interactions were controlled by electrostatic attractions between negatively charged surface groups and the cationic paraquat, or free Co(II) and Cu(II) ions, that are present in the solution, or between species of cobalt and copper in their anionic form and the surface groups that presented themselves as positively charged in the investigated pH range. From adsorption experiments carried out using the technique of batch with samples of solutions of the herbicide Paraquat and salts of copper and cobalt, the amount of adsorbed species per gram of adsorbent, Nf was determined. The values of Nf showed the highest affinity of the hybrid ALG/ESC-CaCl2 for the herbicide and the Co(II) and Co(II) ions. The adsorption rates were evaluated using the pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the data did present a good fit to the traditional intraparticle diffusion model. The data obtained from this model suggested that processes, other than simple intraparticle diffusion, may be occurring simultaneously.