Síntese de alfa-alumina nanoestruturada não dopada e dopada com cromo a partir da matéria orgânica natural e resíduos da indústria de curtume

• Ano de defesa: 2014
• Autor(a) principal: Cunha, Graziele da Costa
• Orientador(a): Macedo, Zélia Soares
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Sergipe
• Programa de Pós-Graduação: Pós-Graduação em Ciência e Engenharia de Materiais
• País: BR
• Palavras-chave em Português: Alfa-alumina; MON; Reciclagem; Nanopigmento cerâmico; Materiais; Couros; Materiais nanoestruturados; Reaproveitamento (Sobras, refugos, etc.); Cromo; Óxido de alumínio; Luminescência
• Palavras-chave em Inglês: Alpha-alumina; Recycle; Chromium; Ceramic pigment
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: https://ri.ufs.br/handle/riufs/3474

Alumina nanoparticles are among the most important materials in the ceramic industry due to their variety of potential applications. Currently, there is a search for more economic, eco friendly and efficient routes. In this way, the present work proposes the use of complexing capacity of water rich in Natural Organic Matter (NOM) (24mg L -1 COD) to synthesize nanostructured pigment, based on doped alumina with chrome ions obtained from reagents with high degree of purity of from solid and liquid residues from the tannery industry. In the synthesis process, many parameters were controlled, such as the pH of the precursor solution. It was observed that this parameter played a significant role on the production of particles with small sizes. Using pH 4,0 undoped alfa-alumina was obtained after calcination at 1000ºC/4h. This temperature is at least 200ºC lower than those reported for the production of alumina using sol-gel or Pechini routes. For doped alumina, the calcination conditions were 1100°C/4h, showing that doping had an influence over the phase transition temperature. The XRF data revealed that Cl, Si, Zn, S and Cu are the main impurities in the pure sample, as well as in the sample doped with chrome salts with high purity. On the other hand, the samples doped with recycled chrome contained compounds of calcium and sodium chloride, depending on the type of residue used (solid or liquid). Data from XANES proved that the valence of Cr in the alumina structure is influenced by the degree of purity of the dopant. Micrographs suggest the obtention of structures with spherical morphology, with particle sizes varying from 45 nm to 56 nm, showing that the origin of NOM, its molecular size, water storage conditions and the purity of the dopant has not significantly influenced the morphology or the average size of the particles. The PL and XEOL emission spectra chrome high purity doped alumina revealed a main band near 700 nm, and a dependency on the concentration of chromophore ion, as expected. However, for synthesized samples using recycled chrome ions, neither emission was observed. The physico-chemical and bacteriologic characterization of the recycled water showed that it attends to the standards required from the Brazilian health ministry. Furthermore, during the leaching tests the total chrome concentration was below the equipment detection limits.