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No. of bitstreams: 2 license_rdf: 22974 bytes, checksum: 99c771d9f0b9c46790009b9874d49253 (MD5) Disserta??o Completa Times New Roman - Com Assinatura da Ban.pdf: 4476480 bytes, checksum: 309e034f51cd7605224651743ecee1cd (MD5) Previous issue date: 2012 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) / Filmes finos de di?xido de estanho dopados com antim?nio foram confeccionados pelo m?todo de deposi??o t?rmica sobre micro tela de a?o ASTM 316 objetivando a confec??o de anodos perme?veis a fluido para uso em reatores filtro-prensa. Os ?xidos nas formas de filmes suportados e de p? foram investigados pelas t?cnicas de energia dispersiva de raios-X (EDX), difratometria de raios-X (DRX) e microscopia eletr?nica de varredura (MEV). O estudo de EDX revelou que a raz?o efetiva Sb/Sn nos filmes ? maior que a nominal, enquanto que o DRX revelou que o SnO2 est? presente na forma da estrutura da cassiterita, que n?o h? presen?a de picos relacionados a ?xidos de antim?nio e que o aumento da concentra??o de Sb leva a uma diminui??o da cristalinidade dos filmes. O estudo de MEV revelou que os filmes apresentam estrutura compacta e n?o-porosa. A caracteriza??o eletroqu?mica dos anodos 316/Sb-SnO2 conduzida numa c?lula do tipo eletr?lito polim?rico s?lido (EPS) empregando-se a membrana Nafion? 117 da Dupont revelou a partir da voltametria c?clica e das curvas de polariza??o que o sobrepotencial para a rea??o de desprendimento de oxig?nio (RDO) aumenta com a concentra??o de antim?nio. O estudo envolvendo a an?lise da durabilidade dos anodos conduzido em condi??es galvanost?ticas (20 mA cm-2) revelou que a vida ?til do anodo aumenta com a concentra??o de Sb passando por um ponto de m?ximo. O anodo 316/Sb-SnO2 alojado em c?lula do tipo EPS na condi??o de ?zero-gap? e na aus?ncia de eletr?litos l?quidos foi aplicado na degrada??o eletroqu?mica do corante t?xtil Cibacron? Marinho F-4G considerado como poluente modelo. A cin?tica de descolora??o seguiu o modelo de pseudo-primeira ordem representativo do controle difusional atrav?s da microestrutura do ?nodo sob influ?ncia da turbul?ncia causada pelo desprendimento de oxig?nio. Foi verificada uma descolora??o superior a 90% e uma degrada??o do composto parental maior que 50% ap?s 3,5 h de eletr?lise. A an?lise das curvas cronopotenciom?tricas indicou que a desativa??o dos anodos ? fortemente influenciada pela disponibilidade dos radicais hidroxilas adsorvidos na superf?cie do eletrodo. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2012. / ABSTRACT Thin films of tin dioxide doped with antimony were prepared by the thermal decomposition method onto a stainless steel fine mesh (ASTM 316) in order to obtain a fluid permeable anode for application in filter-press reactors. Films and powders of Sb-SnO2 were investigated using the energy dispersive X-ray (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The EDX revealed that the effective Sb/Sn molar ratio in films is greater than the nominal composition, while the XRD has revealed that SnO2 is present in the crystalline form of the cassiterite structure. In addition, it was verified the absence of peaks accounted for the antimony oxides even for higher amounts of Sb, while the addition of Sb lead to a decrease in the film crystallinity. SEM images showed that the thin films are rather compact. The electrochemical characterization of the fluid permeable anode composed of 316/Sb-SnO2 was carried out in an SPE cell using the Nafion? 117 membrane as the electrolyte. Cyclic voltammograms and polarization curves showed the overpotential for the oxygen evolution reaction (OER) increases upon increasing the antimony concentration. The endurance test carried out under galvanostatic conditions (20 mA cm-2) has revealed that the anode service life increases upon increasing the Sb concentration passing through a maximum. The 316/Sb-SnO2 anode housed in an SPE cell in the zero-gap condition and in the absence of liquid electrolytes was applied on degradation of the Cibacron? Marinho F-4G dye, considered as the pollutant model. Discoloration kinetics was described by the pseudo-first order model describing the diffusion control across the anode microstructure under the influence of the turbulence caused by the OER. A discoloration percentage higher than 90% and a degradation percentage of the parental compound greater than 50% were both achieved after 3.5 h of electrolysis. Analysis of the chronopotentiometric curves indicated the anode deactivation is considerable effected by the availability of the hydroxyl radicals adsorbed on the anode surface.