Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-06T17:51:26Z 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) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2016-01-07T12:06:06Z (GMT) 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) / Made available in DSpace on 2016-01-07T12:06:06Z (GMT). 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.

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-19T13:03:29Z No. of bitstreams: 5 lindomar.pdf: 4197857 bytes, checksum: 529e21e13238b7b71e5ddffb7f4e7b91 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2111 bytes, checksum: f5c843397da71f5d32b775fd8c4cbf56 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-20T09:29:04Z (GMT) No. of bitstreams: 5 lindomar.pdf: 4197857 bytes, checksum: 529e21e13238b7b71e5ddffb7f4e7b91 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2111 bytes, checksum: f5c843397da71f5d32b775fd8c4cbf56 (MD5) / Made available in DSpace on 2015-02-20T09:29:04Z (GMT). No. of bitstreams: 5 lindomar.pdf: 4197857 bytes, checksum: 529e21e13238b7b71e5ddffb7f4e7b91 (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2111 bytes, checksum: f5c843397da71f5d32b775fd8c4cbf56 (MD5) Previous issue date: 2013-12-17 / Eletrodos constitu?dos de ?-PbO2 foram preparados via eletrodeposi??o, mediante inclus?o dos ?ons Fe3+ e F- na mistura precursora, usando como substratos tela de a?o (ASTM 316) e tecido de carbono, visando a produ??o eletroqu?mica de oz?nio (PEO) em um reator filtro-prensa conduzida na aus?ncia de eletr?lito l?quido. A an?lise das micrografias de MEV para ambos substratos revelaram que em baixas concentra??es dos dopantes houve a forma??o de gr?os bem definidos com uma ?rea superficial uniforme. A an?lise de Raios-X para ambos substratos revelou o desfavorecimento da forma??o da fase ?-PbO2 para a maioria da concentra??o dos dopantes. Estudos cronopotenciom?tricos evidenciaram a estabilidade dos anodos quando sujeitados a intensa evolu??o de gases. Para o eletrodo dopado com 1 mM do ?on Fe3+, a efici?ncia de corrente da PEO foram de 10% e 9,5% com uma velocidade de gera??o de oz?nio de 1,35 g h-1 e 1,40 g h-1 para os substratos de tela de a?o e de tecido de carbono, respectivamente. Os resultados encontrados s?o promissores indicando uma viabilidade do uso desses eletrodos para aplica??o no tratamento de ?gua, por isso, empregou-se o oz?nio produzido eletroquimicamente para tratar ?gua residu?ria proveniente da produ??o de biodiesel na planta piloto da UFVJM. O tratamento oxidativo da ?gua residu?ria foi conduzido num reator em coluna de bolhas via rea??o direta (oz?nio molecular), indireta (radical hidroxila) e mista (O3/HO?) manipulando-se o pH do meio reacional.A caracteriza??o do efluente ozonizado foi efetuada monitorando-se o processo de degrada??o da mat?ria org?nica dissolvida via espectrofotometria. A cin?tica do processo de degrada??o seguiu o modelo de pseudo-primeira ordem. Foi verificado que a constante cin?tica sofre varia??o com o tempo de ozoniza??o revelando, portanto, uma varia??o da recalcitr?ncia com o tempo de rea??o. A demanda de energia requerida no processo de ozoniza??o foi caracterizada por uma energia el?trica por ordem (EEO) de 139 kW h m-3 ordem-1. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2013. / ABSTRACT Electrodes comprised of ?-PbO2 were prepared by electrodeposition, by moans of the inclusion of Fe3+ and F- ions in the precursor mixture, using as substrates steel screen (ASTM 316) and carbon cloth in order to produce ozone in an filter-press electrochemical reactor conducted in the absence of liquid electrolyte. The analysis of SEM micrographs revealed that for both substrates at low dopants concentrations resulted in the formation of well-defined grains with a uniform surface area. X-rays analysis for both substrates showed the inhibition of formation of the ?-PbO2 phase for most of the dopant concentration. Cronopotenciometric studies revealed a good stability of the anodes when they were subjected to the intense gas evolution. For the electrode doped with 1 mM Fe3+, the current efficiency of EOP were 10% and 9.5% for an ozone generation rate of 1.35 g h-1 and 1.40 g h -1 using the steel screen and carbon cloth substrates, respectively. These results are promising, indicating a feasibility of using these electrodes for application in water purification, so the electrochemical ozone produced was applied to treat residuary water obtained from the biodiesel produced in the pilot plant of UFVJM. The oxidative chemical treatment of wastewater was conducted in a bubble column reactor via direct (molecular ozone), indirect (hydroxyl radical) and mixed (O3/HO?) oxidation reaction thrush manipulating the pH of the reaction medium. The characterization of ozonated effluent was assessed by means of monitoring the degradation of the dissolved organic matter using spectrophotometry. The kinetics of the degradation process followed a pseudo-first order model. It was found that the rate constant changes on the ozonation time thus indicating a recalcitrance variation with the reaction time. The energy demand required in the ozonation process was described by an electric energy per order (EEO) of 139 kW h m-3 order-1.