Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais
Autor(a) principal: | |
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Data de Publicação: | 2018 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da UFPB |
Texto Completo: | https://repositorio.ufpb.br/jspui/handle/123456789/14841 |
Resumo: | The use of semiconductors as photocatalysts is a promising strategy in the treatment of organic pollutants. In this sense, the photocatalytic performance of lamellar potassium niobates and their protonated forms were tested for the degradation of the model dye Remazol Yelow Gold (RNL). The niobates (KNb3O8 and K4Nb6O17) were prepared by the polymeric precursor (PP) and solid state (SS) methods. The protonated forms HNb3O8.H2O and K4-xHxNb6O17, obtained by the PP method, were prepared via a ion exchange reaction using a HNO3 solution. The materials were characterized by X-ray di?raction (XDR), infrared (IR), Raman, ultraviolet visible (UV-vis), scanning electron microscopy (SEM), surface area (BET) and photoluminescence (PL). Theoretical Computational calculation were performed (DFT) to de?ne the structural and vibrational aspects of niobates in the potassium form. Their structures were characterized at long, medium and short range are in accordance with those in the literature. The theoretical studies of octahedron distortions showed that KNb3O8 has two types of distortion, where as K4Nb6O17 has four types. The octahedron with the largest distortion degree for K4Nb6O17 has a short Nb - O bond (high covalent character) and another much elongated one (with a transient character between the covalent and the ionic). It is observed that niobates in the potassium form have better photocatalytic performances when compared to either their protaned forms or P25. Studies to elucidate the mechanism of discoloration for the potassium niobates used suppressors of •OH, O•- 2 radicals, e- and h+. The results show that the mechanism of photocatalysis is indirect, that is, by the formation of •OH radicals . For KNb3O8 the formation of •OH radicals a high contribution of photogenerated e- in the conduction band is observed, whereas, both e- and h+ are responsible for the formation of these radicals for K4Nb6O17. For the RNL discoloration reaction using KNb3O8 reactional parameters were studied, such as pH, initial concentration of dye (C0), photocatalyst quantity and calcination temperature. Three reuse cycles were analyzed for potassium niobates, which indicated little loss of catalytic activity. |
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Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentaisKNb3O8K4Nb6O17Distorção dos octaedrosFotocatáliseReúsoOctahedron distortionPhotocatalysisReuseCNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICAThe use of semiconductors as photocatalysts is a promising strategy in the treatment of organic pollutants. In this sense, the photocatalytic performance of lamellar potassium niobates and their protonated forms were tested for the degradation of the model dye Remazol Yelow Gold (RNL). The niobates (KNb3O8 and K4Nb6O17) were prepared by the polymeric precursor (PP) and solid state (SS) methods. The protonated forms HNb3O8.H2O and K4-xHxNb6O17, obtained by the PP method, were prepared via a ion exchange reaction using a HNO3 solution. The materials were characterized by X-ray di?raction (XDR), infrared (IR), Raman, ultraviolet visible (UV-vis), scanning electron microscopy (SEM), surface area (BET) and photoluminescence (PL). Theoretical Computational calculation were performed (DFT) to de?ne the structural and vibrational aspects of niobates in the potassium form. Their structures were characterized at long, medium and short range are in accordance with those in the literature. The theoretical studies of octahedron distortions showed that KNb3O8 has two types of distortion, where as K4Nb6O17 has four types. The octahedron with the largest distortion degree for K4Nb6O17 has a short Nb - O bond (high covalent character) and another much elongated one (with a transient character between the covalent and the ionic). It is observed that niobates in the potassium form have better photocatalytic performances when compared to either their protaned forms or P25. Studies to elucidate the mechanism of discoloration for the potassium niobates used suppressors of •OH, O•- 2 radicals, e- and h+. The results show that the mechanism of photocatalysis is indirect, that is, by the formation of •OH radicals . For KNb3O8 the formation of •OH radicals a high contribution of photogenerated e- in the conduction band is observed, whereas, both e- and h+ are responsible for the formation of these radicals for K4Nb6O17. For the RNL discoloration reaction using KNb3O8 reactional parameters were studied, such as pH, initial concentration of dye (C0), photocatalyst quantity and calcination temperature. Three reuse cycles were analyzed for potassium niobates, which indicated little loss of catalytic activity.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPESO uso de semicondutores como fotocatalisadores apresenta-se como estratégia promissora no tratamento de poluentes orgânicos. Nesse sentido, o desempenho fotocatalítico dos Niobatos de Potássio Lamelares e suas formas protonadas foi testado na reação de degradação do corante modelo Remazol Amarelo Ouro (RNL). Os niobatos (KNb3O8 e K4Nb6O17) foram preparados pelo método dos precursores poliméricos (PP) e estado sólido (ES). As formas protonadas, HNb3O8.H2O e K4−xHxNb6O17.nH2O, obtidas pelo método PP, foram preparadas por reação de troca iônica, utilizando uma solução de HNO3. Os niobatos foram caracterizados por difração de raios X (DRX), espectroscopia de absorção na região do infravermelho (IV), do ultravioleta - visível (UV-vis), Raman, fotoluminescência (PL) e microscopia eletrônica de varredura (MEV) em seguida área superficial (BET).Também foram realizados cálculos teóricos a nível DFT para elucidação de aspectos estruturais e vibracionais dos niobatos na forma potássica. Suas estruturas, caracterizadas a longo, médio e curto alcance, estão de acordo com as propostas pela literatura. Estudo teórico das distorções dos octaedros mostrou que o KNb3O8 possui dois tipos de distorções; já o K4Nb6O17 apresenta quatro tipos. O octaedro com maior grau de distorção do K4Nb6O17 possui uma ligação curta Nb-O (maior caráter covalente) e outra bem alongada (com caráter transiente entre o covalente e o iônico). Observa-se que os niobatos na forma potássica possuem os melhores desempenhos fotocatalíticos quando comparados às suas formas protonadas e ao P25. Foram feitos estudos para elucidar o mecanismo de descoloração para os Niobatos de Potássio, utilizando supressores de radicais •OH, O•− 2 e de e− e h+. Os resultados obtidos mostram que o mecanismo de fotocatálise é por via indireta, ou seja, pela formação dos radicais •OH. Para o KNb3O8 a formação dos radicais •OH tem contribuição majoritária dos e− fotogerados na BC; por outro lado, tanto os e− como os h+ são responsáveis pela formação desses radicais para o K4Nb6O17. Para a reação de descoloração utilizando o KNb3O8 parâmetros reacionais foram estudados, como pH, concentração inicial (C0) do corante, quantidade e variação da temperatura de calcinação do foto catalisador. Analisaram três ciclos de reúso para os Niobatos de Potássio, os quais indicam pouca perda de atividade catalítica.Universidade Federal da ParaíbaBrasilQuímicaPrograma de Pós-Graduação em QuímicaUFPBMaia, Ary da Silvahttp://lattes.cnpq.br/0234548596508203Souza, Juliana Kelly Dionízio de2019-06-26T17:57:32Z2019-06-262019-06-26T17:57:32Z2018-08-30info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesishttps://repositorio.ufpb.br/jspui/handle/123456789/14841porAttribution-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nd/3.0/br/info:eu-repo/semantics/openAccessreponame:Biblioteca Digital de Teses e Dissertações da UFPBinstname:Universidade Federal da Paraíba (UFPB)instacron:UFPB2019-06-26T17:57:32Zoai:repositorio.ufpb.br:123456789/14841Biblioteca Digital de Teses e Dissertaçõeshttps://repositorio.ufpb.br/PUBhttp://tede.biblioteca.ufpb.br:8080/oai/requestdiretoria@ufpb.br|| diretoria@ufpb.bropendoar:2019-06-26T17:57:32Biblioteca Digital de Teses e Dissertações da UFPB - Universidade Federal da Paraíba (UFPB)false |
dc.title.none.fl_str_mv |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
title |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
spellingShingle |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais Souza, Juliana Kelly Dionízio de KNb3O8 K4Nb6O17 Distorção dos octaedros Fotocatálise Reúso Octahedron distortion Photocatalysis Reuse CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA |
title_short |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
title_full |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
title_fullStr |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
title_full_unstemmed |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
title_sort |
Avaliação fotocatalítica de niobatos lamelares: influência dos métodos de síntese, aspectos teóricos e experimentais |
author |
Souza, Juliana Kelly Dionízio de |
author_facet |
Souza, Juliana Kelly Dionízio de |
author_role |
author |
dc.contributor.none.fl_str_mv |
Maia, Ary da Silva http://lattes.cnpq.br/0234548596508203 |
dc.contributor.author.fl_str_mv |
Souza, Juliana Kelly Dionízio de |
dc.subject.por.fl_str_mv |
KNb3O8 K4Nb6O17 Distorção dos octaedros Fotocatálise Reúso Octahedron distortion Photocatalysis Reuse CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA |
topic |
KNb3O8 K4Nb6O17 Distorção dos octaedros Fotocatálise Reúso Octahedron distortion Photocatalysis Reuse CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA |
description |
The use of semiconductors as photocatalysts is a promising strategy in the treatment of organic pollutants. In this sense, the photocatalytic performance of lamellar potassium niobates and their protonated forms were tested for the degradation of the model dye Remazol Yelow Gold (RNL). The niobates (KNb3O8 and K4Nb6O17) were prepared by the polymeric precursor (PP) and solid state (SS) methods. The protonated forms HNb3O8.H2O and K4-xHxNb6O17, obtained by the PP method, were prepared via a ion exchange reaction using a HNO3 solution. The materials were characterized by X-ray di?raction (XDR), infrared (IR), Raman, ultraviolet visible (UV-vis), scanning electron microscopy (SEM), surface area (BET) and photoluminescence (PL). Theoretical Computational calculation were performed (DFT) to de?ne the structural and vibrational aspects of niobates in the potassium form. Their structures were characterized at long, medium and short range are in accordance with those in the literature. The theoretical studies of octahedron distortions showed that KNb3O8 has two types of distortion, where as K4Nb6O17 has four types. The octahedron with the largest distortion degree for K4Nb6O17 has a short Nb - O bond (high covalent character) and another much elongated one (with a transient character between the covalent and the ionic). It is observed that niobates in the potassium form have better photocatalytic performances when compared to either their protaned forms or P25. Studies to elucidate the mechanism of discoloration for the potassium niobates used suppressors of •OH, O•- 2 radicals, e- and h+. The results show that the mechanism of photocatalysis is indirect, that is, by the formation of •OH radicals . For KNb3O8 the formation of •OH radicals a high contribution of photogenerated e- in the conduction band is observed, whereas, both e- and h+ are responsible for the formation of these radicals for K4Nb6O17. For the RNL discoloration reaction using KNb3O8 reactional parameters were studied, such as pH, initial concentration of dye (C0), photocatalyst quantity and calcination temperature. Three reuse cycles were analyzed for potassium niobates, which indicated little loss of catalytic activity. |
publishDate |
2018 |
dc.date.none.fl_str_mv |
2018-08-30 2019-06-26T17:57:32Z 2019-06-26 2019-06-26T17:57:32Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
https://repositorio.ufpb.br/jspui/handle/123456789/14841 |
url |
https://repositorio.ufpb.br/jspui/handle/123456789/14841 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.rights.driver.fl_str_mv |
Attribution-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nd/3.0/br/ info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Attribution-NoDerivs 3.0 Brazil http://creativecommons.org/licenses/by-nd/3.0/br/ |
eu_rights_str_mv |
openAccess |
dc.publisher.none.fl_str_mv |
Universidade Federal da Paraíba Brasil Química Programa de Pós-Graduação em Química UFPB |
publisher.none.fl_str_mv |
Universidade Federal da Paraíba Brasil Química Programa de Pós-Graduação em Química UFPB |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da UFPB instname:Universidade Federal da Paraíba (UFPB) instacron:UFPB |
instname_str |
Universidade Federal da Paraíba (UFPB) |
instacron_str |
UFPB |
institution |
UFPB |
reponame_str |
Biblioteca Digital de Teses e Dissertações da UFPB |
collection |
Biblioteca Digital de Teses e Dissertações da UFPB |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da UFPB - Universidade Federal da Paraíba (UFPB) |
repository.mail.fl_str_mv |
diretoria@ufpb.br|| diretoria@ufpb.br |
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1801842949653266432 |