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Previous issue date: 2008-11-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Leather tanneries generate effluents with high content of heavy metals, especially chromium, which is used in the mineral tanning process. Microemulsions have been
studied in the extraction of heavy metals from aqueous solutions. Considering the problems related with the sediment resulting from the tanning process, due to its high content in chromium, in this work this sediment was characterized and microemulsion systems were applied for chromium removal. The extraction process consists in the removal of heavy metal ions present in an aqueous feeding solution (acid digestion solution) by a microemulsion system. First three different solid sludge digestion methods were evaluated, being chosen the method with higher digestion capacity. For this digestion
method, seeking its optimization, was evaluated the influence of granule size, temperature and digestion time. Experimental results showed that the method proposed by USEPA (Method A) was the most efficient one, being obtained 95.77% of sample digestion. Regarding to the evaluated parameters, the best results were achieved at 95?C, 14 Mesh granule size, and 60 minutes digestion time. For chromium removal, three microemulsion
extraction methods were evaluated: Method 1, in a Winsor II region, using as aqueous phase the acid digestion solution; Method 2, in a Winsor IV region, being obtained by the addition of the acid digestion solution to a microemulsion phase, whose aqueous phase is
distilled water, until the formation of Winsor II system; and Method 3, in a Winsor III region, consisting in the formation of a Winsor III region using as aqueous phase the acid digestion solution, diluted in NaOH 0.01N. Seeking to optimize the extraction process only
Method 1 (Systems I, II, and VIII) and Method 2 (System IX) were evaluated, being chosen points inside the interest regions (studied domains) to study the influence of contact time and pH in the extraction percentiles. The studied systems present the following compositions: System I: Surfactant Saponified coconut oil, Cosurfactant 1-Butanol, Oil phase Kerosene, Aqueous phase 2% NaCl solution; System II: Aqueous phase Acid digestion solution with pH adjusted using KOH (pH 3.5); System VIII: Aqueous phase - Acid digestion solution (pH 0.06); and System IX Aqueous phase Distilled water (pH 10.24), the other phases of Systems II, VIII and IX are similar to System I. Method 2 showed to be the more efficient one regarding chromium extraction percentile (up to 96.59% - pH 3.5). Considering that with Method 2 the microemulsion region only appears in the Winsor II region, it was studied Method 3 (System X) for the evaluation and characterization of a triphasic system, seeking to compare with a biphases system. System
X is composed by: Surfactant Saponified coconut oil, Cosurfactant 1-Butanol, Oil phase Kerosene, Aqueous phase Acid digestion solution diluted with water and with its pH adjusted using 0.01N NaOH solution. The biphasic and triphasic microemulsion systems were analyzed regarding its viscosity, extraction efficiency and drop effective diameter. The experimental results showed that for viscosity studies the obtained values were low for all studied systems, the diameter of the drop is smaller in the Winsor II region, with 15.5 nm, reaching 46.0 nm in Winsor III region, being this difference attributed to variations in system compositions and micelle geometry. In chromium extraction, these points showed similar results, being achieved 99.76% for Winsor II system and 99.62% for Winsor III system. Winsor III system showed to be more efficient due to the obtaining of a icroemulsion with smaller volume, with the possibility to recover the oil phase in excess, and the use of a smaller proportion of surfactant and cosurfactant (C/S) / Os curtumes geram efluentes carregados em metais pesados, especialmente o cromo, utilizado no processo de curtimento. Microemuls?es t?m sido estudadas na
remo??o de metais pesados. Considerando o problema encontrado no sedimento gerado no processo de curtimento, pelo elevado teor de cromo, no presente trabalho nos propomos a caracteriz?-lo e aplicar sistemas microemulsionados para remo??o do cromo. O processo
de extra??o consiste em remover o metal de uma alimenta??o aquosa (solu??o ?cida digerida) para uma fase microemuls?o. Iniciou-se a pesquisa avaliando tr?s diferentes m?todos de digest?o de sedimentos, escolhendo-se o m?todo que apresentasse maior
percentual de digest?o, sendo este m?todo otimizado atrav?s de mudan?as no di?metro das part?culas do sedimento, tempo e temperatura de digest?o. Nesse estudo, escolheu-se o m?todo proposto pelo EPA (M?todo A), que se mostrou mais eficiente, obtendo-se um
percentual de 95,77% de digest?o da amostra. Com rela??o aos par?metros avaliados, os melhores resultados foram obtidos com a temperatura a 95?C, granulometria de 14 Mesh e tempo de opera??o de 60 minutos. Para os estudos da extra??o foram utilizados tr?s m?todos: o M?todo 1, que consiste na forma??o de uma regi?o de Winsor II, utilizando a solu??o ?cida digerida como fase aquosa; o M?todo 2, que consiste em utilizar uma microemuls?o cuja fase aquosa ? ?gua destilada e adicionar a solu??o ?cida digerida at? a
obten??o de um sistema de Winsor II; e o M?todo 3, que consiste na forma??o de uma regi?o de Winsor III, utilizando a solu??o ?cida digerida, dilu?da em NaOH 0,01N, como fase aquosa. Para o estudo da otimiza??o da extra??o foram avaliados apenas os M?todos 1
(Sistemas I, II e VIII) e 2 (Sistema IX), escolhendo-se pontos dentro das regi?es de interesse (dom?nio estudado) para estudar a influ?ncia do tempo e do pH no percentual de extra??o. Os sistemas estudados apresentam as seguintes composi??es: Sistema I:
Tensoativo ?leo de coco saponificado, Cotensoativo 1-Butanol, Fase oleosa Querosene, Fase aquosa NaCl 2,0%; Sistema II: Fase aquosa Solu??o ?cida digerida
ajustada c/ KOH (pH 3,5); Sistema VIII: Fase aquosa Solu??o ?cida digerida (pH 0,06) e Sistema IX: Fase aquosa ?gua destilada (pH 10,24), as demais fases dos Sistemas II, VIII e IX s?o semelhantes ao Sistema I. Atrav?s desse estudo, observou-se que o M?todo 2
foi mais eficiente, com percentuais de 96,59% de extra??o, em pH 3,5. Tendo em vista que com a aplica??o do M?todo 2 s? se obt?m os sistemas de Winsor II, estudou-se um sistema capaz de fornecer a regi?o de Winsor III (tr?s fases) para efeito de compara??o da efici?ncia na extra??o do cromo, com um sistema de duas fases (Winsor II) e, assim, constituiu-se o M?todo 3, utilizando o Sistema X. O sistema X apresenta a seguinte
composi??o: Tensoativo ?leo de coco saponificado, Cotensoativo 1-Butanol, Fase oleosa Querosene, Fase aquosa Solu??o ?cida digerida dilu?da em ?gua e ajustado com NaOH 0,01N. As microemuls?es nas regi?es bif?sicas e trif?sicas foram analisadas com rela??o ? viscosidade, extra??o e di?metro efetivo da gota. Os resultados obtidos nas regi?es de W II e WIII foram os seguintes: a viscosidade ? baixa em todos os pontos
estudados e o comportamento dos fluidos ? do tipo Newtoniano; o di?metro da gota ? menor na regi?o de Winsor II, com di?metro de 15,5 nm, atingindo 46 nm em Winsor III, sendo essa varia??o atribu?da ?s composi??es estudadas e ? geometria da micela; os resultados obtidos na extra??o com os dois sistemas foram semelhantes, com 99,76% de extra??o em WII e 99,62 % em WIII. O sistema utilizando WIII mostrou-se mais eficiente na extra??o do cromo devido a obten??o de uma microemuls?o com menor volume, a possibilidade de recuperar o ?leo em excesso e a utiliza??o de uma menor propor??o de cotensoativo e tensoativo (C/T)
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/17692 |
| Date | 10 November 2008 |
| Creators | Melo, Keila Rejane de Oliveira |
| Contributors | CPF:07286937391, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4783139Z0&dataRevisao=null, Moura, Maria Carlenise Paiva de Alencar, CPF:21414130368, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4702157Y9, Barros Neto, Eduardo Lins de, CPF:59545844434, http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4798645D3, Santanna, Vanessa Cristina, CPF:77938780430, http://lattes.cnpq.br/9445575768909084, Peres, Ant?nio Eduardo Clark, CPF:04457641634, http://lattes.cnpq.br/8666548473150908, Dantas, Tereza Neuma de Castro |
| Publisher | Universidade Federal do Rio Grande do Norte, Programa de P?s-Gradua??o em Qu?mica, UFRN, BR, F?sico-Qu?mica; Qu?mica |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | Portuguese |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Format | application/pdf |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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