Adsor??o e dessor??o das esp?cies de ars?nio (III e V) e ?cido monometilars?nico, pela K-jarosita, para proposta de remedia??o ambiental

• Main Author: Hott, Rodrigo de Carvalho
• Other Authors: Rodrigues, Jairo Lisboa
• Language: Portuguese
• Published: UFVJM 2017
• Subjects: K-jarosita; Ars?nio; Adsor??o; Remedia??o ambiental; Arsenic; Adsorption; Environmental remediation
• Online Access: http://acervo.ufvjm.edu.br/jspui/handle/1/1153

Data de aprova??o ausente. === ?rea de concentra??o: Qu?mica Anal?tica. === Submitted by Jos? Henrique Henrique ([e-mail]) on 2016-12-21T17:35:27Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) rodrigo_carvalho_hott.pdf: 1415995 bytes, checksum: f0a923f5addbb9b380763851a41b99e6 (MD5) === Approved for entry into archive by Rodrigo Martins Cruz ([e-mail]) on 2017-01-31T13:51:38Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) rodrigo_carvalho_hott.pdf: 1415995 bytes, checksum: f0a923f5addbb9b380763851a41b99e6 (MD5) === Made available in DSpace on 2017-01-31T13:51:38Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) rodrigo_carvalho_hott.pdf: 1415995 bytes, checksum: f0a923f5addbb9b380763851a41b99e6 (MD5) Previous issue date: 2016 === A elevada toxicidade e potencial de acumula??o de ars?nio em diversos ambientes t?m incentivado pesquisas de novos m?todos de remo??o desse ?on em ?guas contaminadas. Dentre os diversos processos utilizados, a adsor??o contendo ?xidos de ferro tem apresentado bons resultados na remedia??o de ambientes aqu?ticos contaminados por ars?nio. Entretanto, muito do ars?nio liberado no ambiente aqu?tico ? proveniente de efluentes de minera??o, que apresenta meio extremamente ?cido, o que impossibilita a a??o da maioria dos adsorventes utilizados. Neste contexto, a K-jarosita surge como alternativa na remo??o de ars?nio em ambientes contaminados devido sua estabilidade neste ?mbito de baixo pH. Os estudos deste trabalho foram realizados no campus do Mucuri da UFVJM e tiveram como objetivo sintetizar, caracterizar e avaliar atrav?s de ensaios de adsor??o a efetividade de nanopart?culas de k-jarosita na remo??o de ars?nio inorg?nico (III e V) e ars?nio org?nico (?cido monometilars?nico-MMA) em ?gua contaminada, bem como a dessor??o destes elementos promovendo a libera??o dos s?tios de adsor??o dos nanomateriais. A K-jarosita foi caracterizada atrav?s da difratometria de raios-X, com seus pontos de reflex?o estando de acordo com o arquivo padr?o JCPDS 36-427. Seus dados difratom?tricos foram refinados pelo m?todo de Rietveld, caracterizando sua estrutura como rombo?drica de densidade 3,045g cm-3. Apresenta uma ?rea superficial de 9 m2 determinada atrav?s do m?todo BET, sendo uma estrutura mesoporosa, com poros apresentando volume de 0,034 cm3 g-1 e tamanho m?dio de 90?, determinados pelo m?todo BJH. Nos testes de adsor??o, os estudos cin?ticos demonstraram que a K-jarosita apresenta uma r?pida adsor??o, tendo o As(V) sido mais adsorvido que os demais. Com rela??o ao efeito de competi??o de ?nions, foram realizados ensaios com NO3-, PO43- e SO42-, sendo observada pouca interfer?ncia dos ?ons nitrato e fosfato, e um efeito de aumento de adsor??o do ?on sulfato com rela??o ao As (V). No caso do pH, foram avaliadas as faixas de pH do meio ?cido ao meio alcalino, sendo que nestas foi verificada maior estabilidade da K-jarosita em pH pr?ximo de 3, fora do qual ocorre sua desestabiliza??o com forma??o de outros ?xidos de ferro. A dessor??o ocorre em pH acima de 12, sendo o As-i (V) e o As-o MMA os mais facilmente liberados. Foram avaliadas isotermas de Langmuir, Freundlich, Langmuir-Freundlich e Redlich-Peterson, sendo todas adequadas ? adsor??o de ars?nio pela K-jarosita, tendo o modelo de Langmuir-Freundlich apresentado um melhor ajuste. A capacidade m?xima de adsor??o pelas nanopart?culas de K-jarosita foi de 11,12 mg g-1 para As (III), de 18,26 mg g-1 para As (V) e de 13,35 mg g-1 para MMA. Em an?lise de amostras de ?guas superficiais de rios contaminados por ars?nio, provenientes do munic?pio de Paracatu/MG, todas ficaram ap?s a adsor??o por K-jarosita abaixo dos limites estabelecidos pela legisla??o vigente. Foi realizada tamb?m a recupera??o do ars?nio ap?s dessor??o na forma de Ag3AsO4, o qual apresentou grande efici?ncia em ensaios de fotocat?lise, que tamb?m foram realizados. E como forma de funcionalizar o uso das nanopart?culas de K-jarosita, foram desenvolvidos prot?tipos de filtros que apresentaram grande efici?ncia na remo??o do ars?nio em amostras de ?gua. Atrav?s deste estudo, foi poss?vel verificar que a K-jarosita apresenta grande potencial de ser utilizada como forma de remedia??o ambiental em ambientes aquosos contaminados por ars?nio. === Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, [2016]. === The high toxicity and potential of arsenic accumulation in different environments have encouraged works of new ion removal methods in contaminated water. Among the various processes used, the adsorption containing iron oxides has shown good results in the remediation of aquatic environments contaminated by arsenic. However, much of the arsenic is released into the aquatic environment from mining waste, which presents extremely acid medium, which prevents the action of most adsorbents used. In this context, the K-jarosite is an alternative in the removal of arsenic in contaminated environments due to its stability in the context of low pH. Studies of this work were carried out in the Mucuri campus from UFVJM and aimed to synthesize, characterize and evaluate through adsorption tests the effectiveness of K-jarosite nanoparticles in inorganic arsenic removal (III and V) and organic arsenic (monometilars?nic acid -MMA) in contaminated water and desorption of these elements promoting the release of nanomaterials adsorption sites. The K-jarosite was characterized by diffraction of X-rays, with their reflection points are in accordance with the standard file JCPDS 36-427. Its difratom?trics data were refined by the Rietveld method, characterizing its structure and density of rhombohedral 3,045g cm-3. Having a surface area of 9 m2 determined by the BET method, being a mesoporous structure with pores having volume of 0.034 cm3 g-1 and 90 ? average size determined by the BJH method. In adsorption tests, kinetic studies have shown that K-jarosite has a rapid adsorption, and the As (V) was adsorbed more than the others. With respect to anions competition effect, tests were performed with NO3-, PO43- and SO42-, and observed little interference of nitrate and phosphate ions, and sulfate ion adsorption increased effect with respect to As (V). In the case of pH, the pH ranges from acid to alkaline medium were evaluated, and these were verified increased stability of K-jarosite at pH around 3, out of which a destabilization occurs with formation of other iron oxides. The desorption occurs at pH above 12 and the As-i (V) and o-MMA to more easily released. Langmuir isotherms were evaluated, Freundlich, Langmuir-Freundlich and Redlich-Peterson, all being suitable for the adsorption of arsenic by K-jarosite having the model of Langmuir-Freundlich presented a better fit. The maximum adsorption capacity for K-jarosite nanoparticles was 11.12 mg g-1 for As (III) 18.26 mg g-1 to As (V) and 13.35 mg g-1 for MMA . In analysis of surface water samples from contaminated rivers by arsenic, from the Paracatu city / MG, all they were after adsorption by K-jarosite below the limits established by law. It also performed the recovery of arsenic desorbed in the form of Ag3AsO4, which showed great efficiency in photocatalysis tests were also performed. And as a way to functionalize the use of K-jarosite nanoparticles filter prototypes were developed that showed high efficiency in the removal of arsenic in water samples. Through this study, we found that K-jarosite has potential to be used as a form of environmental remediation in aqueous environments contaminated by arsenic.