The Department of Defense (DoD) has numerous sites that contain groundwater contaminated with 2,4,6-trinitrotoluene (TNT). The currently applied technologies for treating TNT contaminated waters are carbon adsorption and chemical oxidation. Carbon adsorption is a non-destructive technology, which could create future liability issues and is inefficient at relatively low TNT concentrations. On the other hand, application of chemical oxidation for the treatment of TNT contaminated water generates trinitrobenzene (TNB), a by-product of the incomplete oxidation of TNT. TNB is regulated as strictly as TNT. Additionally, over 70% of the reactor required treatment time for meeting target levels is due solely for TNB removal. This study evaluated the potential integration of zero-valent metallic species and advanced oxidation for the treatment of waters contaminated with TNT. The idea was to reduce treatment time, and thus, operational costs, when advanced oxidation is used as a stand-alone treatment technology by reducing TNT prior to oxidation. The use of zero-valent metals as the first treatment step transformed TNT into reduced organic compounds which were easily oxidized. The effectiveness of zinc, iron, nickel, copper, and tin as TNT reducing agents was evaluated. Zinc and iron were selected for further study based on their performance degrading TNT. Then, the reduction mechanism (pathway) and associated by-products of TNT reduction using zinc were examined using a zinc specimen manufactured by Sigma Corporation. Three amines were identified during reduction : 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, and 2,4-diamino-toluene. Other intermediates were observed but not identified. Many of these reduction by-products adsorbed strongly onto the metal surface, significantly reducing the rate of TNT degradation during aging experiments. The aging of the metallic species was modeled using a power decay law parameter with the rate expression for TNT degradation. Corrosion promoters such as KCl addition, ozonation, and peroxone were evaluated as alternatives to reactivate zinc and iron to achieve steady TNT degradation. The addition of KCl performed significantly better than ozonation and peroxone. Furthermore, addition of KCl during the reduction step using iron or zinc generated organics that were successfully mineralized by ozonation or peroxone.

Made available in DSpace on 2017-07-10T17:40:49Z (GMT). No. of bitstreams: 1 2014_Tese_Angela_Laufer_Rech.pdf: 2697260 bytes, checksum: a821a9dcb688dc836fc560b40b6280b2 (MD5) Previous issue date: 2014-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The biosorption configures as alternative for the remediation of contaminated waters. Thus, this study aimed to investigate the potential of the use of endocarp of açaí berry (Euterpe oleracea M.) as alternative adsorbent for the removal of Cd2+, Pb2+, Cr3+, Cu2+ and Zn2+ of aqueous contaminated solutions. After the biosorbent characterization by scanning electron microscopy and infrared spectroscopy were performed adsorption tests aiming to determine the ideal conditions of pH, adsorbent mass and contact time for the adsorption process. The kinetics of adsorption was evaluated by the models of pseudo first order, pseudo second order, Elovich and intraparticle diffusion. Also were performed comparative studies with active coal. Besides, were evaluated the desorption capacity of adsorbents and the influence of temperature in the adsorption process. By the obtained results were built adsorption isotherms, which were linearized by mathematical models of Langmuir, Freundlich and Dubinin-Radushkevich. The structural characterization of the biosorbent allowed identifying functional groups such as lignin and celluloses, and the morphological characterization shown a lamelar structure. By the presence of all the above characteristics the biosorbent present favorable conditions for metallic ions adsorption. The studies relating adsorbent mass of endocarp of açaí berry and pH of contaminated solution indicate an ideal pH of 6.0 and 5.0 for Cd2+, Pb2+ and 4.0 for Cr3+, Cu2+ and Zn2+, as well the use of 8, 20 and 12 g L-1 (adsorbent mass by solution volume). The time for dynamic equilibrium for biosorption process was 60 min. The kinetic models suggest for all metallic ions evaluated, the limiting pass for biosorption may be chemisorption. According to adsorption isotherms, the model which represented the best fitting for biosorption of Cd2+, Cr3+, Cu2+ and Zn2+ was Langmuir, indicating a monolayer adsorption. However, for Pb2+ the model with best fitting was Freundlich, which assumes a multilayer adsorption. The values for desorption were low, indicating a strong interaction of the metals with adsorbent surface. The thermodynamic parameters indicate that for Cd2+, Pb2+, Cu2+ and Zn2+ the biosorption process is spontaneous and endothermic. For Cr3+, the process is not spontaneous and from exothermic nature. In general, by the obtained results, it can be concluded that the use of endocarp from açaí berry as biosorbent is an alternative for remediation of contaminated waters, once this material is natural and with low cost and high availability / A biossorção configura como alternativa promissora para a remediação de águas contaminadas. Assim, este trabalho teve como objetivo investigar a potencialidade do uso de caroço de açaí (Euterpe oleracea M.) como adsorvente alternativo na remoção de Cd2+, Pb2+, Cr3+, Cu2+ e Zn2+ de soluções aquosas monoelementares fortificadas. Após a caracterização do biossorvente por meio de microscopia eletrônica de varredura e espectroscopia na região do infravermelho, foram realizados testes de adsorção objetivando determinar as condições ideais de pH, massa de adsorvente e tempo de contato para o processo de adsorção. A cinética de adsorção foi avaliada pelos modelos de pseudoprimeira ordem, pseudossegunda ordem, Elovich e difusão intrapartícula. Ainda, foram realizados estudos comparativos com o carvão ativado. Além disso, foram avaliados a capacidade de eluição dos adsorventes e a influência da temperatura no processo de adsorção. A partir dos resultados obtidos, foram construídas as isotermas de adsorção, as quais foram linearizadas conforme os modelos matemáticos de Langmuir, Freundlich e Dubinin-Radusckevich. A caracterização estrutural do biossorvente permitiu identificar grupos funcionais que indicam a presença de lignina e celulose, e a caracterização morfológica indicou uma estrutura lamelar, assim, por apresentar tais características, o biossorvente apresenta condições favoráveis para a adsorção dos íons metálicos estudados. Os estudos em função da massa do biossorvente caroço de açaí e do pH das soluções aquosas indicaram, o pH ideal de 6,0 e 5,0 para Cd2+, Pb2+ e de 4,0 para Cr3+, Cu2+ e Zn2+, bem como, a utilização de 8, 20 e 12 g L-1 (massa do biossorvente por volume de solução) para Cd2+, Pb2+ e Cr3, respectivamente, e a utilização de 8 g L-1 para Cu2+ e Zn2+. O tempo de equilíbrio dinâmico ideal para o processo de biossorção foi de 60 min. Com a aplicação dos modelos cinéticos sugere-se que para todos os íons metálicos estudados, o principal passo limitante para a biossorção pode ser a quimiossorção. Quanto às isotermas de adsorção, o modelo que representou o melhor ajuste para a biossorção de Cd2+, Cr3+, Cu2+ e Zn2+ foi o de Langmuir, indicando uma adsorção em monocamadas. Já, em termos do íon Pb2+, o modelo que melhor se ajustou foi o de Freundlich, o qual assume que a adsorção ocorre em sistema de multicamadas. Os valores de eluição foram baixos, indicando uma forte interação dos metais com a superfície do adsorvente. Os parâmetros termodinâmicos indicaram que, para os íons Cd2+, Pb2+, Cu2+ e Zn2+ o processo de biossorção é espontâneo e endotérmico. Para o íon Cr3+, o processo não é espontâneo e apresenta natureza exotérmica. De maneira geral, pelos resultados obtidos, pode-se concluir que a utilização de caroço de açaí como biossorvente é uma alternativa para remediação de águas contaminadas, uma vez que este material é natural, de baixo custo e de alta disponibilidade