Com o grande uso de agrotóxicos, aumentaram também os problemas relacionados à contaminação. Tentando remediar esses problemas, estudos baseados em processos oxidativos avançados, como a reação de Fenton, tem conseguido notoriedade, pois o radical hidroxila (•OH) ataca os poluentes orgânicos de maneira não seletiva. Porém, tal reação em meio homogêneo não é tão atrativa, pois requer grandes quantidades de íons de ferro em solução em meio ácido. Entretanto, pesquisas demostram que é possível desenvolve-la em meio heterogêneo com uma variedade de catalisadores em condições mais brandas e, ainda sim, gerar radicais livres e promover a oxidação de contaminantes orgânicos em várias faixas de pH. Nesse sentido, o presente trabalho teve como objetivos o enriquecimento do rejeito magnético, subproduto da extração de fosfato, em magnetita e a avaliação da viabilidade do mesmo nas reações do tipo Fenton heterogênea, tendo como modelo o herbicida hexazinona. Primeiramente o material passou por separação granulométrica, onde foram geradas 7 amostras, de acordo com a abertura de cada peneira. Em seguida elas foram submetidas a redução do tamanho de suas partículas em moinhos de bolas e passaram por uma pré-caracterização por espectroscopia de florescência de raio-x, difração de raio-x, termogavimetria, calorimetria diferencial exploratório e análise do tamanho de suas partículas. De posse desses dados, todas as amostras foram submetidas ao ensaio de lixiviação ácida, para o enriquecimento do material em magnetita. Após esta etapa, uma amostra foi escolhida (MESH 28) e submetida novamente a lixiviação ácida e às etapas de caracterização anterior e também, a análise do tamanho de sua área superficial, microscopia eletrônica de varredura, e comportamento magnético qualitativo. Assim, a amostra escolhida foi empregada para catálise heterogênea, de acordo com um planejamento estatístico do tipo composto central, levando em consideração a concentração de H2O2 e a variabilidade do pH da solução. Os resultados obtidos mostram que nas condições testadas, a que se apresenta com maior potencial para aplicações reais é a que se utiliza de concentração de peróxido igual a 0,0625 mol/L e pH 7,5, podendo ser ainda \"otimizada\" através de estudos em condições próximas a esta. Portanto, o resíduo magnético enriquecido em magnetita tem potencialidade para ser utilizado como catalisador em reações do tipo Fenton para degradação de herbicidas em água. / With the heavy use of pesticides, also increased the contamination-related problems. Trying to reduce these problems, studies based on advanced oxidation processes, such as the Fenton reaction, has achieved notoriety because the hydroxyl radical (•OH) attacks organic pollutants in a non-selective manner. However, such reaction in homogeneous medium is not so attractive because it requires large amounts of iron ions in solution in acidic medium. However, studies demonstrate that it is possible to develop it in a heterogeneous medium with a variety of catalysts in milder conditions and, yet, generate free radicals and promoting the oxidation of organic contaminants in various pH ranges. In this sense, the present study aimed to enrich the magnetic waste, by-product of phosphate extraction in magnetite and evaluate it viability of the reactions of the heterogeneous Fenton type, with reference to the hexazinone herbicide. Firstly, the material passed to granulometric separation, where were generated seven samples according to the opening of each sieve. Then they were subjected to size reduction of their particles in ball mills and passed through a pre-characterization by X-ray fluorescence, X-ray diffraction, thermogravimetry, calorimetry exploratory differential and analysis of its particle size. With this data, all samples were subjected to acid leaching test, to enrich the material with magnetite. After this step, a sample was selected (MESH 28) and resubmitted to acid leaching and to the previous steps of characterization of steps and also the analysis of the size of its surface area, electronic scanning microscopy and magnetic behavior qualitative. Thus, the chosen sample was used for heterogeneous catalysis, in accordance with the central composite statistic planning type, taking into consideration the concentration of H2O2 and the pH variability of the solution. The results show that under the conditions tested, that presents the greatest potential for real world applications is that utilizes peroxide concentration equal to 0.0625 mol/L and pH 7,5, can yet be \"optimized\" via studies in conditions close to this. Therefore, the magnetic residue enriched in magnetite has the potential to be used as a catalyst type in Fenton reactions for the degradation of herbicides in water.

A magnetita, também chamada de ferrita de ferro, é um minério conhecido como imã natural e encontrada em depósitos de ferro. Além desse comportamento intrínseco, a magnetita possui a capacidade de remover os íons metálicos do meio aquoso por fenômenos de adsorção. O seu caráter fortemente magnético a distingue de outros tipos de adsorventes, visto que, é facilmente removida da solução por separação magnética. Neste trabalho estudou-se a adsorção de urânio(VI), na forma de íons UO22+, de solução nítrica pela magnetita sintética. Esta foi preparada por precipitação simultânea adicionando-se uma solução de NaOH à solução contendo os íons Fe2+ e Fe3+. A magnetita sintética, na forma de um pó preto, exibiu uma resposta magnética de atração intensa na presença de um campo magnético, sem contudo tornar-se magnética, um comportamento típico de material superparamagnético constatado por medidas de magnetização. Estudou-se a influência dos parâmetros de adsorção de íons UO22+ tais como o pH, a dose do adsorvente, tempo de contato e a isoterma de equilíbrio. A máxima adsorção de urânio foi encontrada no intervalo de pH entre 4 e 5. Verificou-se que quanto maior a dose de magnetita menor a capacidade de adsorção e maior a remoção de U. Da relação entre adsorção e tempo de contato verificou-se que a remoção aumentou rapidamente com o tempo e atingiu-se a condição de equilíbrio em 30 min. Os resultados da isoterma de equilíbrio apresentaram maior concordância com o modelo de Langmuir, o qual permitiu a determinação da capacidade teórica de saturação da magnetita para o urânio. A interação entre os íons UO22+ e a magnetita foi caracterizada como uma adsorção química e espontânea. / Magnetite, also known as iron ferrite, is a mineral iron and a natural magnet found in iron deposits. In addition to its magnetic intrinsic behavior, the magnetite has the capacity to remove the metallic ions from aqueous medium by adsorption phenomena. The strong magnetic character of magnetite distinguishes it from other adsorbent types, which it allows to be readily removed from solution by magnetic separation. In this work, uranium (VI) adsorption, as UO22+ ions, from nitric solution by synthetic magnetite was investigated. It was prepared by simultaneous precipitation process, adding a NaOH solution into a solution containing Fe2+ and Fe3+ ions. The synthetic magnetite, a black powder, has exhibited a strong magnetic response in presence of a magnetic field, without nevertheless becomes magnetic. This typical superparamagnetic behavior was confirmed by magnetization measurements. Adsorption parameters of UO22+ ions such as pH. the adsorbent dose, contact time and equilibrium isotherm were evaluated. Maximum uranium adsorption was observed in the pH 4.0-5.0 range. It was noticed that increase in magnetite dose increased the percent removal of uranium, but decreased the adsorption capacity of the magnetite. It was observed from the relation between adsorption and contact time that the removal has increased very fast with time, and achieved the equilibrium within 30 minutes. The results of equilibrium isotherm agreed well with the Langmuir model, and so the theorical saturation capacity of the magnetite was determined for uranyl ions. The interaction between UO22+ ions and the magnetite was defined as a spontaneous chemical adsorption.

The climatic history of the planet Earth is characterized by long- and short-term climatic variations. Oxygen isotopic data clearly shows how during the Cenozoic (from 65 Ma to the present) our planet shifted over time, from greenhouse to icehouse climate states up to the present. Along this progressive cooling, the record is dotted by rapid warming and cooling transient events, from which the causes are not yet fully understood. One problem with paleoceanographic reconstructions is that the older the event, the harder it is to find a sedimentary record in which the paleoclimatic proxies are preserved enough to be used with confidence. This work has the goal of illustrating the possibility to develop a new paleoenvironmental indicator based on the magnetic properties of magnetite crystals synthetized by magnetotactic bacteria. The sensibility of such crystals to small changes in dissolved oxygen content in the pore water and water column is well known, and can be exploited to reconstruct such changes from the sedimentary record. Qualitative information regarding this topic are defined in scientific literature, but, so far, no quantitative study has been performed. This is the first attempt to quantify the preservation of biogenic magnetite as a function of oxygenation state of waters, and is based on recent sediment extracted from cores collected in the coastal region of Rio de Janeiro (Saco do Mamanguá, Paraty). From these, where it was possible to obtain magnetic data relative to magnetite crystals together as well with as direct measurements of pore water chemistry. The results of this first attempt were used to analyze climatic and oceanographic conditions in two other sites, representative of key past environmental events during the Paleocene. The first case study was performed in a newly descripted sedimentary outcrop in central Turkey, of middle Eocene age, representative of a period of rapid warming (Middle Eocene Climatic Optimum, MECO). The second case study was done using material from a marine sediment core collected in the Ross Sea (Antarctica) that covers from the late Eocene to the Middle Miocene, a period that saw the onset of the modern, permanent ice sheet cover in the Antarctic continent. / A historia climática da Terra é caracterizada por variações climáticas de curto e longo prazo, com variações de condições, as vezes extremas. Dados de isótopos de oxigênio mostram claramente que durante o Cenozoico (desde 65 Ma até o presente) o nosso planeta passou de uma fase quente caracterizada por marcado efeito estufa (durante o Paleoceno) para um período progressivamente mais frio em direção ao presente. Ambos esses estados são caracterizados pela alternância de eventos transientes quentes e frios de relativa curta duração, sendo que destes a maioria ainda não é plenamente compreendida. Um dos principais problemas das reconstruções paleoceangráficas é que quanto mais antigo o evento mais difícil encontrar sequências sedimentares cujo registro de proxies paleoambientais seja preservado e confiável. Este trabalho visa explicitar a possibilidade de desenvolver um novo indicador paleoambiental, baseado em propriedades magnéticas de cristais de magnetita biosintetizados por bactérias magnetotáticas. Tais cristais biogênicos são notavelmente sensíveis a pequenas variações de oxigênio dissolvido na coluna de água e na agua intersticial entre os poros dos sedimentos marinhos, e essa sensibilidade pode ser explorada para reconstruir variações climáticas no registro sedimentar do passado. Informações qualitativas estão disponíveis na literatura cientifica mas, até agora, não existem estudos que quantifiquem essa relação. Esta primeira tentativa de quantificar a preservação de magnetita biogênica em função do estado de oxigenação de águas se baseia em testemunhos coletados na costa do estado do Rio de Janeiro (Saco do Mamanguá, Paraty), onde foi possível coletar dados magnéticos relativos aos cristais de magnetita biogênica concomitantemente a medidas diretas de química da água intersticial. Os resultados desse primeiro estudo foram aplicados para reconstruções de variações climáticas e oceanográficas em duas seções que registram importantes mudanças climáticas durante o Paleogeno. No primeiro caso, um afloramento localizado na Turquia central de idade Eocenica e representativo de um período de rápido aquecimento (Ótimo Climático do Eoceno Médio, Middle Eocene climatic Optimum, MECO). No segundo caso, um testemunho coletado no Mar de Ross (Antártica) que abrange o período entre o Eoceno superior e o Mioceno médio, durante o qual houve a formação da primeira cobertura de gelo permanente no continente antártico.

Considerando o grande interesse na produção de materiais provenientes de fontes renováveis, biocompatíveis e que combinem as propriedades de dois ou mais componentes em um único material, buscou-se contribuir para com estudos sobre a incorporação de nanopartículas (NPs) de magnetita (Fe3O4) em filmes preparados a partir de polpa celulósica de sisal e de acetatos obtidos usando esta polpa. Pretendeu-se obter filmes compósitos com boas propriedades magnéticas e com propriedades mecânicas similares ou melhores que aquelas dos filmes puros. Optou-se por polpa celulósica de sisal pelo fato de a planta ser largamente produzida no país, além de ter rápido crescimento e fibras com alto teor de celulose. A magnetita foi escolhida devido a sua baixa toxicidade quando comparada as NPs metálicas e pelo seu potencial de aplicação em diversas áreas, incluindo a médica. A magnetita foi obtida por decomposição térmica (método do poliol) e caracterizada via microscopia eletrônica de transmissão (MET), difração de raios X (DRX) e por magnetometria via SQUID (superconducting quantum interference device). Os resultados indicaram que as NPs preparadas corresponderam a um sistema de partículas esféricas e monodispersas, com diâmetro médio de 5,1 ± 0,5 nm e comportamento superparamagnético a temperatura ambiente. Os filmes foram preparados a partir da dissolução da polpa celulósica (2 g) em dimetilacetamida/cloreto de lítio (DMAc/LiCl), a 160 °C, com ou sem NPs (0,5; 1,4 e 3,0 g L-1) e caracterizados quanto a microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva de raios X (EDX), DRX, propriedades de tração e magnetometria de amostra vibrante (VSM, Vibrating Sample Magnetometry). Resultados de absorção atômica (Li) e análise elementar (N) mostraram que LiCl e DMAc foram praticamente eliminados dos filmes. O aumento da concentração das NPs de magnetita nos filmes compósitos tornou-os menos rígidos, com maior resistência à tração e maior alongamento quando comparado ao filme de celulose. A magnetização de saturação dos filmes compósitos (23; 31; 37 emu g-1) se correlacionou positivamente com o aumento da concentração de NPs. A ausência de histerese e coercividade indicaram que a temperatura ambiente os filmes compósitos são superparamagnéticos. Posteriormente, a celulose foi acetilada em DMAc/LiCl, a 110 °C por 4 h, e acetatos com diferentes graus de substituição (GS) foram obtidos.Filmes compósitos a partir destes acetatos foram obtidos em DMAc/LiCl (condições similares aquelas dos filmes de celulose), na ausência e na presença de NPs (3,0 g L-1). A caracterização destes filmes foi feita por DRX, MEV, EDX, TG e DSC, ensaio de tração e VSM. As imagens MEV mostraram que os filmes de acetatos com diferentes GS apresentaram morfologias distintas e que a introdução das NPs nas matrizes dos diferentes acetatos não teve efeito sobre a morfologia dos filmes. Filmes a partir de acetatos de GS maior ou igual a 2,0 apresentaram microesferas em sua superfície. Filmes de acetatos mais substituídos foram menos resistentes à tração que os filmes de acetatos mais substituídos e a inserção de NPs nessas matrizes levou a filmes menos rígidos. No geral, filmes compósitos apresentaram menores índices de cristalinidades e decomposição térmica com início a temperaturas inferiores (entre 220 e 270 °C) em relação ao respectivo filme de acetato (controle, entre 280-300 °C), mas sem comprometer as possibilidades de aplicação. Os filmes compósitos baseados nos acetatos de celulose apresentaram comportamento superparamagnético a temperatura ambiente, com temperatura de bloqueio de 14 K e boa magnetização de saturação (27-46 emu.g-1). Não foi observado correlação entre GS e propriedades magnéticas dos filmes, as quais mostraram certa dependência da presença ou não de microesferas. A associação das NPs de magnetita nas matrizes poliméricas, tanto de celulose como de acetato de celulose, levou a filmes poliméricos com boas propriedades magnéticas e mecânicas. / Considering the great interest in the production of materials from renewable sources and biocompatible ,and that combining the properties of two or more components in a single material, the aim was to contribute to studies on the incorporation of magnetite nanoparticles (NPs) (Fe3O4) in films produced from sisal pulp or acetates from this pulp. To obtain composite films with good magnetic properties, as well as mechanical properties similar or better than those of the pure films was also intended. The sisal pulp was chosen due to the fact that the plant is widely produced, not to mention its rapid growth and fibers with a high cellulose concentration. Magnetite was chosen due to its low toxicity when compared with metallic NPs and its potential application in several areas, including the medical area. The magnetite was obtained by thermal decomposition (polyol method) and characterized by transmission and scanning electron microscopy (TEM), X-ray diffraction (XRD) and by SQUID magnetometry (superconducting quantum interference device).The results showed that the prepared NPs correspond to a system of spherical and monodisperse particles with a mean diameter of 5.1 ± 0.5nm and superparamagnetic behavior at room temperature. The films were prepared by dissolving cellulosic pulp (2 g) in dimethylacetamide/lithiumchloride (DMAc/LiCl) to 160°C, with or without NPs (0.5, 1.4 and 3.0 g g L-1) and characterized by electron microscopy (SEM), energy dispersive X-ray spectrum (EDX), XRD, tensile properties and vibrating sample magnetometry (VSM). Results of atomic absorption (Li) and elemental analysis (N) showed that LiCl and DMAc were practically eliminated from the films. Increasing the concentration of magnetite NPs in the composite films made them less rigid, with higher tensile strength and elongation when compared to the cellulose film. The saturation magnetization of the composite films (23, 31, and 37 emu g-1) was positively correlated with the concentration of NPs. The lack of hysteresis and coercivity indicated that the composite films are superparamagnetic at room temperature. Subsequently, cellulose was acetylated in DMAc/LiCl, at 110°C for 4h, and acetates with different degrees of substitution (DS) were obtained. Composite films from these acetates were obtained in DMAc/LiCl (conditions similar to those of the cellulose films) in the absence and presence of NPs (3.0 g L-1).The characterization of these films was performed by XRD, SEM, EDX, TG and DSC, tensile testing and VSM. SEM images showed that acetate films with different DS exhibited different morphologies and that the introduction of NPs in the matrices of different acetates had no effect on the morphology of the films. Films from acetates of DS greater than or equal to 2.0 showed microspheres on its surface. Acetate films more substituted were less resistant to traction than acetate films less substituted and the inclusion of NPs in these matrices led to less rigid films. Overall, composite films exhibited lower levels of crystallinity and thermal decomposition starting at lower temperatures (between 220-270°C) compared to the corresponding acetate film (control) (between 280-300°C), but without compromising the ability of application. The composite films based on cellulose acetate showed superparamagnetic behavior at room temperature with blocking temperature of 14 K and good saturation magnetization (27-46 emu.g-1). No correlation between DS and the magnetic properties of the films was observed, which showed some dependence on the presence or absence of microspheres. The association of the NPs in the polymeric matrices of both cellulose and cellulose acetate led to polymeric films with good magnetic and mechanical properties.

Considerando o grande interesse na produção de materiais provenientes de fontes renováveis, biocompatíveis e que combinem as propriedades de dois ou mais componentes em um único material, buscou-se contribuir para com estudos sobre a incorporação de nanopartículas (NPs) de magnetita (Fe3O4) em filmes preparados a partir de polpa celulósica de sisal e de acetatos obtidos usando esta polpa. Pretendeu-se obter filmes compósitos com boas propriedades magnéticas e com propriedades mecânicas similares ou melhores que aquelas dos filmes puros. Optou-se por polpa celulósica de sisal pelo fato de a planta ser largamente produzida no país, além de ter rápido crescimento e fibras com alto teor de celulose. A magnetita foi escolhida devido a sua baixa toxicidade quando comparada as NPs metálicas e pelo seu potencial de aplicação em diversas áreas, incluindo a médica. A magnetita foi obtida por decomposição térmica (método do poliol) e caracterizada via microscopia eletrônica de transmissão (MET), difração de raios X (DRX) e por magnetometria via SQUID (superconducting quantum interference device). Os resultados indicaram que as NPs preparadas corresponderam a um sistema de partículas esféricas e monodispersas, com diâmetro médio de 5,1 ± 0,5 nm e comportamento superparamagnético a temperatura ambiente. Os filmes foram preparados a partir da dissolução da polpa celulósica (2 g) em dimetilacetamida/cloreto de lítio (DMAc/LiCl), a 160 °C, com ou sem NPs (0,5; 1,4 e 3,0 g L-1) e caracterizados quanto a microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva de raios X (EDX), DRX, propriedades de tração e magnetometria de amostra vibrante (VSM, Vibrating Sample Magnetometry). Resultados de absorção atômica (Li) e análise elementar (N) mostraram que LiCl e DMAc foram praticamente eliminados dos filmes. O aumento da concentração das NPs de magnetita nos filmes compósitos tornou-os menos rígidos, com maior resistência à tração e maior alongamento quando comparado ao filme de celulose. A magnetização de saturação dos filmes compósitos (23; 31; 37 emu g-1) se correlacionou positivamente com o aumento da concentração de NPs. A ausência de histerese e coercividade indicaram que a temperatura ambiente os filmes compósitos são superparamagnéticos. Posteriormente, a celulose foi acetilada em DMAc/LiCl, a 110 °C por 4 h, e acetatos com diferentes graus de substituição (GS) foram obtidos.Filmes compósitos a partir destes acetatos foram obtidos em DMAc/LiCl (condições similares aquelas dos filmes de celulose), na ausência e na presença de NPs (3,0 g L-1). A caracterização destes filmes foi feita por DRX, MEV, EDX, TG e DSC, ensaio de tração e VSM. As imagens MEV mostraram que os filmes de acetatos com diferentes GS apresentaram morfologias distintas e que a introdução das NPs nas matrizes dos diferentes acetatos não teve efeito sobre a morfologia dos filmes. Filmes a partir de acetatos de GS maior ou igual a 2,0 apresentaram microesferas em sua superfície. Filmes de acetatos mais substituídos foram menos resistentes à tração que os filmes de acetatos mais substituídos e a inserção de NPs nessas matrizes levou a filmes menos rígidos. No geral, filmes compósitos apresentaram menores índices de cristalinidades e decomposição térmica com início a temperaturas inferiores (entre 220 e 270 °C) em relação ao respectivo filme de acetato (controle, entre 280-300 °C), mas sem comprometer as possibilidades de aplicação. Os filmes compósitos baseados nos acetatos de celulose apresentaram comportamento superparamagnético a temperatura ambiente, com temperatura de bloqueio de 14 K e boa magnetização de saturação (27-46 emu.g-1). Não foi observado correlação entre GS e propriedades magnéticas dos filmes, as quais mostraram certa dependência da presença ou não de microesferas. A associação das NPs de magnetita nas matrizes poliméricas, tanto de celulose como de acetato de celulose, levou a filmes poliméricos com boas propriedades magnéticas e mecânicas. / Considering the great interest in the production of materials from renewable sources and biocompatible ,and that combining the properties of two or more components in a single material, the aim was to contribute to studies on the incorporation of magnetite nanoparticles (NPs) (Fe3O4) in films produced from sisal pulp or acetates from this pulp. To obtain composite films with good magnetic properties, as well as mechanical properties similar or better than those of the pure films was also intended. The sisal pulp was chosen due to the fact that the plant is widely produced, not to mention its rapid growth and fibers with a high cellulose concentration. Magnetite was chosen due to its low toxicity when compared with metallic NPs and its potential application in several areas, including the medical area. The magnetite was obtained by thermal decomposition (polyol method) and characterized by transmission and scanning electron microscopy (TEM), X-ray diffraction (XRD) and by SQUID magnetometry (superconducting quantum interference device).The results showed that the prepared NPs correspond to a system of spherical and monodisperse particles with a mean diameter of 5.1 ± 0.5nm and superparamagnetic behavior at room temperature. The films were prepared by dissolving cellulosic pulp (2 g) in dimethylacetamide/lithiumchloride (DMAc/LiCl) to 160°C, with or without NPs (0.5, 1.4 and 3.0 g g L-1) and characterized by electron microscopy (SEM), energy dispersive X-ray spectrum (EDX), XRD, tensile properties and vibrating sample magnetometry (VSM). Results of atomic absorption (Li) and elemental analysis (N) showed that LiCl and DMAc were practically eliminated from the films. Increasing the concentration of magnetite NPs in the composite films made them less rigid, with higher tensile strength and elongation when compared to the cellulose film. The saturation magnetization of the composite films (23, 31, and 37 emu g-1) was positively correlated with the concentration of NPs. The lack of hysteresis and coercivity indicated that the composite films are superparamagnetic at room temperature. Subsequently, cellulose was acetylated in DMAc/LiCl, at 110°C for 4h, and acetates with different degrees of substitution (DS) were obtained. Composite films from these acetates were obtained in DMAc/LiCl (conditions similar to those of the cellulose films) in the absence and presence of NPs (3.0 g L-1).The characterization of these films was performed by XRD, SEM, EDX, TG and DSC, tensile testing and VSM. SEM images showed that acetate films with different DS exhibited different morphologies and that the introduction of NPs in the matrices of different acetates had no effect on the morphology of the films. Films from acetates of DS greater than or equal to 2.0 showed microspheres on its surface. Acetate films more substituted were less resistant to traction than acetate films less substituted and the inclusion of NPs in these matrices led to less rigid films. Overall, composite films exhibited lower levels of crystallinity and thermal decomposition starting at lower temperatures (between 220-270°C) compared to the corresponding acetate film (control) (between 280-300°C), but without compromising the ability of application. The composite films based on cellulose acetate showed superparamagnetic behavior at room temperature with blocking temperature of 14 K and good saturation magnetization (27-46 emu.g-1). No correlation between DS and the magnetic properties of the films was observed, which showed some dependence on the presence or absence of microspheres. The association of the NPs in the polymeric matrices of both cellulose and cellulose acetate led to polymeric films with good magnetic and mechanical properties.

A presença da pirita (FeS2) em depósitos de rejeitos de carvão mineral pode causar danos ambientais. A pirita oxida e proporciona a geração da drenagem ácida de minas (DAM). Uma possível maneira de se evitar tal problema é separando a pirita e empregando-a para algum fim. Assim, o objetivo do presente trabalho foi desenvolver uma rota para sintetizar óxidos magnéticos a partir de um concentrado de pirita oriundo de rejeito de carvão. Experimentalmente, utilizou-se 300 kg de um concentrado com 73,2% de pirita em escala piloto. Realizou-se uma etapa de lixiviação aeróbica com água, em circuito fechado, com o intuito de se obter um extrato aquoso rico em íons férricos. A seguir, procederam-se mudanças no sistema de forma a estabelecer uma condição anaeróbia e redutora ao meio para obterem-se íons ferrosos. O lixiviado, rico em íons Fe2+ e SO4 2-, foi misturado com etanol para a precipitação do ferro como melanterita. Duas rotas para a produção de óxidos ferromagnéticos foram avaliadas. Primeiro, para a síntese de ferritas, utilizou-se o direto ajuste de pH da solução lixiviada reduzida até 10,5 durante 4 dias e posterior precipitação do material magnético. Segundo, para a síntese da magnetita, os cristais de melanterita, obtidos pela precipitação com etanol, foram dissolvidos em água deionizada e procedeu-se o mesmo ajuste de pH e tempo reacional para a cristalização do ferro na forma de óxido. Os cristais foram separados por precipitação, lavados com água deionizada, secos e caracterizados em relação à composição elementar, cristalinidade, distribuição granulométrica, forma, termodecomposição e magnetização. Pode-se concluir que os procedimentos empregados resultaram na obtenção de ferritas e cristais de magnetita na faixa granulométrica entre 0,1 e 10,0 μm. As ferritas apresentaram medidas de magnetização de saturação e coercividade de 29 emu/g e 33,4 Oe e a magnetita de 86,6 emu/g e 75,2 Oe. Os rendimentos em relação ao Fe presentes no lixiviado reduzido (síntese da ferrita de zinco) e melanterita (síntese da magnetita) foram de 34,9% e 93,2%, respectivamente. A produção de reagentes e materiais com valor agregado a partir de concentrados de pirita, oriundo de um rejeito mineral é tecnologicamente viável. O custo estimado para a produção de nano e microgrãos de magnetita foi calculado em R$ 136,29/kg. O processo reduz o desperdício de materiais, minimiza impactos de descarte de resíduos ao meio ambiente e pode tornar-se uma fonte de recursos alternativa dentro da cadeia de produção de carvão. Deve-se ressaltar que os óxidos magnéticos encontram aplicações como pigmentos, em suspensões de meio denso, suporte magnético, agente de contraste em medicina e como material adsorvente. / The presence of pyrite (FeS2) in coal tailings deposits can cause environmental damage. Pyrite oxidizes and generates acid mine drainage (AMD). One possible way to avoid such a problem is by separating the pyrite and employing it for some purpose. Thus, the aim of the present work was to develop a route to synthesize magnetic oxides from a pyrite concentrated from coal rejects. Experimentally, it was carried out in a pilot leaching unit with 300 kg of a pyrite concentrate with of 73.2% FeS2. A step of aerobic leaching with closed circuit water was carried out in order to obtain an aqueous extract rich in ferric ions. Next, changes were made in order to establish an anaerobic and reductive condition in the medium to obtain ferrous ions. The leachate, rich in Fe2+ and SO4 2- ions, was mixtured with different proportions of ethanol to precipitate the iron as melanterite. Two procedures to produce ferromagnetic oxides were investigated. First, for ferrite synthesis, the reduced leachate had the pH adjusted to 10.5 and this condition was kept for a period of 4 days for crystallization of the magnetic material. Second, for magnetite synthesis, melanterite crystals obtained by the precipitation with ethanol (A.P) were dissolved in deionized water and the same pH adjustment and reaction time for the crystallization of the iron as ferrites was carried out. The crystals were separated by precipitation, washed with deionized water, dried, and characterized in relation to elemental composition, crystallinity, particles size distribution, shape, thermo-decomposition, and magnetization. The procedures applied resulted in ferrites and magnetite particles in particle size between 0.1 and 10.0 μm. Ferrite particles presented magnetization saturation and magnetization coercivity of 29 emu/g and 33,4 Oe and magnetite particles of 86.6 emu/g e 75.2 Oe. The yields, from the reduced leachate, were 34.9% for ferrites and 93.2% for magnetite. The production of reagent and materials with aggregate values from pyrite concentrates is viable. The estimated cost for nano and micro particles of magnetite synthesis was estimated in R$ 136.29/kg. The process reduces the waste of materials, minimize the discharge of wastes in the environment and could be source of resource in coal production chain. It should be noted that magnetic oxides find applications as pigments, in dense media suspensions, magnetic support, contrast agent in medicine, and as adsorbent material.

Zinkgruvan is a stratiform Zn-Pb-Ag and Cu sulphide deposit hosted by Paleoproterozoic strata in southern Bergslagen, Sweden. The deposit underwent medium-high grade regional metamorphism during the Svecokarelian orogeny, including partial melting of the host succession. Subordinate zones of semi-massive to massive magnetite and Fe-rich skarns occur in marble stratigraphically below the stratiform Zn-Pb-Ag ore but have so far not been described in detail in the scientific literature. This thesis presents results from detailed geological drill core logging, light optical microscopy (LOM) and scanning electron microscopy (SEM), which have been integrated with results from electron microprobe analysis (FE-EMPA) and whole-rock lithogeochemical analysis to provide a comprehensive description of the magnetite mineralization. Samples from the formerly mined magnetite deposits Västerby, Garpa and Åmme - distal to Zinkgruvan - have also been studied to allow for a comparison. The combined dataset has been used to 1) discuss the genesis of the magnetite mineralizations, including their relationship to base metal sulphide mineralization, and 2) evaluate potential vectors to Zn-Pb-Ag and Cu mineralization based on variations in the magnetite deposits. The semi-massive to massive magnetite, adjacent and associated Fe-rich skarn at Zinkgruvan are located in the stratigraphic upper part of the marble host. Three different varieties of magnetite mineralization can be defined: 1) semi-massive to massive magnetite mineralization in marble, 2) magnetite-bearing veins and 3) retrograde magnetite after olivine. Detailed optical microscopy has revealed a positive spatial correlation between aluminium spinel, apatite, magnetite and graphite. Semi-massive to massive magnetite mineralization at Zinkgruvan is enriched in P2O5, ΣREELa-Lu and Mn relative to a carbonate precursor. A positive correlation exists between P2O5 and ∑REELa-Lu, suggesting apatite and monazite are the primary REE-bearing minerals. The fact that the samples with highest P2O5 and ∑REELa-Lu are all Fe-rich rocks suggest the enrichment of the latter is related to the event which formed the Fe mineralization. Magnetite mineralization from the historic iron mines NW of Zinkgruvan share several key attributes with magnetite mineralization at Zinkgruvan. These include: 1) magnetite is the only iron oxide, 2) lithological and mineralogical similarities, including spatial association with marble, 3) equally high whole-rock Fe content, 4) equally high Mn (1-4 wt.% MnO), 5) equally high Eu anomalies (Eu/Eu* = 1.1- 2.8, avg. 1.75), and 6) local presence of sphalerite mineralization. Bending of the tectonic foliation from c. E-W to NW in the western part of Zinkgruvan suggest these magnetite mineralizations may be located along the same trend as those at Zinkgruvan. The normal calc-silicate mineralogy in Zinkgruvan marble (e.g. diopside, forsterite, phlogopite) can be explained by prograde regional metamorphic reactions between silicates and dolomite or calcite in impure carbonate rocks with a variable content of detrital siliciclastic and volcaniclastic material. However, the stratabound magnetite mineralization and associated Fe-rich skarns cannot be fully accounted for by this model. It is plausible that the Fe-rich skarns can be explained by similar reactions but involving more Fe-rich carbonates (ferrodolomite, ankerite, siderite). In the absence of quartz, siderite is known to thermally decompose into magnetite and graphite at temperatures above 465° C, whereby siderite-rich rocks may have been precursor to the semi-massive to massive magnetite mineralization. A recent genetic model suggests that the ore-forming fluids which formed Zinkgruvan where similar to those which formed McArthur-type SEDEX deposits. The presented results are consistent with this model, since e.g. siderite is a common alteration mineral in alteration envelopes to such deposits. Hence, magnetite mineralization, Zn-Pb-Ag and Cu-ore may all be related to the same pre-metamorphic hydrothermal system. The current genetic model places the magnetite mineralization at Zinkgruvan proximal to a fossil hydrothermal vent zone (the Burkland discontinuity). It is plausible that the magnetite mineralization mined at surface lay along the northern continuation of the Burkland discontinuity. Based on the assumption that the Burkland Cu-mineralization is most proximal and the old iron mines at Åmme are most distal along this structure, variations in whole-rock lithogeochemistry, mineral chemistry and mineralogy have been used to define nine vectors to economic Zn-Pb-Ag and Cu ore as is mined at Zinkgruvan.

Nanoparticulas magnéticas (NPMs) de óxido de ferro tem sido amplamente utilizadas em diversas áreas da biotecnologia e biomedicina, tais como no tratamento de câncer, na entrega controlada de fármacos e como agentes de contraste em imagem por ressonância magnética. O intuito deste trabalho foi sintetizar nanopartículas magnéticas com magnetização de saturação intensificadas via processo do poliol modificado e modificar sua superfície afim de promover a biocompatibilização dos sistemas. Além da funcionalização de nanopartículas previamente biocompatibilizadas utilizando dois métodos: via ligação amida com moléculas de ácido fólico (AF) e com a encapsulação das nanopartículas com quitosana. A modificação de superfície deu-se via procedimentos de lavagem de superfícies, adição e/ou troca de ligantes utilizando moléculas de ácido ?- aminocapróico (EACA), aminopropiltrimetoxisilano (APTMS) e ácido dimercaptosuccínico (DMSA). Através da microscopia eletrônica de transmissão (TEM), foi obtido que as nanopartículas magnéticas de magnetita obtiveram um diâmetro médio de 8 nm, em uma estreita distribuição de tamanho. A difração de raios-X (DRX) indicou a formação de magnetita em todos os sistemas em que o método do poliol modificado foi utilizado. As medidas de espectroscopia vibracional na região do infravermelho (FTIR) evidenciaram a presença de modos de vibração relacionados às macromoléculas e compostos inorgânicos utilizados na modificação de superfície das nanopartículas magnéticas e/ou funcionalização. A TEM das diferentes modificações de superfície mostram a formação de aglomerados dependendo da molécula utilizada. Os estudos de estabilidade coloidal foram necessários para que o meio biológico fosse simulado para uma possível aplicação destes sistemas como carreadores para tratamento via magnetohipertermia ou entrega controlada de NPMs para tratamento de câncer. A nanopartícula recoberta com DMSA apresentou melhores resultados de estabilidade coloidal. Com os sistemas funcionalizados com ácido fólico, o procedimento via ligação com carbodiimida na presença de NHS demonstrou ser eficaz na formação de ligação amida, confirmada por FTIR e quantificação de ligantes. A funcionalização com quitosana necessita de alguns ajustes, visto ser um novo procedimento, porém alguns sistemas em que foi utilizado o método da gelificação iônica possuíram bons resultados de nanocápsulas de quitosana formadas com nanopartículas biocompatibilizadas em seu interior. / Magnetite, iron oxide, is a type of magnetic nanoparticles (NPMs) that is a widely adopted in several areas of biotechnology and biomedicine, such as in the treatment of cancer, controlled delivery of drugs and as contrast agents in magnetic resonance imaging. The purpose of this work is to synthesize magnetic nanoparticles with enhanced saturation magnetization via modified polyol process and modify its surface to promote a biocompatibilization in these systems. In addition, there was the aim to functionalize nanoparticles with modificate surfaces, using two methods: via amide bonding with folic acid molecules (AF) and encapsulation of nanoparticles with chitosan. Surface modification was done via surface washing, addition and / or exchange ligands using ?-aminocaproic acid (EACA), aminopropyltrimethoxysilane (APTMS) and dimercaptosuccinic acid (DMSA) molecules. By transmission electron microscopy (TEM), it was obtained that the magnetite nanoparticles had an average diameter of 8 nm, in a narrow size distribution. X-ray diffraction (XRD) indicated formation of magnetite in all systems where modified polyol method was used. Infrared spectroscopy (FTIR) showed the presence of vibration modes related to macromolecules and inorganic compounds used in the surface modification of magnetic nanoparticles and / or functionalization. The TEM of different surface modifications showed the formation of agglomerates, depending on the molecule used. Colloidal stability studies were necessary to simulate a biological medium for a possible application of these systems as carriers for treatment via magnetohyperthermia or controlled delivery of NPMs for cancer treatment. Nanoparticles coated with DMSA showed better colloidal stability results. With folic acid functionalized systems, the procedure via carbodiimide linkage in the presence of NHS had been shown to be effective in FTIR-confirmed amide bond formation and ligand quantification. The functionalization with chitosan requires some adjustments, since it was a new procedure, however some systems using the ionic gelation method had good results of chitosan nanocapsules formed with biocompatibilized nanoparticles in structure.

For this study, we revisited whether the common iron Fe mineral, magnetite Fe3O4 (s), can reduce tetrachloroethylene (PCE) and trichloroethylene (TCE) as discrepancies exist in the literature regarding rates and extent of reduction. We measured PCE and TCE reduction in batch reactors as a function of magnetite stoichiometry (x = Fe2+/Fe3+ ratio), solids loading, pH, and Fe(II) concentration. Our results show that magnetite reacts only slowly with TCE (t1/2 = 7.6 years) and is not reactive with PCE over 150 days. The addition of aqueous Fe(II) to magnetite suspensions, however, results in slow, but measurable PCE and TCE reduction under some conditions. The solubility of ferrous hydroxide, Fe(OH)2(s), appears to play an important role in whether magnetite reduces PCE and TCE. In addition, we found that Fe(OH)2(s) reduces PCE and TCE at high Fe(II) concentrations as well. At certain conditions degradation of the PCE and TCE is enhanced by an unexplored synergistic response from magnetite and ferrous hydroxide iron phases. Our work suggests that measuring dissolved Fe(II) concentration and pH may be used as indicators to predict whether PCE and TCE will be abiotically degraded by groundwater aquifer solids containing magnetite.

Recently, there has been growing interest in using transition metals (TM) for catalytic and electromagnetic applications, due to the ability of TMs to form stable compounds in multiple oxidation states. In this research, the focus has been on the synthesis and characterization of carbon-supported TM nanoparticles (NPs), specifically palladium (Pd) and gold (Au) NPs, for catalytic applications, and transition metal oxides (TMO) NPs, specifically Fe3O4 NPs for electromagnetic applications. Carbon supports have several advantages, such as enabling even distribution of particles, offering large specific surface area with excellent electron conductivity, and relative chemical inertness. In this dissertation, for catalytic applications, emphasis was on removal of trichloroethylene (TCE) from groundwater. For this application, carbon-supported Pd/Au NP catalysts were developed. Pd was chosen because it is more active, stable and selective for desired end-products, and Au has shown to be a good promotor of Pd's catalytic activity. Often, commercially available Pd-based catalysts are made using harsh chemicals, which can be harmful to the environment. Here, an environmentally friendly process with aspects of green chemistry was developed to produce carbon-supported Pd/Au NP catalysts. This process uses a combination of sonochemistry and solvothermal syntheses. The carefully designed carbon-supported Pd/Au NP catalyst material was systematically characterized, tested against TCE, and optimized for increased rate of removal of TCE. Electron microscopy and spectroscopy techniques were used to study the material including structure, configuration and oxidative state. The Pd/Au NPs were found mainly to form clusters with an aggregate-PdShellAuCore structure. Using state-of-the-art direct detection with electron energy loss spectroscopy, the Pd NPs were found to have an oxidative state of zero (0). The formation of the catalyst material was studied in detail by varying several synthesis parameters including type of solvent, sonication time, synthesis temperature etc. The most optimized catalyst was found remove TCE at double the rate of corresponding commercial Pd-based catalysts in a hydrogen headspace. This material was found to catalyze the removal of TCE via traditional hydrodehalogenation and shows promise for the removal of other contaminants such as trichloropropane (TCP), carbon tetrachloride (CT). This green approach to make and optimize TM materials for specific applications was extended to TMOs, specifically magnetite (Fe3O4) and further developed for the application of electromagnetism. As catalysts, Fe3O4 is used for removal of p-nitrophenol from water. However, since the carbon-supported Pd/Au material system was developed and optimized for catalysis, here, carbon-supported Fe3O4 NPs were developed for electromagnetic applications. There has been growing interest in tuning the magnetic properties of materials at room temperature with the use of external electric fields, for long-term applications in data storage and spintronic devices. While a complete reversible change of material properties has not yet been achieved, some success in partial switching has been achieved using multiferroic spinel structures such as Fe3O4. These materials experience a change in magnetic moment at room temperature when exposed to the electric fields generated by electrochemical cells such as lithium ion batteries (LIBs) and supercapacitors (SC). In the past, a 1% reversible change was observed in Fe3O4 using LIBs. Here, building on the developments from previous material system, Fe3O4 NPs were directly hybridized onto the graphene support in order to increase the observable change in magnetic moment. The material was systematically designed and tested for this application, including a study of the material formation. A simple, environmentally friendly synthesis using the solvothermal process was implemented to make the graphene-supported Fe3O4 NPs. This new material was found to produce a reversible change of up to 18% in a LIB. In order to overcome some of the difficulties of testing with a LIB, a corresponding hybrid SC was designed, built and calibrated. The graphene-supported Fe3O4 NPs were found to produce a net 2% reversibility in the SC, which has not been reported before. The results from both the LIB and SC were analyzed to better understand the mechanism of switching in a spinel ferrite such as Fe3O4, which can help optimize the material for future applications. The focus of this dissertation was on the development of a methodology for carbon-supported TM and TMO NPs for specific applications. It is envisioned that this approach and strategy will contribute towards the future optimization of similar material systems for a multitude of applications.