The isolation of deoxyribonucleic acid (DNA) was studied in the diploma thesis by using three different methods: phenol extraction, salting with sodium chloride and magnetic separation with reversible adsorption of nucleic acids on different magnetic carriers. There were used five different properly functionalized carriers for the isolation of DNA: magnetic silicagel, P(HEMA-co-GMA) ox. I, P(HEMA-co-GMA) ox. II, Dynal DNA Direct and Perovskit 439. The reversible imobilization of DNA on the magnetic carrier was proceeded under the conditions of high concentration of NaCl and poly(ethyleneglycol) (PEG). There was induced the condensation of DNA by 2 M NaCl and PEG with molecular mass 6000 for binding of the DNA to the magnetic carriers and the final concentration of PEG in the separation mixture was 8 and 16 %. The aim was to gain the DNA of quality suitable for polymerase chain reaction (PCR). The DNA was isolated from the bacterial cultures of three probiotic strains, L. amylovorus CCM 4380T, L. zeae CCM 7069 T, L. plantarum CCM 7039T, which were cultivated in MRS medium. The DNA was also isolated from the fermented dairy products: Jihočeský zákys s ovocem jahoda (the fermented dairy product with the probiotic culture of Lactobacillus acidophilus, Bifidobacterium lactis and Streptococcus thermophilus), Revital active (the yogurt with inulin and the probiotic culture of Lactobacillus rhamnosus, Lactobacillus acidophilus and Bifidobacterium sp.) and Actimel višeň (the dairy product with the probiotic culture of Lactobacillus casei). When the PCR with the isolated DNA was passed off, the PCR products were detected by the gel electrophoresis with agarose. The success of the DNA isolation of the probiotic bacteria by phenol extraction, salting with NaCl and by magnetic separation, was verified by the PCR method. The method of magnetic separation using magnetic carriers was also verified for the isolation of DNA of quality suitable for PCR from the probiotic fermented dairy products.

Depuis deux dernières décennies, la séparation magnétique revient sur le tapis grâce aux applications biomédicales émergentes à la séparation de cellules ou de protéines et aux tests immunologiques. Cette thèse porte sur l’exploration détaillée de la séparation magnétique de nanoparticules à l’échelle microfluidique, amplifiée par la séparation de phase induite par le champ. Dans ce but, nous synthétisons des nanoclusters superparamagnétiques d’oxyde de fer de taille 40-70 nm, composés de nanoparticules de taille 7-9 nm. Nous faisons une étude détaillée de la cinétique de la séparation de phase de ces nanoclusters induite par le champ ainsi que de leur séparation magnétique dans des canaux microfluidiques munis de réseaux ordonnés de micropiliers magnétisables. Le taux d’agrégation de nanoclusters est principalement régi par le paramètre du couplage dipolaire et par la fraction volumique de nanoclusters, tandis que l’efficacité de capture – par le nombre de Mason. Les couches de molécules adsorbées sur la surface de nanoclusters d’habitude affaiblissent les interactions magnétiques et diminuent l’efficacité de capture, cependant, dans certains cas, elles peuvent induire des interactions colloïdales attractives et augmenter l’efficacité de capture. Les résultats de ce travail peuvent être utiles pour le développement des tests immunologiques magnéto-microfluidiques. / Magnetic separation has been gaining a new interest during two last decades thanks to emerging biomedical applications to cell or protein separation and immunoassays. This thesis is aimed at detailed exploration of magnetic nanoparticle separation in microfluidic scale enhanced by field-induce phase separation of nanoparticles. To this purpose, we synthesize superparamagnetic iron oxide nanoclusters of a size of 40-70 nm composed of numerous nanoparticles of a size 7-9 nm. We perform a detailed study of the kinetics of the field-induced phase separation of these nanoclusters as well as of their magnetic separation in microfluidic channels equipped with ordered arrays of magnetizable micropillars. The nanocluster aggregation rate is mostly governed by the dipolar coupling parameter and the nanocluster volume fraction, while the capture efficiency – by the Mason number. Molecular layers adsorbed on the nanocluster surface usually weaken magnetic interactions and decrease the capture efficiency, however, in some casesthey may induce attractive colloidal interactions and enhance the capture efficiency. The results of this work could be useful for development of magnetomicrofluidic immunoassays.

La séparation magnétique est utilisée dans le domaine de la purification de l’eau. Des nanoparticules magnétiques fonctionnalisées ou nues sont en charge de capter un polluant ciblé puis sont enlevées de l’eau par l’application d’un champ magnétique. Nous avons montré que l’utilisation d’un ferrofluide aqueux classique constitué de nanoparticules d’oxyde de fer recouvertes par une double couche de surfactant d’acide oléique permet une adsorption efficace des cations métalliques (ion nickel Ni2+) puis leur enlèvement en utilisant des microparticules magnétiques. Nous avons montré que des interactions magnétiques suffisamment fortes entre les nanoparticules induisent une transition de phase colloïdale. Il existe trois régimes de captage qui dépendent de deux paramètres, le premier paramètre est lié à l’intensité du champ magnétique et le second est la concentration en nanoparticules. En présence de l’écoulement de la suspension des nanoparticules, le captage des nanoparticules est toujours régi par la concentration en nanoparticules et également par le nombre de Mason. Nous avons mené une expérience de captage des nanoparticules par un milieu poreux. L’efficacité de filtration est liée à la compétition entre les forces hydrodynamiques et magnétiques ainsi que de la séparation de phase au sein de la suspension. Les théories développées lors de ce travail sont en accord raisonnable avec les résultats expérimentaux et montrent l’augmentation de l’efficacité de captage des nanoparticules avec l’augmentation de l’intensité du champ magnétique et de la concentration en nanoparticules ainsi que la diminution de l’efficacité de captage avec l’augmentation du nombre de Mason. / Magnetic separation is used in the domain of water purification. In these systems, functionalized or bare magnetic nanoparticles are used to capture a target pollutant then they are extracted from water by an applied magnetic field. We have shown that a classical aqueous ferrofluid composed by iron oxide nanoparticles covered with an oleic acid double layer allows efficient adsorption of metallic cations (nickel ion Ni2+) followed by nanoparticle extraction with the help of magnetic microparticles. We have shown that strong enough magnetic interactions between nanoparticles can induce a colloidal phase transition. There exists three capture regimes which depend on two parameters, the first one is related to the magnetic field intensity and the second is the nanoparticle concentration. In the presence of the flow of nanoparticle suspension, the nanoparticle capture is always governed by the nanoparticle concentration and also by Mason number. We have carried out an experiment on nanoparticle capture in a porous medium. The filtration efficiency is related to the competition between the hydrodynamic and magnetic forces, as well as to the phase separation in the suspension bulk. The theories developed in the frames of this work show a reasonable agreement with the experimental results. They predict an increase of the capture efficiency with an increase of the magnetic field intensity and the nanoparticle concentration as well as a decrease of the capture efficiency with the growth of the Mason number.

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Bringing together several materials into a single nanoparticle is an attractive way to design systems that exhibit diverse physical and chemical properties. Cobalt nanoparticles are extensively used in magnetic separation, ferrofluids, and magnetic storage media. The deposition of gold nanoparticles onto cobalt core significantly affects their optical properties due to the introduction of surface Plasmon. Here the synthesis of gold nanoparticles decorated cobalt-silica nanoparticles are reported for the first time. Their optical and magnetic properties and capacity as a surface enhanced Raman scattering (SERS) substrate were investigated. This nano-material is of particular interest as a dual agent allowing both magnetic separation and SERS detection. The synthesis involves three steps: i) synthesis of Co nanoparticles / ii) deposition of a silica shell around the Co core and introduction of amine functional groups on the surface / iii) decoration of the surface with gold nanoparticles. Co nanoparticles were prepared in an inert atmosphere in the presence of capping and reducing agents. Size of the cobalt nanoparticles was varied by changing the concentration of the capping agent. Since cobalt particles are easily oxidized, they were coated with silica shell both to prevent oxidation and allow further functionalization. Silica coating of the particles were performed in water/ethanolic solution of tetraethyl orthosilicate (TEOS). Thickness of silica coating was controlled by varying the concentrations of TEOS. Besides, by adding 3-aminopropyl-triethoxysilane (APTS) to the reaction medium, primarily amine groups were introduced on the silica surface. For further modifications citrate stabilized gold nanoparticles were appended onto the surface of amine modified core-shell cobalt-silica nanoparticles. Gold decorated magnetic core-shell structures were used as SERS substrate with Raman dyes / brilliant cresyl blue (BCB) and rhodamine 6G (R6G). They were also utilized for preconcentration and SERS detection of 4-mercapto benzoic acid (4-MBA). Gold nanoparticles on the silica and thiol group on the 4-MBA were very selective to each other, thus, 4-MBA could be attached on to gold surface and it could be easily separated magnetically from the reaction medium and identified by Raman spectroscopy. Characterization of the cobalt, cobalt-silica and gold modified cobalt-silica nanoparticles was done by Field Emission Scanning Electron Microscopy (FE-SEM), Scanning-Transmission Electron Microscopy (S-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), UV-Vis spectrometry, and Raman microscope system.

Submitted by Stéfany Moreira (stemellra@yahoo.com.br) on 2013-02-25T12:57:59Z No. of bitstreams: 1 DISSERTAÇÃO_AproveitamentoMinériosFerro.pdf: 4941141 bytes, checksum: 7fc54169ae9d05ca62dad2964a3d2b36 (MD5) / Approved for entry into archive by Neide Nativa (neide@sisbin.ufop.br) on 2013-02-25T14:03:40Z (GMT) No. of bitstreams: 1 DISSERTAÇÃO_AproveitamentoMinériosFerro.pdf: 4941141 bytes, checksum: 7fc54169ae9d05ca62dad2964a3d2b36 (MD5) / Made available in DSpace on 2013-02-25T14:03:40Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO_AproveitamentoMinériosFerro.pdf: 4941141 bytes, checksum: 7fc54169ae9d05ca62dad2964a3d2b36 (MD5) Previous issue date: 2012 / Essa dissertação descreve a situação atual e as tendências relacionadas ao tratamento de minérios de ferro de baixo teor na indústria mineral, utilizando um estudo de caso e uma discussão sobre o projeto de implantação de uma instalação de tratamento de itabiritos de baixo teor, denominada ITM-S, a ser instalada em uma empresa mineradora de ferro no Estado de Minas Gerais. Seu objetivo principal foi analisar a viabilidade técnica e econômico-financeira desse projeto, com base nos conceitos existentes na metodologia FEL (Front-End-Loading), associados aos conceitos de sequenciamento de lavra, beneficiamento mineral e economia mineral. Foram analisados, na metodologia, dois cenários do projeto para a escolha das alternativas de rotas de processo: com o uso de separação magnética (cenário 1), e sem a utilização de separação magnética (cenário 2). Os resultados mostraram que o cenário 2 é o mais viável economicamente, devido principalmente a redução do investimento por tonelada produzida, dentre outros fatores. Pretende-se apresentar as várias evoluções nos processos de tratamento de minério de ferro, e apresentar uma metodologia adequada para análise de viabilidade de projetos de tratamento e aproveitamento de minérios de ferro marginais, como a metodologia FEL, associada aos conceitos existentes na engenharia de minas. ____________________________________________________________________________________________________ / ABSTRACT: This dissertation describes the current situation and trends related to the exploitation of low-grade iron ore in the mineral industry, to accomplish it, a case study and a discussion on the implementation project of a treatment facility for low grade itabirites called ITM-S, to be installed in an iron ore mining company in the State of Minas Gerais, are presented. The main objective was to analyze the technical and economic-financial feasibility of this project, based on FEL methodology (Front-End- Loading) existing concepts, associated with the mining concepts of sequencing, mineral processing and mineral economics. Using this methodology, two project’s scenarios were analyzed in order to help to choose between two alternative routes: magnetic separation usage (scenario 1), and no usage of magnetic separation (scenario 2). The results showed that scenario 2 is the most economically viable; mainly due to reduction of the investment per ton produced, among other factors. This work intends to present the various evolutions in the iron ore treatment processes, and to present an appropriate methodology for marginal iron ore project feasibility analysis, such as the FEL methodology, associated with the existing concepts in mining engineering.

Dans le cadre de ce travail de thèse, la polymérisation de type RAFT a été exploitée pour synthétiser des particules de latex magnétiques décorées de polymères stimulables. Cinq (co)polymères hydrophiles ont tout d'abord été préparés via la (co)polymérisation RAFT en solution d'acide acrylique (AA) et de méthacrylate de 2-diméthylaminoéthyle (MADAME). Les agents macromoléculaires obtenus (macroRAFT) : des homopolymères de PAA ou PMADAME ainsi que des copolymères P(AA-co-MADAME), présentent une sensibilité au pH et à la température. Ces macroRAFT hydrophiles ont ensuite été utilisés dans des réactions d’extension de chaîne avec du styrène conduisant à la formation de copolymères à blocs amphiphiles bien définis. Puis, des dispersions aqueuses d’agrégats (clusters) de nanoparticules d’oxyde de fer (OF) ont ensuite été préparées via un procédé de mini-émulsification/évaporation de solvant, en utilisant les copolymères à blocs comme stabilisants. Après optimisation des conditions expérimentales (sonication, concentration de macroRAFT, pH), des agrégats de taille contrôlée (45 à 300 nm) ont pu être obtenus. Ces clusters ont ensuite été utilisés comme semence lors de la polymérisation en émulsion du styrène, conduite en présence d’un agent de réticulation. Les clusters d'OF ont été individuellement encapsulés par une couche de polymère, formant des particules magnétiques stabilisées par le segment hydrophile des copolymères à blocs. Enfin, les particules magnétiques décorées de copolymères de P(AA-co-MADAME) ont été utilisées avec succès pour la capture et le relargage de bactéries grâce à la modulation de leurs propriétés de surface en fonction du pH / In this work reversible addition-fragmentation chain transfer (RAFT) polymerization was exploited to synthesize magnetic latex particles decorated with stimuli-responsive polymer brushes. First, five hydrophilic (co)polymers with various compositions were successfully prepared by RAFT solution (co)polymerization of acrylic acid (AA) and 2-dimethylaminoethyl methacrylate (DMAEMA) for different AA to DMAEMA molar ratios. The obtained macromolecular RAFT agents (macroRAFTs), PAA or PDMAEMA homopolymers and P(AA-co-DMAEMA) copolymers, displayed interesting pH- and thermo-responsive properties. These hydrophilic macroRAFTs were then chain extended with styrene leading to the formation of well-defined amphiphilic block copolymers. An aqueous dispersion of iron oxide clusters was next prepared using a strategy based on emulsification/solvent evaporation in which the block copolymers were used as stabilizers. By varying the experimental conditions (sonication power, macroRAFT concentration and pH of the medium), the cluster size could be controlled from 45 up to 300 nm. These clusters were then used as seeds in styrene emulsion polymerization in the presence of a crosslinker. The iron oxide clusters were individually encapsulated into a polymer shell generating latex particles, stabilized by the hydrophilic segment of the block copolymers, and displaying interesting magnetic properties. At last, these magnetic beads were evaluated as carriers in the magnetic separation of bacteria. The magnetic latex particles decorated with P(AA-co-DMAEMA) copolymers were successfully employed for the capture and trigger release of bacteria, allowing their concentration in a biological sample

Zinkgruvan is a Pb-Zn-Ag deposit located in south-central Sweden, owned and operated by Lundin Mining. The ore is beneficiated by a collective-selective flotation circuit, recovering both galena and sphalerite in a bulk rougher-scavenger flotation stage and later on separating them into two final products. Opportunities for increase in zinc recovery in the bulk rougher scavenger flotation stage have been identified as the plant is relying on natural Pb-activation to process the ore. Process mineralogical tools were used to characterize four different orebodies from Zinkgruvan (Burkland, Borta Bakom, Nygruvan and Sävsjön) and evaluate the metallurgical performance for flotation and magnetic separation, following a geometallurgical approach to better understand and predict the behavior of such ore types in processing plant. The first hypothesis in this thesis is that by addition of copper sulfate and increased collector dosage, Zn recovery will be improved without being detrimental to galena flotation. Results demonstrated that there is a significant increase in Zn recovery by further increasing collector dosage and copper-activating the flotation pulp in the scavenger stage. For instance, an increase in zinc recovery up to 16% has been achieved after addition of copper sulfate. Galena is readily floatable while sphalerite takes longer to be recovered. In addition, iron sulfides take longer to be recovered and, after addition of copper sulfate, there was an increase in iron sulfide recovery. The amount of iron sulfides reporting to the concentrate should still not be a problem to the plant. Most of the Fe in the concentrate is still coming from the sphalerite lattice. However, it might be that some orebodies coming into production in the near future have higher amounts of pyrrhotite, which might be a problem. Therefore, magnetic separation methods have been tested to remove pyrrhotite from the bulk ore. The second hypothesis is that the high Fe content in the concentrate might be due to the presence of iron sulfides, in which case they could be selectively removed by magnetic separation. XRD analyses demonstrated that Sävsjön is a highly variable orebody, and that its high Fe content varies with the location inside the orebody, being caused by either iron sulfide or iron oxide minerals. Both monoclinic and hexagonal pyrrhotite have been observed. Davis Tube could remove monoclinic pyrrhotite but it was very inefficient when dealing with hexagonal pyrrhotite. WHIMS, on the other hand, performed well for both types of pyrrhotite. When applying Davis Tube on Sävsjön OLD feed, a concentrate with up to 52.3% pyrrhotite is achieved, at a recovery of 35.32%. However, sphalerite is also reporting to the magnetic concentrate, which would generate Zn losses for the overall process. Zinc losses were up to 15.3% when the highest field strength was applied. Therefore, the applicability of magnetic separation for Zinkgruvan ore must be further evaluated.