The thermodynamic history of the Earth is preserved in the trace element record created through igneous processes. The ability to interpret that record depends on the accuracy and precision of numerical models that connect igneous processes with their geochemical consequences. This project answers three major questions concerning the relationship between trace element partitioning and the processes that influence it. One: using a common igneous mineral, clinopyroxene, as a base, how complete is the dataset on which our understanding of this relationship relies? Two: what are the dangers involved with basing models on experiments that contain higher than natural concentrations of trace elements? Three: how accurate and precise is the current numerical model that describes this relationship, and can it be improved? This project determined that the data contain gaps at high pressures and temperatures, are limited for felsic rock compositions, and are lacking for hydrous conditions. A set of experiments conducted on plagioclase feldspar crystallization from a base MORB composition containing various levels of dopants at below wt% levels reveals the presence of non-Henry's Law partitioning behavior through the disruption of the phase equilibria of the system. Lastly, the current clinopyroxene/melt rare earth element partitioning model (Wood and Blundy, 2003) is shown to reasonably, though less than ideally, describe the relationship between igneous processes and their trace-element partitioning results using the thermodynamics of the system. The accuracy was improved through adding a regression, which is based on the major element concentrations of the clinopyroxene and melt to the original numerical expressions. / Graduation date: 2012

It is important to understand the processes that influence the critical zone (CZ) evolution to ensure its sustainability. This thesis reports on laboratory and field experiments designed to measure the behavior of biogenic and lithogenic chemical species and their interaction in the CZ from column to pedon to catchment scales. We postulated that interactions between organic matter and rock-derived metals drive coupled processes of carbon stabilization and chemical weathering and denudation in the Jemez River Basin Critical Zone Observatory (JRB-CZO). First, we observed that secondary mineral coatings (Al and Fe (oxy)hydroxides) on primary silicate surfaces play a major role in sequestering aromatic and "humified" dissolved organic matter (DOM) into sorbate form, significantly retarding their subsurface transport. Further, reinfusion to OM-reacted-porous-media of a different DOM source resulted in exchange reactions consistent with a zonal model of OM adsorption at mineral surfaces. This dissertation also aimed to examine the influence of water and DOM fluxes on the CZ weathering processes. Rare earth elements (REE) were selected because of their coherent trends in reactivity toward organic ligands common to soils. Specifically, trends in REE fractionation were explored for their utility to inform on biogeochemical weathering processes in forested terrain in the JRB-CZO. Mineral weathering mechanisms are expected to differentially influence REE release, fractionation, and transport and the relative importance of such processes should be reflected in REE signatures of bulk soil, pore and surface waters. Our studies showed: (1) REE depletion trends with depth in bulk soils are correlated with topographically-induced variation in water and dissolved organic carbon (DOC) flux (reflected in negative correlations between total water and C fluxes) and solid phase REE concentrations measured at the same depths; (2) REE and DOC concentrations in stream waters were strongly correlated during snowmelt periods of high discharge, consistent with REE complexation and mobilization in association with organic ligands during shallow subsurface flow; (3) preferential sequestration of Eu occurs during formation of secondary Mn(IV)-oxides, explaining patterns of Eu enrichment in bulk soils; and (4) the incremental increase in positive Ce-anomalies with depth in bulk soils are apparently controlled by adsorption/co-precipitation with secondary Fe-(oxy)hydroxide minerals.

The redox-sensitive geochemical behavior of uranium permits the use of Th/U ratios as a geochemical proxy for the oxidation state of the atmosphere and oceans during sedimentary processes. Due to the effects of post-depositional uranium mobility on Th/U ratios during events involving oxygenated fluids, direct measurements of Th/U ratios are often misleading, but the whole rock Pb isotope composition may be used to determine a sample¡¦s apparent time-integrated Th/U ratio (ƒÛa) and the timing associated with the onset of the U-Th-Pb geochemistry. Rare earth element (REE) concentrations were determined by isotope dilution mass spectrometry to evaluate the influence of multiple provenance components and potential mobility of Th, U, and Pb during post-depositional processes on the Th/U ratio. The Pb isotope compositions and REE concentrations were determined for six Paleoproterozoic sedimentary sequences, which were the focus of previous studies involving the timing of the rise of atmospheric oxygen. The Mount McRae Shale, Huronian Supergroup, and Zaonezhskaya Formation have been interpreted as experiencing post-depositional alteration (perhaps associated with orogenic events) due to Pb-Pb ages that are younger than the likely depositional age and observed fractionation of REE in chondrite normalized REE patterns and interelement REE ratios (e.g. La/Nd, La/Yb, Eu/Eu*). Similar geochemical proxies have been interpreted as sedimentary geochemical features of the Timeball Hill Formation, Hotazel Formation, and Sengoma Argillite Formation. This study of Paleoproterozoic sedimentary units constrains the onset of U-Th decoupling, most likely due to the onset of oxidative weathering conditions, began by 2.32 Ga, the latest.

Research in the field of non-linear optical (NLO) devices lead to an increasing interest in new borate compounds, capable of expanding the frequency range provided by common laser sources. Lithium triborate (LBO) is a newly developed ideal non-linear optical crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. Borates containing rare-earth elements are of great interest since they are found to be superior in non-linear optical applications. In this study, synthesis and identification of rare-earth doped lithium triborate was carried out. Lithium triborate was produced from the solid-state reaction. LBO was then doped with some rare-earth elements (Gd, La, Y) in several different concentrations. Appropriate quantities of Li2CO3 and H3BO3, weighted separately, were mixed and finely powdered. Then, the mixture was heated at 750 &ordm / C for 14 hrs. The expected reaction is given below. Li2CO3 + 6H3BO3 --&gt / 2LiB3O5 + CO2 + 9H2O Prepared LiB3O5 and Gd2O3, La2O3 and Y2O3 samples were weighed separately at different concentrations and ground together. The mixture was then heated at 750 &ordm / C for 7 hrs. Characterization of the new products was done by X-Ray Diffraction (XRD) and Infrared (IR) analysis. Differential Thermal Analysis (DTA) was used for examination of the thermal properties of the compounds, morphology of new compounds was observed by Scanning Electron Microscopy (SEM). The compounds are then subjected to thermoluminescence (TL) studies. From the XRD studies, no change in the LBO phase related to the addition of rareearth elements was observed. However, peaks of those elements were also become apparent. IR analysis showed that there is no change related to B-O link with the addition of rare earth elements. DTA studies showed that the melting point of LBO decreases with the addition of rare earth elements. In the SEM images, two phases belonging to particles of rare earth elements and lithium triborate were observed clearly. With the TL analysis, it was considered that the samples show dose response but also it was realized that they are affected by fading.

This thesis analyses EU policy making on critical metals for renewable energy technologies, with a focus on Rare Earth Elements (REEs) and cobalt. A thematic text analysis on EU documents published between 2010-2018 was conducted to identify themes and patterns in the EU debate and policy-making. The results showed that the EU has a clear objective to secure access to critical metals, to reduce import dependency and increase competitiveness on the market for critical metals. The key strategies to secure access to metals are to increase primary supply by increased domestic mining and by investing in countries with large reserves of critical metals; to improve recycling rates of these metals; to find substitution metals to replace the critical ones; and to focus on resource diplomacy. Environmental and social risks from an increased demand for REEs and cobalt gain little attention in the studied documents. Geopolitical risks are concluded as linked to the dependency on import from a few producing countries, China for REEs and DR Congo for cobalt, and are mainly focused on risks affecting the EU access to the metals. The struggle over resources and related geopolitical interactions are concluded to be affected by historical and existing global power structures. Further, the thesis concludes that EU resource diplomacy aims at facilitating for the EU to remain a powerful and competitive actor on the global market for trade of critical metal.

En raison du risque d’un approvisionnement insuffisant en ressources primaires des terres rares et des impacts environnementaux générés par les zones minières, le concept de l’agromine paraît être une solution très prometteuse. Il permet d’extraire des métaux lourds à partir de sols pollués ou de friches industrielles, par une méthode respectueuse de l’environnement, grâce à la culture de plantes hyperaccumulatrices. Une fois la culture réalisée, des procédés hydrométallurgiques sont développés afin d’extraire des plantes les métaux ayant une valeur économique importante. Le présent travail vise à développer des procédés hydrométallurgiques pour l’extraction des terres rares à partir d’une plante hyperaccumulatrice appelée Dicranopteris dichotoma. Cette fougère est connue pour sa capacité à accumuler les terres rares, notamment les légères, dans sa partie aérienne. Différentes voies d’extraction, puis de séparation des terres rares des autres éléments, ont été étudiées. Dans un premier temps, des lixiviations de la biomasse sèche ont été mises en oeuvre. Les rendements de lixiviation selon la nature de l’extractant ont ainsi pu être comparés. Pour cette voie, une précipitation est ensuite effectuée, suivie d’une calcination pour obtenir les oxydes de terres rares. Dans un second temps, la lixiviation de la biomasse sèche a été intensifiée par un procédé d’échange d’ions au cours duquel les terres rares sont fixées sur la résine. Après avoir percolé sur la résine des solutions qui permettent d’éliminer des impuretés, l’élution permet d’obtenir une solution concentrée de terres rares. Enfin, une troisième voie d’extraction est réalisée à partir des cendres de D. dichotoma, après une étape de combustion. Cette voie repose sur une lixiviation alcaline des cendres permettant l’élimination des impuretés solubles dans ce milieu. Une dissolution du résidu est ensuite effectuée, suivie d’une précipitation sélective des terres rares. Les trois voies étudiées s’avèrent en fait complémentaires et la combinaison de certaines étapes peut s’avérer prometteuse, notamment pour éliminer certaines impuretés. L’étude de ces procédés et de leur combinaison mérite d’être poursuivie afin d’améliorer les rendements d’extraction et la pureté du produit final. Il s’agira ensuite de développer un procédé à l’échelle pilote puis industrielle / Due to the risk of primary resource supply of rare earths and the environmental impacts generated by mining areas, the concept of agromining seems to be a very promising solution. It allows the extraction of heavy metals from polluted soils or industrial wastelands, by an environmentally friendly method, thanks to the cultivation of hyperaccumulating plants. Once the culture is completed, hydrometallurgical processes are developed in order to extract from plants the metals having a significant economic value. The present work aims to develop hydrometallurgical processes for the extraction of rare earths from a hyperaccumulator plant called Dicranopteris dichotoma. This fern is known for its high ability to accumulate rare earths, especially light ones, in its aerial part. Different extraction and separation ways of rare earths from other elements have been studied. At first, leaching of dry biomass was implemented. The leaching yields according to the nature of extracting solutions could thus be compared. For this approach, precipitation is then performed, followed by calcination step to obtain rare earth oxides. In a second approach, the leaching of dry biomass was intensified by an ion exchange process during which, the rare earths are fixed on the resin. After percolating solutions on the resin in order to eliminate impurities, an elution step leads to obtain a concentrated solution of rare earths. Finally, a third extraction process is carried out from the ashes of D. dichotoma, after a combustion step. This approach is based on an alkaline leaching of the ash allowing the elimination of soluble impurities in this medium. The residue is then dissolved, followed by rare earths selective precipitation. These three approaches studied, are actually complementary and the combination of certain steps can be promising, especially to eliminate some impurities. The study of these processes and their combination deserves to be pursued in order to improve the extraction yields and the purity of final product. It will then develop a pilot scale and industrial process

Nós estudamos o controle estrutural dos veios de pegmatitos graníticos (tipo F-ETR-Li) associados à fácies albita granito (AEG) do granito Madeira (~1.83Ga). Esta fácies corresponde ao depósito, de classe mundial, de Sn-Nb-Ta-F (criolita) da mina de Pitinga. Atualmente, esses pegmatitos ricos em ETR (xenotima e gagarinita) são explorados junto com o minério disseminado, porém possuem potencial para exploração por lavra seletiva. Todos os pegmatitos possuem arranjo geométrico e mineralogia similares, o que sugere mesma fonte. Também possuem mineralogia igual à da encaixante e seu alojamento ocorreu na própria rocha parental. O arranjo geométrico dos pegmatitos foi controlado por estruturas contracionais frágeis (falhas inversas, leques de imbricação e cavalos). Os planos de falhas inversas (N320/60SW) serviram como condutos para o fluido que se alojou preferencialmente em fraturas horizontais distensivas. O arranjo geométrico bem definido dessas estruturas e o fato de que também há planos de falhas inversas sem pegmatitos demonstram que as fraturas que hospedam os pegmatitos não foram formadas pela pressão do fluido. A orientação das estruturas contracionais no AEG indica que ocorreu um transporte de SW para NE. Como este corpo possui pequena dimensão, resfriou-se rapidamente. Contudo, sua localização na crosta superior fria e a baixa temperatura solidus permitiram a formação dos pegmatitos. No nível estrutural em que se encontram os pegmatitos estudados, quando esses veios se alojaram, o AEG estava cristalizado e posicionado acima da profundidade crustal crítica, onde o estresse normal mínimo é vertical. / We study the structural control of pegmatites (F-REE-Li vein-type granite pegmatite) associated to the albite-enriched granite facies (AEG) of the Madeira A-type granite (~1.83 Ga). This facies corresponds to the Madeira world-class Sn-Nb-Ta-F (cryolite) deposit at the Pitinga mine. These REE-rich pegmatites (xenotime and gagarinite), presently exploited together with the disseminated ore, have potential to explotation by selective mining. They have a common geometric arrangement and share a same mineralogy, therefore they all originate from the same source. They have the same mineralogical composition of the host rock and their emplacement occurred in the parental rock itself. The geometric arrangement of the pegmatites is settled by contractional brittle structures (reverse faults, imbrication fans and horses). The reverse fault planes (~N320/60SW) were essentially the conduits for the fluid. The preferential sites for the pegmatites bodies were the horizontal tensile fractures. The well-marked geometric arrangement of the tectonic structures and the fact that there are also reverse faults planes without pegmatites show that the fractures that host the pegmatites were not formed by the fluid pressure. The orientation of the contractional structures in the AEG indicates a transport from SW to NE. With reduced surface dimensions, the AEG cooled fast, however its location in the cold upper crust and the low solidus temperature allowed pegmatites formation. At the structural level of the studied pegmatites, when these veins positioned, the AEG was crystallized in a position above the critical crustal depth, where minimum normal stress is vertical.

Philosophiae Doctor - PhD (Chemistry) / Rare earth elements (REEs) have widespread use and importance for industrial applications due to their metallurgical, optical and electronic properties. Several typical hydrometallurgical techniques such as adsorption, chemical precipitation, filtration, ion exchange and solvent extraction techniques have been used for separation and recovery of the rare earth metals from aqueous solutions. Adsorption was recognised as one of the most promising methods due to its simplicity, high efficiency and availability. Many adsorbents are being investigated but there are few adsorbents containing specific functional groups in practical use for REEs recovery. This aim of this study was to develop a nanofibre based adsorbent containing glycolic acid functional groups for the recovery of rare earth metals. Polystyrene (PS) and polyethylene terephthalate (PET) nanofibres were prepared by the electrospinning technique, glycolic acid functional groups were grafted onto the PS or PET nanofibres and the potential of the two modified nanofibre adsorbents for adsorption of Ce3+ or Nd3+ from aqueous solution were investigated and compared. The adsorption experiments were carried out to investigate the effect of different adsorption parameters such as pH, contact time and initial concentration in a batch system in order to achieve the objectives of this research.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Gadolinium (Gd) is the basis of contrast media most used in magnetic resonance imaging (MRI). Because it is a very toxic metal ion, all Gd-based contrast media present chelating agents in their composition. Gd-based formulations are commercially available in concentrations of 1 and 0.5 mol L-1, which are almost exclusively excreted by the kidneys without producing toxic effects. In 2006, however, two European groups independently suggested a link between the administration of gadolinium chelates and the occurrence of nephrogenic systemic fibrosis (NSF) in patients with renal insufficiency. NSF is a serious disease, which origin is attributed to transmetalation reactions between Gd and endogenous metals. In this work, we used the techniques atomic absorption spectrometry, mass spectrometry with inductively coupled plasma and liquid chromatography with mass detector to investigate metals present as impurities and / or contaminants in five Gd-based contrast formulations and their possible transmetalation reactions. The results showed that several metals are present in the formulations, the rare earth elements (Sc, Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er and Tm) and others such as Al, As and Pb, notoriously toxic to humans. To evaluate transmetallation reactions the Gd-DTPA complex (gadopentetate dimeglumine) was used as template model. It was found that practically all elements present as contaminants in the formulation are able to replace Gd in the complex. Even endogenous metals such as Cu and Fe, which do not present any toxicological potential, may cause , due to transmetallation reations, free Gd3 + to be formed. / O gadolínio (Gd) é a base do meio de contraste mais utilizado em ressonância magnética (RM). Por se tratar de um íon metálico muito tóxico, todos os meios de contraste com Gd possuem agentes quelantes em sua composição. As formulações de Gd estão comercialmente disponíveis em concentrações de 0,5 e 1 mol L-1, sendo estas, quase exclusivamente, excretadas por via renal, sem produzir efeitos tóxicos. Porém, em 2006, dois grupos europeus independentes sugeriram uma relação entre a administração de complexos gadolínicos e a ocorrência de fibrose sistêmica nefrogênica (FSN) em pacientes com insuficiência renal. A FSN é uma doença grave, atribuída a reações de transmetalação do Gd de seus complexos por metais endógenos. Neste trabalho, utilizaram-se técnicas de espectrometria de absorção atômica, espectrometria de massa com plasma indutivamente acoplado e cromatografia líquida com detector de massa para investigar metais presentes como impurezas e/ou contaminantes em cinco formulações de contrastes a base de Gd e suas reações de transmetalação. Os resultados encontrados mostraram que outros metais, além do Gd, estão presentes nas formulações, os elementos terras-raras (Sc, Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er e Tm) e elementos como Al, As e Pb, sabidamente tóxicos para o ser humano. Para verificar a transmetalação, o complexo Gd-DTPA (Gadopentetato dimeglumina) foi utilizado como modelo e verificou-se que, praticamente, todos os elementos presentes como contaminantes nas formulações substituíram o Gd no complexo, ou seja, mesmo a presença de metais endógenos como Cu e Fe, que não apresentariam potencial toxicológico podem, através da transmetalação, levar à presença de Gd3+ livre.

Abstract The rare-earth elements (REEs) and bismuth, being classified as the ‘most critical raw materials’ (European Raw Materials Initiatives, 2017), have a high economic importance to the EU combined with a high relative supply risk. REEs are highly important for the evolving technologies such as clean-energy applications, high-technology components, rechargeable batteries, permanent magnets, electric and hybrid vehicles, and phosphors monitors. This scientific research work aims at building a fundamental knowledge base concerning the electronic/molecular structure and properties of rare-earth element (REE) and bismuth complexes with dithiocarbamate (DTC) and 1,10-phenanthroline (PHEN) by employing state-of-the-art experimental techniques such as nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction (XRD) techniques together with ab initio quantum mechanical computational methods. This combination of methods has played a vital role in analysing the direct and significant effect of the heavy metal ions on the structural and magnetic resonance properties of the complexes, thereby, providing a framework of structure elucidation. This is of special importance for REEs, which are known to exhibit similar chemical and physical properties. The objectives of the work involve i) a systematic investigation of series of REE(III) as well as bismuth(III) complexes to get a profound understanding of the structure-properties relationship and ii) to find an appropriate theoretical modelling and NMR calculation methods, especially, for heavy metal systems in molecular and/or solid-state. This information can later be used in surface interaction studies of REE/bismuth minerals with DTC as well as in design and development of novel ligands for extraction/separation of metal ions. The REE(III) and bismuth(III) complexes with DTC and PHEN ligands have all provided a unique NMR fingerprint of the metal centre both in liquid and solid phase. The solid-state ¹³C and ¹⁵N NMR spectra of the diamagnetic REE(III) and bismuth(III) complexes were in accord with their structural data obtained by single crystal XRD. The density functional theory (DFT) methods were used to get complementary and refined structural and NMR parameters information for all diamagnetic complexes in the solid-state. The relativistic contributions due to scalar and spin-orbit correlations for the calculated ¹H/¹³C/¹⁵N chemical shifts of REE complexes were analysed using two-component zeroth-order regular approximation (ZORA)/DFT while the ‘crystal-lattice’ effects on the NMR parameters were calculated by combining DFT calculations on molecular and periodic solid-state models. The paramagnetic REE complexes display huge differences in their ¹H and ¹³C NMR spectral patterns. The experimental paramagnetic NMR (pNMR) chemical shifts, as well as the sizable difference of the ¹H and ¹³C NMR shifts for these isoelectronic complexes, are well reproduced by the advanced calculations using ab initio/DFT approach. The accuracy of this approach is very promising for further applications to demanding pNMR problems involving paramagnetic f-block elements. The results presented in this thesis demonstrate that a multidisciplinary approach of combined experimental NMR and XRD techniques along with computational modelling and property calculations is highly efficient in studying molecular complexes and solids containing heavy metal systems, such as rare-earths and bismuth.