Dissertations / Theses on the topic 'Rare earth elements'

The HREE are generally considered to be the most critical of the REE, indispensable for many high-tech applications such as smart-phones and electric vehicles. Currently, carbonatites are the main source of REE due to their high REE grade; most carbonatites, however, are HREE-poor. This thesis presents the findings on HREE mineralisation at the Songwe Hill carbonatite, in the CAP of south-eastern Malawi. Across all carbonatite types at Songwe, whole-rock Y and P2O5 concentrations correlate positively, indicating that phosphate minerals have a strong control over the HREE contents. This is confirmed through textural and geochemical analyses (LA ICP-MS and EPMA) of apatite, which show that it can be subdivided into 5 different types (Ap-0–4), found at different stages of the paragenetic sequence. The chemistry of each of these apatite types becomes progressively more HREE-enriched, up to 3 wt. % Y2O3, and ultimately culminating in xenotime crystallisation. Cross-cutting relationships indicate that HREE-enriched apatite formed as an early crystallisation product from a late-stage, carbonatite-derived hydrothermal fluid. It is evident that LREE-fluorcarbonate mineralisation occurred after apatite crystallisation and it is assumed that crystallisation of all hydrothermal phases was though the evolution of a single fluid, rather than several different fluids. The apatite composition is compared to a compilation of analyses of apatite from other carbonatites and granitoids, as well as new analyses of late-stage apatite from the Kangankunde and Tundulu carbonatites, Malawi. Based on these analyses, it is concluded that apatite from Songwe has the highest HREE concentration compared to apatite from any previously analysed carbonatite. However, apatite from the Tundulu carbonatite has a similar geochemistry and paragenesis to the HREE-rich apatite from Songwe, suggesting that late-stage HREE enrichment may be a common process in carbonatites. In order to elucidate the fluid conditions which led to HREE mineralisation, new fluid inclusion and stable isotope data are presented to complement the mineralogical data. The fluid inclusions constrain the minimum temperature of apatite crystallisation of 160 °C, and most homogenisation temperatures in apatite are between 160-360 °C. Inclusions from apatite are CO2-rich, and it is suggested that transport of the REE occurred in carbonate complexes. Stable isotope data were obtained from both conventional C and O analyses of carbonates and from a novel method developed for acquiring δ18OPO4 from apatite. A conceptual model involving the simultaneous cooling and mixing of magmatically-derived and meteoric fluids is suggested. Two possible causes of REE fractionation are suggested: (1) a crystal-chemical control and (2) control through preferential stability of LREE and HREE complexes. However, neither mechanism is equivocal and further work on the stability of carbonate complexes is suggested in order to better understand REE mineralisation at carbonatites In addition to results on the HREE mineralisation in carbonatites, new data on the mineralogy, geochemistr y and age of the Songwe Hill carbonatite and the closely-associated Mauze nepheline syenite intr usion are presented. Songwe compr ises three stages of intr usion (C1–3): (C1) sovitic calcite carbonatite, (C2) alvikitic calcite-carbonatite and (C3) Fe-rich carbonatite. The LREE grade increases with the increasing Fe-content of the intrusion, as is common at many REE-rich carbonatites. Later-stages of the intrusion include apatite-fluorite veins (C4) and Mn-Fe-veins. The former is a volumetrically minor stage, but can contain up to 1 wt. % Y2O3, and the latter is formed through oxidation of carbonatite by supergene fluids. Samples analysed from Mauze show that it is REE- and P2O5-poor, with MREE-depleted REE distributions. U-Pb dating of zircons from Songwe and Mauze show that they are 131.5 ± 1.3 and 133.1 ± 2.0 Ma, respectively. The close temporal association of each intrusion suggests that Mauze could be a ‘heat-engine’ for hydrothermal mineralisation at Songwe.

This thesis is directed towards the study of the solvent extraction behaviour of the lanthanides and aluminium, bismuth, calcium and zinc whose radii and/or charges are similar to those of the REE. A brief review of the fundamentals and classification of extraction systems and of extractants is presented in Chapter 1. Chapters 2 and 3 are reviews of the properties and uses of the lanthanides and solvent extraction using phosphonate and sulphonate extractants, respectively. Chapter 4 deals with experimental procedures, results, discussions and conclusions. The extraction of zinc (II), calcium (II), aluminium (III), bismuth (III) and some lanthanide ions from aqueous perchlorate solutions into hexane solutions of 2-ethylhexyl phenylphosphonic acid, HEH$\Phi$P, was studied. The mechanisms of extraction are discussed on the basis of the results obtained by slope analysis. Depending upon the size and charge of the ion, the extracted species contain varying numbers of extractant molecules and phosphonate groups as ligands. Monomeric complexes are formed in the presence of excess extractant. High loadings of the extractant phase with the metal ion resulted in suppression of the extraction. Alkali ions were not extracted but alkali perchlorate suppressed the extraction through the effect of ionic strength on the metal ion activity. To further investigate the mechanism of extraction, $\sp{31}$P NMR of the organic phase following extraction of lanthanum was studied. A polymeric lanthanum-HEH$\Phi$P complex which precipitates out in the organic phase is formed at high (saturation) loading of this phase. A structure is proposed for this complex. The thermodynamics of extraction of these ions from perchlorate solutions into petroleum ether solutions of dinonylnaphthalene sulphonic acid, DNNSA, and HEH$\Phi$P were studied. In the case of DNNSA, extraction of the trivalent ions is dominated by the enthalpy of complexing. Electrostriction of large complex micelles by the complexed ion is postulated in order to account for the entropy effect. For the divalent ions, the enthalpy of dehydration of the ion is more important. A strategy for improving the separation factors is proposed. In the case of HEH$\Phi$P, charge density of the cation has a major influence upon the mechanism of the reaction and in turn upon the thermodynamic parameters. The ionic strength of the aqueous phase influences the thermodynamic parameters in the HEH$\Phi$P and DNNSA systems. Amongst the REE, lanthanum shows a singular behaviour. The extractions have been compared with those that employ dinonylnaphthalene sulphonic acid and factors that are responsible for the greater selectivity of the phosphonate have been elucidated. Development of an extraction chromatographic separation procedure for the lanthanides with a view to separating them from other matrix elements and fractionating them among themselves was studied. This was to be achieved by employing an organic polar solvent in the later stages of column elution. However, low recoveries were observed upon ashing the organic eluent and DCP determinations. The presence of phosphate (as KH$\sb2$PO$\sb4$ or H$\sb3$PO$\sb4)$ was found to lead to depression of analyte signal (concentration) in the DCP.

Rare earth elements (REE) are known as the lanthanide series (La-Lu) plus yttrium (Y) and scandium (Sc). REE are essential materials for modern industries and especially for green technologies (wind turbines, batteries, lasers, catalysts, etc.). However, despite their high global demand, their supply is limited such that the EU has cataloged it as critical raw materials. In order to ensure the supply of REE in the future, the search for alternative sources of these elements worldwide has been promoted in recent years. Acid mine drainage (AMD) produced by the Fe-sulphide weathering can effectively leach Fe, Al, SO4, and REE from the host rock. This can lead to high concentrations of these liberated species in the affected waters. Thus, the REE concentrations in AMD can be between two and three orders of magnitude higher than natural waters, as such it can be considered as a complementary source of REE recovery. The increase of pH in AMD by mixing neutral waters results in the precipitation of iron oxy-hydroxysulfate (schwertmannite) from pH 3-3.5, and aluminum (basaluminite) from pH 4-4.5 in the river channels. This process may be accompanied by REE scavenging. Due to its acidity and high metal load, acid mine drainage presents a major environmental problem worldwide, therefore, different treatment systems have been developed to minimize its impact. Disperse Alkaline Substrate (DAS) passive remediation system neutralizes AMD by dissolving calcite, and allowing the sequential precipitation of schwertmannite and basaluminite in separated layers, where REE are preferably retained in the basaluminite-enriched waste. Despite this, there are still no studies describing the adsorption of REE on both basaluminite and schwertmannite in these environments. The REE scavenging mechanism is studied by adsorption on synthetic minerals of basaluminite and schwertmannite as a result of variation to the both the pH and sulfate concentration. A thermodynamic adsorption model is proposed based on experimental results in order to predict and explain the REE mobility in AMD mixtures with neutral waters and in a passive treatment system. Basaluminite and schwertmannite have a nanocrystalline character. Further, schwertmannite has been observed to transform into goethite on weekly timescales, resulting in sulfate release. However, there is a gap of knowledge about basaluminite stability at variable sulfate concentration and pH and its possible transformation to other more crystalline Al-minerals. In this study, basaluminite local order at different pH values and dissolved sulfate concentrations was characterized. Results demonstrate that basaluminite can transform to nanoboehmite in weeks under circumneutral pH. However, the presence of sulfate can inhibit this transformation. Separate adsorption experiments on both basaluminite and schwertmannite were performed with two different concentrations of SO4 while varying the pH (3-7). Results show that the adsorption is strongly dependent on pH, and to a lesser extent on sulfate concentration. Lanthanide and yttrium adsorption is most effective near pH 5 and higher, while that of scandium begins around pH 4. Due to the high concentrations of sulfate in acidic waters, the predominant aqueous REE species are sulfate complexes (MSO4+). Notably, Sc(OH)2+ represents a significant proportion of aqueous Sc. , A surface complexation model is proposed in which predominant aqueous species (Mz+) adsorb on the mineral surface, XOH, following the reaction: The adsorption of the lanthanides and yttrium occurs through the exchange of one and two protons from the basaluminite and schwertmannite surface, respectively, with the aqueous sulfate complexes. The sorbed species form monodentate surface complexes with the aluminum mineral and bidentate with the iron mineral. In the case of Sc, the aqueous species ScSO4+ and Sc(OH)2+ form bidentate surface complexes with both minerals. EXAFS analysis of the YSO4+ complex adsorbed on the basaluminite surface suggests the formation of a monodentate inner sphere complex, in agreement with the proposed thermodynamic model. Once the surface complexation model was validated, it was used to asses and predict the REE mobility in passive remediation systems and acidic water mixing zones with alkaline inputs from the field. The REE are preferentially retained in basaluminite-rich waste during passive remediation due to its sorption capacity between pH 5-6. In contrast, schwertmannite waste contains very little REE because the formation of this mineral occurs at pH lower than 4, which prevents REE adsorption. Further, Sc may be scavenged during schwertmannite precipitation as a result of this low pH The model correctly predicts the absence of REE in schwertmannite precipitates and the enrichment of the heavy and intermediate REE with respect to the light REE in basaluminite precipitates collected in the water mixing zones. However, there is a systematic overestimation of the fractionation of rare earths in basaluminite precipitate. This inaccuracy is mainly due to the fact that the mineral precipitation and adsorption are not synchronous process, while basaluminite precipitates from pH 4, REE adsorption occurs at higher pH values, between 5 and 7, when the water mixture reaches these values and a fraction of the particles have been dispersed.
Las tierras raras (en inglés rare earth elements, REE) son conocidas como el conjunto de la serie de los lantánidos (La-Lu), itrio (Y) y escandio(Sc). Las tierras raras son materiales indispensables para las industrias modernas y en especial para las tecnologías verdes (aerogeneradores, baterías, láseres, catalizadores, etc.). Sin embargo a pesar de su gran demanda mundial, su abastecimiento es limitado, por lo que han sido catalogadas por la UE como materias primas críticas (Critical Raw Materials). Con el objetivo de asegurar el abastecimiento de REE en el futuro, en los últimos años se ha promovido la búsqueda de fuentes alternativas de estos elementos en todo el mundo. El drenaje ácido de mina (en inglés acid mine drainage, AMD) producido por la meteorización de sulfuros de Fe, tiene un alto poder de lixiviación de las rocas, por lo que las aguas afectadas adquieren elevadas concentraciones en disolución de Fe, Al, SO4 y otros metales, como las REE. Así, las concentraciones de REE en AMD son entre dos y tres órdenes de magnitud superiores al resto de las aguas naturales y pueden suponer una fuente complementaria de recuperación de REE. El aumento de pH del AMD por mezcla con aguas neutras da lugar a la precipitación en los cauces de los ríos de oxy-hidroxisulfatos de hierro (schwertmannita), a partir de pH 3-3.5, y de aluminio (basaluminita), a partir de pH 4-4.5; acompañado de la eliminación de las tierras raras. Debido a su acidez y carga metálica, el drenaje ácido de mina presenta un problema medioambiental de primera magnitud, por lo que se han desarrollado diferentes sistemas de tratamiento para minimizar su impacto. El sistema de tratamiento pasivo Disperse Alkaline Substrate (DAS) produce la neutralización de las aguas ácidas por la disolución de la calcita presente en el sistema, permitiendo la precipitación secuencial, de schwertmannita y basaluminita. Las tierras raras quedan retenidas preferentemente en el residuo enriquecido en basaluminita. A pesar de ello, aún no existen estudios que describan la adsorción de tierras raras tanto en basaluminita como schwertmannita en estos ambientes. En esta tesis se estudia el mecanismo de retención de las tierras raras mediante adsorción en minerales sintéticos de basaluminita y schwertmannita, en función del pH y del contenido de sulfato disuelto. Con los resultados experimentales obtenidos, se propone un modelo termodinámico de adsorción para predecir y explicar la movilidad de las tierras raras observada en mezclas de AMD con aguas neutras y en un sistema de tratamiento pasivo. La basaluminita y la schwertmannita presentan un carácter nanocristalino. Es conocido que la schwertmannita se transforma en goethita en semanas, liberando sulfato. Sin embargo, nada se sabe de la basaluminita y su posible transformación a otros minerales de Al más cristalinos. De este modo, la caracterización del orden local de la basaluminita a diferentes valores de pH y sulfato se expone en primer lugar. Dependiendo del pH y el sulfato en disolución, la basaluminita se transforma en diferentes grados a nanoboehmita en semanas, pero tiende a estabilizarse con la presencia de sulfato en solución. Los experimentos de adsorción en basaluminita y schwertmannita con diferentes concentraciones de SO4 realizados para cada mineral y en rangos de 3-7 de pH han demostrado que la adsorción es fuertemente dependiente del pH, y en menor medida del sulfato. La adsorción de los lantánidos y del itrio es efectiva a pH 5, mientras que la del escandio comienza a pH 4. Debido a las altas concentraciones de sulfato en aguas ácidas, las especies acuosas predominantes de las tierras raras son los complejos con sulfato, MSO4+. Además del complejo sulfato, el Sc presenta importantes proporciones de Sc(OH)2+ en solución. En función de la dependencia del pH y de la importancia de la especiación acuosa, se propone un modelo de complejación superficial donde la especie acuosa predominante (Mz+) se adsorbe a la superficie libre el mineral, XOH, cumpliendo la siguiente reacción: La adsorción de los lantánidos y del itrio se produce a través del intercambio de uno o dos protones de la superficie de la basaluminita o de la schwertmannita, respectivamente, con los complejos sulfato acuoso, formando complejos superficiales monodentados con el mineral de aluminio y bidentados con el de hierro. En el caso del Sc, las especies acuosas ScSO4+ y Sc(OH)2+ forman complejos superficiales bidentados con ambos minerales. Complementando el modelo propuesto, el análisis de EXAFS del complejo YSO4+ adsorbido en la superficie basaluminita sugiere la formación de un complejo monodentado de esfera interna, coincidiendo con el modelo termodinámico propuesto. El modelo de complejación superficial, una vez validado, ha permitido evaluar y predecir la movilidad de REE en los sistemas de tratamiento pasivos y en zonas de mezcla de aguas ácidas con aportes alcalinos estudiados en el campo. La preferente retención de las tierras raras en la zona de la basaluminita precipitada en los sistemas de tratamiento pasivo ocurre por adsorción de las mismas a pH entre 5-6. La ausencia de tierras raras en la zona de schwertmannita se debe al bajo pH de su formación, inferior a 4, que impide la adsorción de las mismas. Sin embargo, debido a su menor pH de adsorción, una fracción de Sc puede quedar retenida en la schwertmannita. El modelo también predice correctamente la ausencia de REE en los precipitados de schwertmannita y el enriquecimiento de las tierras raras pesadas e intermedias respecto a las ligeras en los precipitados de basaluminita recogidos en el campo en las zonas de mezcla de aguas. Sin embargo, se ha observado una sistemática sobreestimación del fraccionamiento de las tierras raras en los precipitados de basaluminita. Este hecho se debe principalmente a que la precipitación del mineral no ocurre de forma síncrona con la adsorción, precipitando la basaluminita a partir de pH 4 y adsorbiendo tierras raras a pH más altos, entre 5 y 7, cuando las partículas sólidas han sido parcialmente dispersadas.

The rare earth elements are a group of 17 elements consisting of the lantahnide series, scandium and yttrium. The application with the largest rare earth consumption is the permanent rare earth magnets. The neodymium-iron-boron magnets are the strongest permanent magnetic material known and are widely used. There is a concern that there will be a shortage in Nd-Fe-B magnets in short time. This has lead to an increased interest in the recycling of the rare earth magnets in the world.This project gives a very brief introduction to the Nd-Fe-B magnets, their uses and recycling. Two types of experiments that aims at recovery of neodymium from Nd-Fe-B magnets have been performed; extraction of neodymium by the use of molten silver and extraction of neodymium by direct oxidation. In the liquid silver experiments, extraction was obtained, but the analysis gave equivocal results. In the direct oxidation experiment, the separation of an iron phase and a neodymium oxide phase failed, and the experiment was not seen as successful.Magnetic waste from WEEE Recycling was also performed, and it turned out to contain small amounts of rare earth elements.

The rare earth elements (REE) constitute much of Group 3 of the periodic table, a group of 16 transition metals, including the lanthanide series (La to Lu, excluding Pm), yttrium (Y) and scandium (Sc).

This thesis is concerned with the liquid-liquid extraction and separation of Y, Ce, La, binary mixtures, and ternary mixtures as well as synthesis of novel amide ligands for the extraction of rare earth elements. Chapter I is the general introduction of the practical process and applications of solvent extraction and its theory. It describes systems involving compound formation, ion-association and solvation as well as solvent loading capacity, dispersion and coalescence. The aims of this thesis are also presented. Chapter 2 presents an introduction to yttrium chemistry and recent developments in yttrium extraction chemistry. It describes the relevant factors affecting the liquidliquid extraction process to determine the optimum conditions for yttriurn extraction from sulfate liquor. These factors include TiOA concentration, contact time, pH value, temperature, aqueous phase composition, diluent and construct of McCabe-Thiele diagram. In addition, the synergistic effect of using TBP, TOPO and D2EHPA and the optimum conditions for the stripping process are deten-nined. Chapter 3 contains introduction to cerium chemistry and recent developments in cerium extraction chemistry. The optimum conditions for solvent extraction of cenum(III) from a sulfate medium, and synergistic effects using TOPO and D2EHPA on the extraction process are studied. Also, the relevant factors affecting cerium(Ill) stripping efficiency are determined. Chapter 4 presents a brief introduction to lanthanum and recent developments in lanthanum extraction chemistry. The optimum conditions for solvent extraction of lanthanum from sulfate media, with synergistic effects using TOPO, D2EHPA and TBP are described. In addition, the suitable conditions for the lanthanum stripping process are determined. Chapter 5 contains the principles of separation and liquid-liquid extraction of binary (Y/La) and ternary (Nd-La-Y) element systems. The optimum conditions for the separation of both systems were investigated. Chapter 6 describes the synthesis and characterization of several novel piperazine and piperidine amide ligands. These ligands have good extraction ability for both light and heavy rare earth elements. The optimum conditions for solvent extraction of yttnum and cerium(III) using these ligands were studied. The chapter also, contains the experimental procedures and characterising data for ligand synthesis in this thesis.

Rare earth elements (REEs) are important for establishing a technology based society, however are difficult to process. The use of biomining for the extraction of REEs minerals offers a benign alternative to conventional hydrometallurgical routes with more selective solubilisation of REEs over radionuclides. The use of phosphate solubilising microorganisms in the bioleaching of REEs was investigated to gain a better understanding of the leaching behaviour of individual REEs and the mechanism attributed to their mobilisation.

Pour faire face au défi du changement climatique, de nouvelles technologies ont récemment émergé, permettant l’exploitation ou le stockage d’énergies renouvelables. Des éoliennes aux voitures électriques, des solutions prometteuses apparaissent pour adapter nos modes de vie. Ces technologies ajoutent cependant une pression sur d’autres ressources non renouvelables, parmi lesquelles les terres rares (TR). Ces 16 éléments, constitués des 14 lanthanides, de l’yttrium (Y) et du scandium (Sc), sont au cœur des technologies actuelles. Les technologies de la communication (écrans des smartphones, fibres optiques) et de l’armement (superalliages), aujourd’hui estimées essentielles, accroissent encore la demande pour ce groupe d’éléments, faisant partie de la liste des « matières premières critiques » proposée par l’Union Européenne.Leur extraction lors des dernières décennies a laissé derrière elle un paysage morcelé, notamment dans le Sud de la Chine. Aujourd’hui interdites, les pratiques de décapage puis excavation, suivies d’une lixiviation en tas, ont légué des centaines d’hectares de stériles miniers. Ces milieux dégradés, qui étaient autrefois des forêts tropicales, sont sujets à une érosion intense, et contiennent encore des TR à faible concentration. Dans un contexte où les services écosystémiques des milieux naturels sont plus que jamais indispensables, est apparue la volonté de refonctionnaliser ces sols délaissés. Des aides gouvernementales chinoises ont été déployées pour leur revégétalisation à grande échelle. Des programmes de recherche ont aussi été lancés pour mieux comprendre le fonctionnement de ces écosystèmes dégradés et envisager leur restauration. Dans ce cadre, une des clés de la réussite pourrait être le recours à des plantes adaptées localement, et présentant un intérêt économique, pour la production d’énergie, de fibres, ou la récupération des terres rares présentes dans les stériles. La filière « agromine » est une solution fondée sur la nature, qui combine la culture de plantes hyperaccumulatrices et de la récupération des métaux à partir de ces plantes. Cette filière pourrait être très intéressantes dans ce contexte, puisque les espèces D. linearis L. et P. americana, hyperaccumulateurs de TR sont présentes sur ces anciens sites miniers. Ces plantes concentrent les TR dans leurs partie aériennes, jusqu’à des valeurs supérieures aux minerais exploités.La récupération des TR, via des procédés hydrométallurgiques, permettrait alors de concrétiser la valeur économique de ces plantes, et contribuerait à l’approvisionnement en TR, nécessaire au déploiement des technologies modernes. L’objectif de cette thèse, qui fait suite à celle de Z . Chour (2018, Univ. Lorraine) est de développer et optimiser des procédés de récupération de TR à partir des cendres de D. linearis et de la plante P. americana, qui a des caractéristiques botaniques, et physico-chimiques différentes. Il s’agit aussi d’étudier l’impact environnemental et le coût des différents procédés identifiés. Elle a été menée en co-direction entre l’Université de Lorraine (Nancy, France) et l’Université Sun Yat-sen (Canton, Chine). Ce travail a permis de répondre à des questions scientifiques sur la séparation de TR à faible concentrations dans des matrices riches en silice et contenant aussi de l’aluminium. Il a abouti à la conception et l’optimisation d’un procédé original à partir de D. linearis, accompagné d’une comparaison de différents procédés, au plan des consommation de matière et d’énergie et de la production des déchets, et d’une évaluation économique. Il constitue ainsi une étape essentielle à la fois pour le développement scientifique de la filière agromine et pour sa mise en œuvre
To meet the challenge of climate change, new technologies have recently emerged that allow the use or storage of renewable energy. From wind turbines to electric cars, promising solutions are emerging to adapt our lifestyles. However, these technologies are adding pressure on other non-renewable resources, including rare earth elements (REEs). These 16 elements, made up of the 14 lanthanides, yttrium (Y) and scandium (Sc), are at the heart of current technologies. Communication technologies (smartphone screens, optical fibers) and weapons technologies (superalloys), which are now considered essential, are further increasing the demand for this group of elements, which are on the list of "critical raw materials" proposed by the European Union.Their extraction over the last decades has left behind a fragmented landscape, especially in Southern China. Now banned, the practices of stripping and excavation, followed by heap leaching, have resulted in hundreds of hectares of tailings. These degraded environments, which were once tropical forests, are subject to intense erosion and still contain low concentrations of REEs. In a context where the ecosystem services of natural environments are more essential than ever, the desire to refunctionalize these derelict soils has emerged. Chinese governmental aid has been deployed for their large-scale revegetation. Research programs have also been launched to better understand the functioning of these degraded ecosystems and to consider their restoration.In this context, one of the keys to success could be the use of locally adapted plants that are of economic interest for the production of energy, fibers, or the recovery of rare earths present in the tailings. The "agromining" chain of processes is a nature-based solution, which combines the cultivation of hyperaccumulator plants and the recovery of metals from these plants. This chain could be very interesting in this context, since the species D. linearis L. and P. americana, hyperaccumulators of REEs, are present on these former mining sites. These plants concentrate the REEs in their aerial parts, up to values higher than the exploited ores. The recovery of the REEs, via hydrometallurgical processes, would then make it possible to concretize the economic value of these plants, and would contribute to the supply of REEs, necessary for the deployment of modern technologies.The objective of this thesis, which follows that of Z . Chour (2018, Univ. Lorraine) is to develop and optimize REE recovery processes from the ash of D. linearis and from the plant P. americana, which has different botanical, and physicochemical characteristics. The environmental impact and cost of the different processes identified were also studied. This research was conducted in co-supervision between the University of Lorraine (Nancy, France) and Sun Yat-sen University (Canton, China).This work allowed to answer scientific questions on the separation of REEs at low concentrations in silica-rich matrices also containing aluminium. It led to the design and optimization of an original process using D. linearis, accompanied by a comparison of different processes, in terms of material and energy consumption and waste production, and an economic evaluation. It is thus an essential step both for the scientific development of the agromining process and for its implementation

Sällsynta jordartsmetaller är en kritisk råvara som står inför viktiga utmaningar gällande utbud och efterfrågan. För att överkomma dessa utmaningar behövs det effektiva separationsmetoder. Den här rapporten studerar separationen av sällsynta jordartsmetaller med extraktionskromatografi. Tre olika extrakt-modifierade HPLC kolonner användes för att separera en samling av åtta sällsynta jordartsmetaller; lantan, cerium, praseodym, neodym, samarium, gadolinium, dysprosium och yttrium. Den första kolonnen innehöll ren HDEHP som extraktant, den andra ren HEHEHP som extraktant. Den tredje kolonnen innehöll en blandning av de två extrakanterna. Blandningen bestod av 15–30% HDEHP. Eluering genomfördes med salpetersyra i olika koncentrationer och applicering. Forskningsfrågan som rapporten bygger på gäller hurvida blandningen av extraktanterna kan förbättra separationen gentemot att endast använda de rena extraktanterna. Jämförelsen kolonnerna emellan baserades huvudsakligen på två parameterar, salpetersyraförbrukning och upplösning av toppar.  Resultaten visar att kolonnen med endast HEHEHP hade minst salpetersyraförbrukning men gav sämst upplösning. Kolonnen med endast HDEDP hade högst salpetersyraförbrukning men gav bäst upplösning, speciellt för de fyra tyngsta ämnena; samarium, gadolinium, dysprosium och yttrium. Kolonnen med extraktantblandningen gav god upplösning för alla ämnen, speciellt för de fyra lättaste ämnena; lantan, cerium, praseodym och neodym. Eftersom denna kolonn dessutom hade relativt låg salpetersyraförbrukning är den preliminära slutsatsen att denna presterade bäst generellt. Slutsatsen är därmed att extraktantblandningen kan förbättra separationen.
Rare earth elements are a crucial resource facing challenges concerning supply and demand. To meet these challenges, efficient separation methods are needed. This report investigates the separation of rare earth elements using extraction chromatography. Three different extractant modified HPLC columns was used to separate a collection of eight rare earth elements: lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, and yttrium. One column contained pure HDEHP as extractant, another pure HEHEHP as extractant. The third column contained mixture of the two extractants. The mixture contained 15-30% HDEHP. Elution was achieved using nitric acid as eluent in different concentrations and modes of elution. The research question guiding the work was to investigate if using a mixture of extractants could improve the separation as opposed to using only the pure extractants. The comparison was made based on two main performance parameters, nitric acid consumption and peak resolution.  The results show that the column with pure HEHEHP had the lowest nitric acid consumption but yielded the worst resolution. The column with pure HDEHP had the highest nitric acid consumption but the best resolution, particularly for the four heaviest analytes, samarium, gadolinium, dysprosium, and yttrium. The column with the extractant mixture yielded good resolution for all analytes and especially for the four lightest analytes: lanthanum, cerium, praseodymium, and neodymium. Since this column also had relatively low nitric acid consumption the tentative conclusion is that it performed the best overall. The conclusion is therefor that the extractant mixture can improve the separation.

The demand for rare earth elements (REEs) has increased over the last decade due to applications in high technology devices including those in the defense industry. The recovery of REEs from primary sources such as rare earth minerals are viable using physical separations followed by chemical processing. However, weak market values and environmental concerns have limited the viability of such operations. On the other hand, REE recovery from secondary sources such as apatite ore, bauxite waste, and waste recycling, provides an opportunity to take advantage of a resource that does not require mining costs as well as other associated costs given that these expenses are covered by the revenue generated from the production of the primary material. Coal-based materials represent a potential source for REEs which may be extracted and concentrated by the use of physical and/or chemical processes. The current study focused on developing a leaching process to extract REEs from the pre-combustion coal sources including coarse and fine refuse and low-valued material obtained from coal preparation plants. Materials collected for leaching characteristic studies were found to have average total REE concentrations in the range of 200-350 ppm on a whole sample basis. Mineralogy studies performed on Fire Clay seam coal refuse using SEM-EDS detected micro-dispersed rare earth phosphate mineral particles which are generally difficult to dissolve in strong acid solutions. On the other hand, XRD analysis results from a high REE content segment of the West Kentucky No. 13 coal seam indicated the presence of fluorapatite which is soluble in weak acid solutions. The mineral associations of REEs were studied by extracting REEs using different types of acids under various pH conditions. Differential extraction of the REEs was examined along with the associated impurity elements such as iron, aluminum, and calcium among others. The findings showed that the light REEs were primarily associated in a phosphate mineral form, whereas the heavy REEs were mostly present in an ion substitution form associated with clay minerals. Relatively high concentrations of REEs were discovered in mixed-phase particles consisting of both coal and mineral matter. By reducing the particle size, more leachable forms of REEs were liberated and recovered along with the associated mineral matter embedded in the coal structure. The type of lixiviant played an important role during the initial stage of leaching but was found to be insignificant as the system reached equilibrium. Solids concentration in the leaching medium has an important role in establishing the throughput capacity of the leaching system. Test results found that an increase in solids concentration had a significant negative effect on rare earth recovery. This finding may be explained by higher concentrations of soluble calcium-based minerals such as calcite which provided localized pH increases near and within the pores of the solids. The result was precipitation of CaSO4 within the pores which blocked access for the lixiviants. This hypothesis was supported by the findings from BET and XPS analyses which found lower pore volume in high solid concentration systems and the existence of CaSO4 on the surface of the solids. Leaching test results obtained using sulfuric acid over a range of temperatures showed that the leaching process was mainly driven by a diffusion control process. The activation energy determined for an Illinois No. 6 coal source was 14.6 kJ/mol at the beginning of the reaction and 35.9 kJ/mol for the rest of the leaching process up to 2 hours. For material collected from the Fire Clay coal seam, the apparent activation energy was 36 kJ/mol at the start of the leaching reaction and decreased to 27 kJ/mol over the remaining period of the test. The activation energy values were nearly equivalent to the upper-level values that generally define a diffusion control process and the lower values of a chemical reaction control process. The lack of clarity in defining a clear control mechanism is likely associated with the variability in associated mineralogy, various modes of occurrence of the REEs and the interfacial transfer of product through the porous structure of the coal-based particles which requires relatively high activation energy. As such, both diffusion control and chemical reaction control mechanisms are likely occurring simultaneously during the leaching process with diffusion control being more dominant.

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 º
C for 14 hrs. The expected reaction is given below. Li2CO3 + 6H3BO3 -->
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 º
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.

Erbium, a rare earth element, has been shown to exhibit characteristic luminescence at 1.54mum due to its internal 4f transition from the first excited state (4pi3/2) to the ground state (4pi5/2). As this emission wavelength falls inside the maximum transmission window of silicon based optical fibers, erbium doped silicon might lead to the opportunity of silicon based optoelectronics. The introduction of erbium in silicon allows excitation through electron-hole recombination and subsequent radiative emission from the rare earth centers. The works reported here describe the structural, electrical and optical properties of crystalline silicon codoped with erbium and boron by ion implantation technique. Four sets of samples, co-implanted with erbium and boron at different Er dose, implantation energy and at different conditions, were prepared. Post-implantation annealing has been performed to recover the implantation damage to an acceptable value and to activate the dopant atoms optically and electrically. PL and EL measurements have been performed in the temperature range between 80K to room temperature. The sample with the lowest erbium concentration and energy gives the best PL and EL results. The observed emission peaks in both PL and EL measurements were at around 1.129mum, ~1.303mum, 1.50mum and 1.597mum at 80K. At higher temperatures, a broader peak at around 1.50mum with long tail towards the both end of wavelength has been observed. The peak at 1.129mum corresponding to the Si band edge emission, the reason for the peaks at around l.303mum has not been identified while the remaining two peaks correspond the Er3+ emission. Virtually no temperature quenching of Er luminescence is observed in some samples rather room temperature intensity is higher than that at 80K. The improvement of the temperature quenching effect on Er luminescence at room temperature has been attained in our results, which is significant improvement in comparison to the result found in the literature. The structural properties were studied by TEM in both cross-sectional and plan view configurations. TEM analyses showed dislocation loops and other defects of random size and distribution from the surface to 600nm below the surface. Er precipitates defects were also seen in the sample doped with Er comparatively at higher dose (1x1015Er/cm2) and energy (1.0 MeV). No detectable room temperature PL and EL signals were observed from the sample implanted at higher doses and energies.

Philosophiae Doctor - PhD
Coal fly ash has been studied extensively to understand the environmental impacts associated with its disposal, management and reuse. Although several beneficiation processes have been proposed, there has been little or no emphasis on the environmental safety of such processes, products and wastes. Elemental analysis has revealed that toxic elements and radionuclides are present in coal fly ash. Rare earth elements (REE) such as La, Ce and Y are also present in significant amounts in coal fly ash. The aims of this study were to determine the total elemental composition of coal fly ash using different analytical techniques; to validate the application potentials of fly ash beneficiation processes in terms of their environmental safety; and to valorise coal fly ash with a view of recovering REE either by concentrating or leaching the REE in the coal fly ash, products or waste from the beneficiation processes. The beneficiation processes studied were treatment of acid mine drainage (AMD) with fly ash; and the synthesis of geopolymer from fly ash. The fresh fly ash sample used in this study was collected directly from the hoppers at Matla power station and the AMD sample was collected from Carletonville goldmine. A total of 54 major, trace and REE were accurately determined in the ash using different analytical techniques. It was shown that the elemental content of Matla fly ash was of the same order as the SRM NIST coal fly ash 1633b. The comparative study of the four analytical techniques established that ENAA can accurately determine the major, minor and trace elements; that XRF is best suited for the determination of the major and minor elements, whilst the LA ICP-MS is reliable for trace elements determination. The solid residue (AMD/FA) resulting from the AMD interaction with fly ash was characterized with fly ash and the results compared. The results revealed that the amounts of La (141.09 ± 3.85 mg/kg), Ce (27.45 ± 2.04 mg/kg), and Nd (63.73 ± 0.05 mg/kg) in AMD/FA residue was considerably higher than their average abundance in the earth crust that varies from 66 mg/kg in Ce and 40 mg/kg in Nd to 35 mg/kg in La. The results also showed that the AMD/FA residue contained As (11.39 ± 1.21 mg/kg), Cd (3.77 ± 0.02 mg/kg), Cr (72.43 ± 1.27 mg/kg), Hg (10.50 ± 0.85 mg/kg), Ni (124.15 ± 1.6 mg/kg) and Pb (22.46 ± 1.43 mg/kg) which are potentially harmful if leached in to the environment in excessive amounts.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho, métodos analíticos foram desenvolvidos para a determinação de elementos terras raras (REE, do inglês Rare Earth Elements), por espectrometria de massa e espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-MS e ICP OES) numa amostra de asfalto. Foram avaliados os resultados analíticos através da análise de um material de referência certificado de rocha (GSP-1) e através da comparação dos resultados obtidos pelas duas técnicas. Dois diferentes métodos de lixiviação ácida foram empregados para o tratamento da amostra de asfalto, com HNO3 ou H2SO4, de maneira a simular os efeitos intensificados da chuva ácida. Também foi avaliada a extração da amostra com solvente orgânico e posterior lixiviação ácida, para identificar a origem (orgânica ou inorgânica) dos REE na amostra do asfalto, concluindo que eles estão presentes apenas na fração inorgânica da amostra. Os limites de detecção variaram entre 0,002 e 0,010 microgramas L elevado a menos 1 para a lixiviação com HNO3 e entre 0,001 e 0,014 microgramas L elevado a menos 1 com H2SO4, por ICP-MS, e entre 0,05 e 2,5 micrograma L elevado a menos 1 com HNO3 e entre 0,06 e 3,1 micrograma L elevado a menos 1 com H2SO4, por ICP OES. As determinações foram feitas com curvas analíticas com padrões aquosos e Rh como padrão interno. Além disso, a interferência espectral do BaO sobre Eu foi reduzida, através da precipitacao do Ba como BaSO4 quando se usou ácido sulfúrico para a lixiviacao da amostra de asfalto, reduzindo cerca de 94 porcento a concentracao de Ba em relação àquela medida no lixiviado com HNO3. As concentrações de REE variaram de 0,47 a 65,6 microgramas g menos 1, sendo que os terras raras leves (LREE) representaram 83 porcento do total de REE no asfalto investigado. O Ce foi o mais abundante dos REE no lixiviado do asfalto, seguido por Nd e La. A ordem das concentrações médias de REE no asfalto foi, em ordem decrescente: Ce maior Nd maior La maior Pr maior Sm maior Eu maior Gd maior Dy maior Er maior Yb maior Ho maior Tm maior Lu.
In this study, analytical methods were developed for the determination of Rare Earth Elements by inductively coupled plasma -mass and -optical emission spectrometries (ICP-MS and ICP OES), in an asphalt sample. The analytical results were evaluated through the analysis of a rock certified reference material (GSP-1) and through the comparison of the results with the two techniques. Two different methods of acid leaching were employed for the asphalt sample treatment, with HNO3 or H2SO4, in order to simulate intensified acid rain effects. Additionally, the extraction of the sample with organic solvent and subsequent acid leaching was also evaluated to identify the origin (organic or inorganic) of REE in asphalt sample, concluding that they are present in the sample inorganic fraction. The obtained limits of detection ranged from 0.002 to 0.010 microgam L to the power of minus 1 for the leaching with HNO3 and from 0.001 to 0.014 microgram L to the power of 1 with H2SO4, by ICP-MS, and from 0.05 to 2.5 microgram L to the power of minus 1 with HNO3 and from 0.06 to 3.1 microgram L to the power of minus 1 with H2SO4, by ICP OES. The determinations were made with analytical curves with aqueous standards and Rh as internal standard. Moreover, the spectral interference by BaO on Eu was reduced, through the precipitation of Ba as BaSO4 when sulfuric acid was used for the asphalt sample leaching, decreasing about 94 percent the Ba concentration in relation to that measured in the leachate with HNO3. The concentrations of REE in the asphalt sample ranged from 0.47 to 65.6 microgran g to the power of minus 1, being the light rare earth elements (LREE) accounted for 83 percent of total REE on the asphalt investigated. Cerium was the most abundant REE in the asphalt leached, followed by Nd and La. The order of average concentrations of REE in the asphalt was, in descending order: Ce > Nd > La > Pr > Sm > Eu > Gd > Dy > Er > Yb > Ho > Tm > Lu.

Thesis (MScEng)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: At Skorpion Zinc mine, in south-west Namibia, zinc oxide ore is refined through sulphuric acid leaching, solvent extraction, electrowinning and casting of the final 99.995 % Zn metal. Over the last four years, the rare earth element concentrations, with particular reference to Y, Yb, Er and Sc, have significantly increased in the circulating electrolyte and the zinc-stripped organic phase streams in the electrowinning and solvent extraction processes. This project had two main objectives: firstly, the effect(s) of rare earths on the zinc solvent extraction and electrowinning processes were to be determined; based on these results, the second objective was to find a suitable method for removing rare earth elements from the organic phase during zinc solvent extraction. The investigation into the effect of the rare earths on zinc electrowinning showed that an increase of 100 mg/l in the electrolyte Y concentration caused a decrease of 6 % in current efficiency. The elemental order of decreasing current efficiency was found to be: Y > Yb > Er > Sc. In the zinc solvent extraction process, it was found that an increase in the total organic rare earth elements and iron concentration from 3100 to 6250 mg/l resulted in doubled viscosity and an increase in phase disengagement time from 100 to 700 seconds. The organic zinc loading capacity after two extraction stages was reduced by 1 – 3 g/l depending on the pregnant leach solution used. The detrimental effect of rare earth elements on solvent extraction and electroplating of zinc therefore justified the development of a rare earth element removal process. Stripping of low concentrations of rare earth elements from 40% D2EHPA diluted in kerosene to produce a clean organic for zinc extraction was investigated using bench-scale experiments in a glass jacketed mixing cylinder. For the rare earths, the best stripping agent was found to be H2SO4, followed by HCl and then HNO3. Hydrochloric acid achieved better Fe stripping than sulphuric acid. Acid concentration was tested in the range of 1 to 7 M, organic-to-aqueous ratio for the range of 0.25 to 6.0 and temperatures between 30 and 55 °C. More than 80% stripping of yttrium and erbium could be achieved at an optimum hydrochloric acid concentration of 5 M and more than 90% rare earth element (specifically Y, Er, Yb) stripping from the organic phase could be achieved with 5 M sulphuric acid. Stripping was improved by reducing the organic-to-aqueous ratio to as low as 0.5 and increasing the temperature. Stripping increased with increasing temperature in an S-shaped curve, flattening off at 50°C. The effect of O:A ratio was more significant than the effect of temperature on rare earth stripping. The results showed good repeatability, and were not limited by the rare earth concentration, agitation rate or equilibrium time in the range of set points used in the experiments. Statistical models were compiled to fit the experimental data obtained for Y, Yb, Er and Fe when stripped with sulphuric and hydrochloric acid respectively. All models showed dependence on the acid concentration and squared-concentration and interaction effects between the O:A ratio and temperature and stripping agent concentration were significant. The models were compiled for the experimental data obtained from stripping synthetically prepared organic and then tested on results obtained when stripping the plant organic phase. The following three process solutions were discussed for implementation on a plant scale for the removal of rare earths from the organic phase during zinc solvent extraction: Sulphuric acid stripping mixer settler or stripping column, improvement of available HCl stripping section and replacement of the organic inventory. The possibility of an oxalic acid precipitation process to obtain value from the rare earths as by-product was also discussed. It was concluded that the current process that uses HCl to strip off iron and rare earths would be the best practically and financially feasible process. Value can be gained from the rare earths if a rare earth element - oxalic acid precipitation section that is financially feasible can be established.
AFRIKAANSE OPSOMMING: By Skorpion Zinc myn, in suidwes Namibië, word sinkoksied erts gesuiwer deur middel van swaelsuur-loging, oplosmiddel ekstraksie, elektroplatering en gieting van die finale 99.995 % Zn metaal. Oor die afgelope vier jaar het die seldsame aardmetale konsentrasie, spesifiek Y, Yb, Er en Sc, noemenswaardig in die sirkulerende elektroliet en sink-gestroopte organiese fase toegeneem. Hierdie projek het twee hoofdoelstellings gehad: eerstens moes die effek van seldsame aardmetale op die sink oplosmiddel ekstraksie en elektroplatering prosesse bepaal word; gebaseer op hierdie resultate, was die tweede doelstelling om ‘n geskikte metode vir die verwydering van seldsame aardmetale vanaf die organiese fase gedurende sink oplosmiddel ekstraksie te vind. Die ondersoek na die effek van seldsame aardmetale op sink elektroplatering het gewys dat ‘n verhoging van 100 mg/l in die elektroliet Y konsentrasie ‘n verlaging van 6 % in kragdoeltreffendheid veroorsaak het. Die element-orde van verminderende kragdoeltreffendheid was Y > Yb > Er > Sc. Vir die sink oplosmiddel ekstraksie proses, is gevind dat ‘n verhoging in die totale organiese seldsame aardmetaal- en yster konsentrasie van 3100 tot 6250 mg/l ‘n verdubbelde viskositeit en ‘n verlenging in faseskeidingstyd van 100 tot 700 sekondes tot gevolg gehad het. Die organiese sink ladingskapasiteit na twee ekstraksie stappe is met 1 – 3 g/l verminder afhangende van die logings oplossing wat gebruik is. Die nadelige effek van seldsame aardmetale op oplosmiddel ekstraksie en sink elektroplatering het die ontwikkeling van ‘n seldsame aardmetale verwyderingsproses regverdig. Die verwydering van lae konsentrasies seldsame aardmetale vanaf die D2EHPA-keroseen organiese fase om ‘n skoon organiese fase vir sink-ekstraksie te verkry is ondersoek deur banktoetsskaal eksperimente. Vir die seldsame aardmetale is bevind dat H2SO4 die beste stropingsagent is, gevolg deur HCl en dan HNO3. Soutsuur het beter yster verwydering as swaelsuur bewerkstellig. Suurkonsentrasies van 1 tot 7 M, O:A verhoudings van 0.25 tot 6 en temperature tussen 30 en 55°C is getoets. Meer as 80% verwydering van yttrium en erbium kon bereik word met ‘n optimum HCl konsentrasie van 5 M en meer as 90% seldsame aardmetale (spesifiek Y, Er en Yb) verwydering vanaf die organiese fase met 5 M swaelsuur. Seldsame aardmetale en yster verwydering kon verbeter word deur die organies-tot-waterfase (O:A) verhouding te verminder tot so laag as 0.5 en deur die temperatuur te verhoog. Stroping het in ‘n S-kurwe verhoog soos die temperatuur verhoog het, en het afgeplat teen 50°C. Die effek van die O:A verhouding was belangriker as die effek van temperatuur op stroping. Die resultate het goeie herhaalbaarheid gewys, en is nie deur massaoordrag beperk nie. Statistiese modelle is saamgestel om die eksperimentele data wat vir Y, Yb, Er en Fe verkry is vir stroping met swaelsuur en soutsuur te pas. Al die modelle het afhanklikheid van die suurkonsentrasie en kwadratiese suurkonsentrasie gewys en interaksie effekte tussen die O:A verhouding, temperatuur en suurkonsentrasie was belangrik. Die modelle is saamgestel vir die eksperimentele data wat verkry is vanaf stroping van ‘n sintetiese organiese fase en is toe getoets op resultate wat verkry is vanaf stroping van die aanleg se organiese fase. Die volgende drie proses-oplossings is oorweeg vir implementering op ‘n aanlegskaal vir die verwydering van seldsame aardmetale vanaf die organiese fase gedurende sink oplosmiddel ekstraksie: Swaelsuur stroping menger-afskeidingstenk of stropingskolom, verbetering van die bestaande HCl aanleg en vervanging van die organiese inventaris. ‘n Moontlike oksaalsuur presipitasie proses om waarde vanaf die seldsame aardmetale as by-produk te verkry is ook bespreek. Daar is tot die gevolgtrekking gekom dat die huidige proses wat HCl gebruik om yster en seldsame aardmetale van die organiese fase af te stroop, die beste praktiese en finansieel vatbare proses huidiglik is. Waarde kan vanaf die seldsame aardmetale verkry word as ‘n seldsame aardmetale – oksaalsuur presipitasie afdeling wat finansieel haalbaar is daargestel kan word.

Master of Science
Department of Geology
Matthew Totten
The REE distribution patterns and total concentrations of the organic matter of the Woodford shale reveal a potential avenue to investigate hydrocarbon maturation processes in a source rock. Ten samples of the organic matter fraction and 10 samples of the silicate-carbonate fraction of the Woodford shale from north central Oklahoma were analyzed by methods developed at KSU. Thirteen oil samples from Woodford Devonian oil and Mississippian oil samples were analyzed for REE also. REE concentration levels in an average shale range from 170 ppm to 185 ppm, and concentration levels in modern day plants occur in the ppb levels. The REE concentrations in the organic matter of the Woodford Shale samples analyzed ranged from 300 to 800 ppm. The high concentrations of the REEs in the Woodford Shale, as compared to the modern-day plants, are reflections of the transformations of buried Woodford Shale organic materials in post-depositional environmental conditions with potential contributions of exchanges of REE coming from associated sediments. The distribution patterns of REEs in the organic materials normalized to PAAS (post-Archean Australian Shale) had the following significant features: (1) all but two out of the ten samples had a La-Lu trend with HREE enrichment in general, (2) all but two samples showed Ho and Tm positive enrichments, (3) only one sample had positive Eu anomalies, (4) three samples had Ce negative anomalies, although one was with a positive Ce anomaly, (5) all but three out of ten had MREE enrichment by varied degrees. It is hypothesized that Ho and Tm positive anomalies in the organic materials of the Woodford Shale are reflections of enzymic influence related to the plant physiology. Similar arguments may be made for the Eu and the Ce anomalies in the Woodford Shale organic materials. The varied MREE enrichments are likely to have been related to some phosphate mineralization events, as the Woodford Shale is well known for having abundant presence of phosphate nodules. The trend of HREE enrichment in general for the Woodford Shale organic materials can be related to inheritance from sources with REE-complexes stabilized by interaction between the metals and carbonate ligands or carboxylate ligands or both. Therefore, a reasonable suggestion about the history of the REEs in the organic materials would be that both source and burial transformation effects of the deposited organic materials in association with the inorganic constituents had an influence on the general trend and the specific trends in the distribution patterns of the REEs. This study provides a valuable insight into the understandings of the REE landscapes in the organic fraction of the Woodford Shale in northern Oklahoma, linking these understandings to the REE analysis of an oil generated from the same source bed and comparing it to oil produced from younger Mississippian oil. The information gathered from this study may ultimately prove useful to trace the chemical history of oils generated from the Woodford Shale source beds.

Les éléments terres rares (ETRs) sont un groupe de 17 métaux aux propriétés voisines comprenant le scandium, l'yttrium, et les 15 lanthanides. Ces éléments sont indispensables à la production de nombreux appareils de haute technologie et incontournables dans le développement des énergies durables. Contrairement à ce que suggère leur appellation, les ETRs sont assez répandus dans la croûte terrestre, alors que leur extraction, à savoir l’extraction liquide-liquide (ELL), est extrêmement difficile, coûteuse et surtout polluante. Afin de fournir une alternative aux procédés industriels, les matériaux mésoporeux à base de silice ont été sollicités à titre d’adsorbant dans l’extraction sur phase solide. Ces matériaux structurés sont intéressants pour l’adsorption d’ETRs puisqu’il est possible d’en modifier simplement la surface avec des ligands adaptés pour l’application voulue. Dans cette thèse, deux séries de ligands à base de structure phthaloyl diamide (PA) et phenylenedioxy diamide (PDDA) ont été synthétisés et greffés sur la surface de matériaux mésoporeux à base de silice KIT-6. Il s’avère, aux vues des résultats obtenus, que ces adsorbants permettent d’extraire sélectivement les éléments de taille différente selon le bite angle du ligand greffé, tandis que la sélectivité n’a pas été observée pour ses analogues homogènes sous la condition de l’extraction liquide-liquide. En plus, les réseaux bimodaux monolithiques qui présentent simultanément des mésopores ainsi que des macropores (pores > 50 nm) sont avantageux, surtout pour l’extraction en conditions dynamiques (en colonne). Les mésopores permettent d’augmenter la surface spécifique du matériau ainsi la surface de contact entre l’agent actif et la solution. Les macropores, quant à eux, améliorent la capacité de transport des fluides, permettant d’éviter l’accumulation des produits et d’ainsi de bloquer les sites actifs. Dans cette étude, des monolithes à base de silice de taille de quelques centimètres ont été obtenus. Après la fonctionnalisation avec le ligand diglycolamide (DGA), les monolithes révèlent des profils de sélectivité exceptionnels envers le Th(IV) dans l’extraction en colonne. La technique concernant les matériaux à empreinte ionique rend possible une sélectivité spécifique. Dans ce cas-ci, la synthèse de matériaux a été réalisée par la co-condensation entre l’organosilane et le précurseur siliceux en présence d’ion Dy3+. Par la suite, la molécule empreinte est enlevée, laissant derrière elle les sites de liaisons et une cavité ayant la forme et la taille du Dy3+. Ainsi, les silices empreintes sont capables de séparer spécifiquement et sélectivement l’ion Dy3+. Dans tous les trois systèmes présentés ici, ces matériaux peuvent aussi être considérés comme étant intéressants pour les applications industrielles, tant en terme de la stabilité sous les conditions d’adsorption testées, que de la sélectivité et de la capacité d'adsorption envers les échantillons de déchets minéraux.
Les éléments terres rares (ETRs) sont un groupe de 17 métaux aux propriétés voisines comprenant le scandium, l'yttrium, et les 15 lanthanides. Ces éléments sont indispensables à la production de nombreux appareils de haute technologie et incontournables dans le développement des énergies durables. Contrairement à ce que suggère leur appellation, les ETRs sont assez répandus dans la croûte terrestre, alors que leur extraction, à savoir l’extraction liquide-liquide (ELL), est extrêmement difficile, coûteuse et surtout polluante. Afin de fournir une alternative aux procédés industriels, les matériaux mésoporeux à base de silice ont été sollicités à titre d’adsorbant dans l’extraction sur phase solide. Ces matériaux structurés sont intéressants pour l’adsorption d’ETRs puisqu’il est possible d’en modifier simplement la surface avec des ligands adaptés pour l’application voulue. Dans cette thèse, deux séries de ligands à base de structure phthaloyl diamide (PA) et phenylenedioxy diamide (PDDA) ont été synthétisés et greffés sur la surface de matériaux mésoporeux à base de silice KIT-6. Il s’avère, aux vues des résultats obtenus, que ces adsorbants permettent d’extraire sélectivement les éléments de taille différente selon le bite angle du ligand greffé, tandis que la sélectivité n’a pas été observée pour ses analogues homogènes sous la condition de l’extraction liquide-liquide. En plus, les réseaux bimodaux monolithiques qui présentent simultanément des mésopores ainsi que des macropores (pores > 50 nm) sont avantageux, surtout pour l’extraction en conditions dynamiques (en colonne). Les mésopores permettent d’augmenter la surface spécifique du matériau ainsi la surface de contact entre l’agent actif et la solution. Les macropores, quant à eux, améliorent la capacité de transport des fluides, permettant d’éviter l’accumulation des produits et d’ainsi de bloquer les sites actifs. Dans cette étude, des monolithes à base de silice de taille de quelques centimètres ont été obtenus. Après la fonctionnalisation avec le ligand diglycolamide (DGA), les monolithes révèlent des profils de sélectivité exceptionnels envers le Th(IV) dans l’extraction en colonne. La technique concernant les matériaux à empreinte ionique rend possible une sélectivité spécifique. Dans ce cas-ci, la synthèse de matériaux a été réalisée par la co-condensation entre l’organosilane et le précurseur siliceux en présence d’ion Dy3+. Par la suite, la molécule empreinte est enlevée, laissant derrière elle les sites de liaisons et une cavité ayant la forme et la taille du Dy3+. Ainsi, les silices empreintes sont capables de séparer spécifiquement et sélectivement l’ion Dy3+. Dans tous les trois systèmes présentés ici, ces matériaux peuvent aussi être considérés comme étant intéressants pour les applications industrielles, tant en terme de la stabilité sous les conditions d’adsorption testées, que de la sélectivité et de la capacité d'adsorption envers les échantillons de déchets minéraux.
Rare Earth Elements (REE) are a group of 17 chemically similar metals that have gained an increasing importance over the past decades, due to their unique properties and many applications in high-tech products. The term “rare” is rather deceptive, since they are quite abundant in the Earth’s crust. However, their extraction and purification can be challenging, and the industrial extraction processes of REEs are often costly and environmentally hazardous. This thesis aims at developing a competitive solid-phase extraction system, based on functional porous silica materials, for the selective extraction of REEs in solution that can be industrially applied. In particular, ordered mesoporous silica (OMS) is a versatile platform that can offer large specific surface area, variety in material structures and morphologies, and stability under applied extraction conditions. Furthermore, the surface properties of OMS allow for easy functionalization with a variety of organic ligands, which largely influence the extraction performance of the sorbents. In this work, the OMS KIT-6 were functionalized by grafting two series of chelating ligands on the silica surface, i.e., preorganized bidentate phthaloyl diamide (PA) ligands and tetradentate phenylenedioxy diamide (PDDA) ligands. By fine-tuning of the bite angles of these chelating ligands, we successfully separated REEs into three categories based on their ionic radius. However, the use of small size particles as packing materials is often associated with a high backpressure of the column, thus limiting their industrial applicability in high flow-rate chromatography analysis. Therefore, the hierarchically structured silicas that contain both macropores (pore size > 50 nm) and mesopores are highly desirable. We report in this work a highly stable silica monolith exhibiting a bimodal, hierarchical macroporous-mesoporous structure for continuous column extraction. Upon grafting of diglycolyl amide (DGA) ligand, the applicability of the column was demonstrated by the removal of Th(IV) from two REE mineral leachates with largely enhanced kinetics and extraction capacity. Finally, in order to further improve the selectivity of sorbents, molecular recognition approach was applied to synthesize highly ordered ion imprinted mesoporous silica (IIMS) through co-condensation using a combination of molecular imprinting technology and traditional OMS, in which dysprosium ion was used as the template. After template removal, the IIMS showed attractive recognition capacity toward Dy3+ from mild acidic solution. Beside the excellent selectivity, in all the three proposed systems, the sorbents were also proven robust and were able to be regenerated for multiple cycle uses, further demonstrating their potential for industrial applications.
Rare Earth Elements (REE) are a group of 17 chemically similar metals that have gained an increasing importance over the past decades, due to their unique properties and many applications in high-tech products. The term “rare” is rather deceptive, since they are quite abundant in the Earth’s crust. However, their extraction and purification can be challenging, and the industrial extraction processes of REEs are often costly and environmentally hazardous. This thesis aims at developing a competitive solid-phase extraction system, based on functional porous silica materials, for the selective extraction of REEs in solution that can be industrially applied. In particular, ordered mesoporous silica (OMS) is a versatile platform that can offer large specific surface area, variety in material structures and morphologies, and stability under applied extraction conditions. Furthermore, the surface properties of OMS allow for easy functionalization with a variety of organic ligands, which largely influence the extraction performance of the sorbents. In this work, the OMS KIT-6 were functionalized by grafting two series of chelating ligands on the silica surface, i.e., preorganized bidentate phthaloyl diamide (PA) ligands and tetradentate phenylenedioxy diamide (PDDA) ligands. By fine-tuning of the bite angles of these chelating ligands, we successfully separated REEs into three categories based on their ionic radius. However, the use of small size particles as packing materials is often associated with a high backpressure of the column, thus limiting their industrial applicability in high flow-rate chromatography analysis. Therefore, the hierarchically structured silicas that contain both macropores (pore size > 50 nm) and mesopores are highly desirable. We report in this work a highly stable silica monolith exhibiting a bimodal, hierarchical macroporous-mesoporous structure for continuous column extraction. Upon grafting of diglycolyl amide (DGA) ligand, the applicability of the column was demonstrated by the removal of Th(IV) from two REE mineral leachates with largely enhanced kinetics and extraction capacity. Finally, in order to further improve the selectivity of sorbents, molecular recognition approach was applied to synthesize highly ordered ion imprinted mesoporous silica (IIMS) through co-condensation using a combination of molecular imprinting technology and traditional OMS, in which dysprosium ion was used as the template. After template removal, the IIMS showed attractive recognition capacity toward Dy3+ from mild acidic solution. Beside the excellent selectivity, in all the three proposed systems, the sorbents were also proven robust and were able to be regenerated for multiple cycle uses, further demonstrating their potential for industrial applications.

Il vino è un prodotto alimentare pregiato, che ha grande influenza nell’economia dei paesi che lo producono. Negli ultimi anni, la produzione vitivinicola Italiana ha subito un significativo aumento nella domanda, a causa dell’apertura di nuovi mercati, stimolando così maggiori canoni di qualità e procedure per la tutela dei vini italiani dalla concorrenza estera. Ne è derivata la necessità di definire marker scientificamente validi e quantificabili. La tesi si occupa: di trasferire i risultati della ricerca di petrografia e geochimica applicata, allo studio dei processi di assimilazione suolo pianta e della territorialità dei prodotti agroalimentari. Questo lavoro, che verte sull’uva, è stato condotto su due aree rappresentative dei principali contesti geologici e geomorfologici della Sicilia Orientale. Si è cercato di identificare, in maniera univoca, le varietà d’uva tramite la concentrazione di Terre Rare, assorbite in varie parti delle piante, prendendo in considerazione sia le caratteristiche del suolo che le condizioni climatiche. La Sicilia vanta una tradizione vitivinicola documentata sin dalla preistoria; sono presenti nel territorio cultivar di grande importanza per il patrimonio agronomico, inoltre, la regione è caratterizzata dalla presenza di differenti litotipi. Nei tre vigneti selezionati delle due macroaree (Etna e Iblei) sono stati scelte sia cultivar a bacca bianca che rossa; per l’area Etnea: Nerl. Cappuccio, Nerl. Mascalese, Merlot, Carricante, Grecanico e Inzolia; per l’area degli Iblei: Cabernet Sauvignon, Frappato, Merlot, Nero d’Avola, Grecanico, Inzolia e Moscato. La scelta è ricaduta su varietà autoctone come il Frappato e il Nero d’Avola, che alloctone come il Merlot e il Cabernet Sauvignon. La prima area è localizzata nel paese di Linguaglossa (Mt. Etna), caratterizzata da suolo vulcanico. La seconda area è localizzata nel paese di Comiso (altopiano Ibleo), caratterizzata da suolo carbonatico; le due tipologie di suolo possiedono concentrazioni di Terre Rare differenti. I risultati, ottenuti dalle varie tipologie di cultivar, mostrano che l’assorbimento di Terre Rare è maggiore nelle piante coltivate negli Iblei, per le maggiori temperature e la scarsa piovosità, così le piante assorbono un grande ammontare di elementi dal suolo. I risultati dimostrano che le Terre Rare sono assorbite e si concentrano soprattutto nelle foglie, e in misura minore nel frutto e dei semi; inoltre, temperatura e piovosità, influiscono sull’assorbimento di Terre Rare dal suolo da parte delle piante. Grazie al contenuto medio di Terre Rare nei campioni, è possibile risalire all’ambiente d’origine delle piante. Le cultivar della stessa area hanno piccole differenze nei pattern delle Terre Rare, nonostante le medesime condizioni climatiche, permettendoci di identificare le cultivar. Se confrontiamo le stesse cultivar cresciute nei diversi ambienti si riscontrano differenze nei pattern che ci permettono di risalire all’ambiente di crescita della pianta.
Wine is a valuable food product, which has a lot of influence in the economy of the countries where it is produced. Over the last few years there has been a significant growth in request of this article by new markets, thus stimulating the quality and procedures for the protection of Italian wines by foreign competition. It has caused the need to establish scientifically valid and quantifiable marker. The thesis is concerned: to transfer results research of petrography and geochemistry applied to the study of ground plant processes assimilation and territoriality of food products. This work, which focuses on grapes, it was conducted on two representative areas of the main geological and geomorphological contexts of Eastern Sicily. We attempted, to get the ways to univocally identify the grape varieties by measuring the concentration of Rare Earths Elements (REEs), absorbed by the parts of the plant during growth, considering the soil and, the climatic conditions. The Sicilian region boasts a winemaking tradition documented since prehistoric times; there are cultivars of great value for heritage agronomist, moreover, the region is characterized by a considerable amount of different lithotypes. In the three selected vineyards of the two macro areas (Etna and Iblei) we were chosen both white and red grapes cultivars; for the area Etnea: Nerl. Cappuccio Nerl. Mascalese, Merlot, Carricante, Grecanico and Inzolia; for the area of the Iblei: Cabernet Sauvignon, Frappato, Merlot, Nero d'Avola, Grecanico, Inzolia and Moscato. We have chosen autochthonous varieties as Nerello Mascalese and Nerello Cappuccio, and allochtonous (Merlot and Cabernet Sauvignon). The first area is located in the municipality of Linguaglossa (Mount Etna); this area is characterized by a volcanic soil. The second area is located in the municipality of Comiso (Hyblaean Plateau) and is characterized by carbonate soil; the soils from two areas showed very different concentrations in REEs. Result obtained on the various types of cultivars showed that the absorption of REEs is higher in grapes grown in Hyblean Plateau, because of the higher temperature and lower rainfall, which make plants to absorb a greater amount of elements from the soil. Results showed that most of REE elements are concentrated in leaves, and at a lesser extent in the fruit and seed; temperature and rainfall, affect the absorption of REEs from the grapevines as well. According to the average content of REEs in different samples you can go back to the environment of origin of the plants. The grape varieties of the same area have different REEs pattern, demonstrating how the behavior of the different grape varieties under the same climatic conditions is different, thus allowing the identification of the various varieties. Same types of cultivars grown in different environments, show different concentrations allowing us to go back to the type of soil on which the plants were grown.

Ni laterites are considered worthy targets for critical metals (CM) exploration as rare earth elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this investigation geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s) (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits. Two Ni laterite profiles from the Falcondo mining area have been compared for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (-50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion. Free grains of PGM with delicate morphologies were discovered in limonite hosted chromitite samples (“floating chromitites”) from highest levels in the Falcondo Ni laterite deposit (Dominican Republic). Textural and chemical evidence obtained via SEM and EMP analysis points to a multistage formation: (i) primary PGM formation at magmatic stage; (ii) transformation to highly porous secondary Os-Ru PGM during serpentinization; (iii) neoformation of Ir-Fe-Ni-(Pt) mineral phases during early stages of lateritization; (iv) neoformation of Pt-(Ir) mineral phases within the critical zone of the profile resulting in nugget shaped accumulation of rounded particulates during late stages of lateritization. The observation of accumulations of most likely biogenic mediated in situ growth of Pt rich nanoparticles in supergene environments could help to explain (i) why Pt bearing nuggets are the most abundant PGM found in surface environments, (ii) why Pt nuggets from placer deposits generally surpass the grain sizes of Pt grains found in parent rocks by several orders of magnitude (few micrometers vs. several millimeters) and (iii) how anthropogenic PGE contamination may affect our biosphere. Osmium chromitite, saprolite and limonite (Falcondo mining area), suggest that serpentinization of the Loma Caribe peridotite has not significantly affected the Re-Os system in Os-rich PGM. This is noted by the fact, that primary PGM formed at magmatic stage and secondary Ru-Os-Mg- isotope characteristics from primary and secondary PGM, separated from Si PGM formed due desulphurization of primary PGM with significant incorporation of Mg silicates, have almost identical Os isotope characteristics, typical of the mantle. However, the Re-Os system can be significantly disturbed during stages of lateritization when porous secondary PGM react with Fe-rich fluids, thus forming hexaferrum and magnetite in the 187 188 interstices of secondary PGM. Here presented data indicate that more radiogenic ratios in higher levels of the weathering profile are linked to steady mobilization of PGE within secondary PGM resulting in subsequent loss of Os counterbalanced by the incorporation of Fe. Os/ Os In this investigation presented data clearly states that PGE are neither noble nor inert in surface environments, at least in those related to tropical Ni laterites from the Northern Caribbean.

The Thor Lake rare-metal (Zr, Nb, Y, REE, Ta, Be, Ga) deposit in the Northwest Territories of Canada represents one of the largest resources of zirconium, niobium, yttrium and the heavy rare earth elements in the world. Much of the potentially economic mineralization was concentrated by magmatic processes. However, there is also evidence of remobilization of Zr, Y and REE by hydrothermal fluids. Geologically, the deposit is situated at the southern edge of the Slave Province of the Canadian Shield, within the 2150 Ma alkaline to peralkaline Blachford Lake Complex (Davidson, 1978).
The rare metal mineralization occurs in two sub-horizontal tabular layers in the Nechalacho deposit, an upper and a lower zone, with Zr hosted primarily by zircon, Nb primarily by ferrocolumbite and fergusonite-(Y), and Y + HREE by fergusonite-(Y) and zircon. The LREE are hosted by monazite-(Ce), allanite-(Ce), bastnäsite-(Ce) and parisite-(Ce)/synchysite-(Ce).
A model is proposed in which REE and HFSE enriched layers were formed by injection of separate miaskitic and agpaitic magmas, to form an upper zone rich in zircon and a lower zone rich in eudialyte. Primary eudialyte was later altered to zircon-fergusonite-(Y)-bastnäsite-(Ce)-parisite-(Ce)/synchysite-(Ce)-allanite-(Ce)-albite-quartz-biotite-fluorite-kutnahorite-hematite-bearing pseudomorphs by an inferred fluorine-enriched magmatic hydrothermal fluid. Yttrium and REE were also mobilized from the cores of primary zircon crystals in the upper zone and locally precipitated as fergusonite-(Y) along micro-fractures. Hydrothermal fluids altered the distribution of REE, within the upper and lower mineralized zones, locally enriching and depleting them, and created a set of secondary minerals which will be the main target of future exploitation.
Le gisement de terres rares (Zr, Nb, Y, REE, Ta, Be, Ga) de Thor Lake situé dans les Territoires du Nord-Ouest, Canada, représente l'une des plus grandes ressources de zircon, niobium, yttrium et des éléments du groupe des terres rares lourdes (REE) au monde. Une partie importante des minéralisations reconnues comme potentiellement économiques résulte de processus magmatiques. Il existe également des évidences d'une remobilisation du Zr, Y et REE par des fluides hydrothermaux. Le gisement se situe sur le versant méridional de la Province de l'Esclave dans le Bouclier canadien, dans les unités de roches alkalines à perakalines du Complexe du lac Blachford datées à 2150 Ma (Davidson, 1978).
La minéralisation de métal rare est associée à deux couches tabulaires sub-horizontales formant une zone supérieure et une zone inférieure. Le Zr est principalement associé au zircon; le Nb à la ferrocolumbite et la fergusonite-(Y); et Y + HREE à la fergusonite-(Y) et au zircon. Les LREE sont quant à eux associés à la monazite-(Ce), l'allanite-(Ce), la bastnäsite-(Ce) et la parisite(Ce)/synchysite-(Ce).
Nous proposons un modèle dans lequel les couches enrichies en REE et HFSE résultent d'injections indépendantes de magmas miaskitique et agpaitique pour former une zone supérieure riche en zircon et une zone inférieure riche en eudialyte. L'eudialyte primaire a été altérée par des fluides hydrothermaux d'origine magmatiques enrichis en fluor et se manifeste comme des pseudomorphes de zircon-fergusonite-(Y)-bastnäsite-(Ce)-parisite-(Ce)/synchysite-(Ce)-allanite-(Ce)-albite-quartz-biotite-fluorite-kutnahorite-hematite. L'yttrium et les REE ont été remobilisés dans des zircons primaires de la zone supérieure et précipités localement en fergusonite-(Y) dans des microfractures. Les fluides hydrothermaux ont affectés la distribution des REE dans les zones minéralisées supérieure et inférieure en les enrichissant et les appauvrissant localement et créant ainsi une suite de minéraux secondaires qui feront l'objet d'une future exploitation.

Rare earth elements, (REE), at ug g⁻¹ levels are used for studies of petrogenisis of different geological materials. For these studies, the REE must be determined precisely. An analytical program was established using an IL 200 Inductively Coupled Plasma, (ICP), spectrometer for the determination of the REE in various matrices, taking into consideration both matrix and spectral interferences, which were found to be severe in some cases. Dissolution of the sample, (0.4-1.0 g), was carried out using two methods; a microwave heated dissolution using a modified commercial microwave oven and a conventional oven heated closed pressure digestion vessel method. The results of these two methods were compared to determine the viability of using the more rapid microwave heated method. Separation of the REE from matrix elements was investigated using three cation exchange resins; Amber lite IR 120 (H), Zeocarb 225 and Dowex 50-WXS. A gradient acid elution method was established using a 15 cm by 20 mm Zeocarb 225 column. The sample was eluted with 140 ml of a 1.5 M H⁺ solution containing 0.75 M Cl⁻ and 0.75 M NO₃⁻, this fraction containing all the matrix elements. The REE were then eluted from the resin with 100 ml of 3 M HNO₃. The REE containing fraction was then reduced to 5 ml, diluted to 10 ml, and analysed for REE content. Liquid-liquid extraction methods for the separation of REE from matrix elements were investigated. It was found that the REE could be extracted synergistically from various buffered aqueous acidic media into chloroform, (CHCl₃), by hexafluoroacetylacetone, (HHFA), and quinoline. Acetylacetone, ( AcAc), was found to react with hexamethylenetetramine, (hexamine), when hexamine was used to buffer the aqueous phase during extraction procedures. The product of this reaction, 3.5-diacetyl-1.4-dihydro-2.6-dimethyl pyridine, was identified using X-ray crystallography.

A novel and simple "constant-addition" technique was used to study calcite precipitation kinetics and the partitioning of REE between calcite overgrowths and their parent seawater solutions under steady state conditions.
As a consequence of solute interactions in solution and at the growing mineral surface, the calcite precipitation mechanism in seawater is complex. It is dominated by the following reversible overall reaction: $ rm Ca sp{2+}+CO sbsp{3}{2-} rightleftharpoons CaCO sb3.$ A kinetic expression is proposed which describes the precipitation rate according to this reaction. A partial reaction order of 3 with respect to CO$ sb3 sp{2-}$ is obtained.
REE have a strong affinity for calcite and substitute for Ca$ sp{2+}$. REE partition coefficients in calcite overgrowths were calculated from their concentrations in the overgrowths and their parent solutions using a non-thermodynamic homogeneous model. The concentrations were determined by chelation and gradient ion chromatography (CGIC) using a revised procedure. REE partition coefficients decrease gradually with increasing REE atomic number. They are sensitive to changes in (REE): (Ca$ sp{2+}$) and the presence of O$ sb2$ in solution, but unaffected by the precipitation rate, $ rm lbrack CO sb3 sp{2-} rbrack$ or Pco$ sb2$ of the solution. The partitioning behaviour of REE is negatively correlated to the solubility of their respective carbonates and influenced by speciation, adsorption, and subsequent surface reactions (e.g., dehydration).

This study documents the magmatic, hydrothermal and supergene mineralogy and geochemistry of phosphorus and rare earth elements in carbonatite complexes using examples from Tundulu (Malawi), Sokli (Finland), Siilinjarvi (Finland) and Kaluwe (Zambia). In carbonatites, phosphorus averages 1-2% P20S and forms the minerals fluorapatite and monazite. Hydrothermal and supergene processes enrich fluorapatite in Na and REEs through vitusite-type exchanges which lead to formation of vitusite, belovite and britholite; and in CO2 through anti-francolite substitutions. The highest rare earth element contents are found in late-stage ankerite carbonatites or similar rocks of low temperature origin (T < S(XtC) and in hydrothermally altered rocks, where they occur mainly as fluorocarbonates or carbonates. Such minerals are consistent with the REEs having been transported in form of mixed fluoride-carbonate complexes. The mineral paragenesis in hydrothermal veins suggests that different fluorocarbonates precipitated depending on the activity of Ca supplied to the fluid by the wall rocks. The various minerals are modelled to form by simple combinations of calcite (CaCO:v and bastnaesite (REEC03F) molecules. A secondary characteristic feature of these reactions is that extreme heavy rare earth enrichment occurs if the wall rocks are apatite-rich. Petrogenetic modelling using REEs suggests that carbonatites are unlikely to be derived from carbonated silicate magmas by fractional crystallisation or liquid immiscibility. These findings are supported by ex solution temperatures of about 9S0·C recorded using the calcitedolomite geothermometer for quenched lapilli from the Kaluwe carbonatite.

Coal has been an important natural resource of energy in the Illinois Basin for generations. In addition to the organic macerals in coal, there is inorganic matter containing minerals and trace elements. With growing demand for economic and critical metals including Rare Earth Elements and Yttrium (REY), coals containing anomalously high concentrations of trace elements, as well as their associated coal mine wastes, and drainages have been explored as promising secondary resources, but there were no former studies of REY in Illinois basin CMD. CMD samples were collected from 35 abandoned coal mine sites from three regions of the Illinois basin. Region 1 (R1) the southern extent of the basin extending west along the cottage grove fault system and includes Hicks dome, a nexus of regional hydrothermal activity and provenance of the Illinois Kentucky Fluorite District (IKFD) ore deposits; Region 2 (R2) comprised locations situated in western Illinois along the Du Quoin Monocline; and Region 3 (R3) comprised locations situated in northern Illinois, farthest from the Hicks Dome. Two hypotheses were tested in this study: (1) that pH and ΣREY would share an inverse correlation, with the greatest abundances of REY found in the most acidic drainages; and (2) hydrothermal activity associated with Hicks Dome in southern Illinois was the source of REY enrichment in the coals, and so, REY abundance and pattern would reflect proximity to the cryptoexplosive complex, with the greatest enrichments expected in R1, closest to Hicks Dome. The geochemical data of 42 CMD samples was examined was analyzed to test these two ii hypotheses. Samples ranged from extremely acidic (pH=1.93) to circumneutral (pH=7.6) with an average pH value of 3.4. Total REY values (ΣREY) averaged 1,057 μg/L across all samples and ranged from 0.4-9,879 μg/L while Σcritical-REY abundances (Nd, Eu, Tb, Dy, and Y) averaged 611 μg/L and ranged from 0.2-7,213 μg/L. Furthermore, there are significant direct correlations of ΣREY with Al, Si, SO4, Zn, Ni, Cu, Cd, Co and no correlations with Fe, Ca, P, Ba, and V. In the course of investigation, it was found that pH and linear concentration values for REY correlate poorly. However, logarithmic values of REY concentrations (i.e., log[ΣREY]), as well as the above trace metals have strong inverse correlations with pH( (r=- 0.84, p

Rare Earth Element (REE) determination in samples of coal and fly ash was undertaken by gradient high performance ion chromatography (HPIC). Ion chromatographic analysis requires that samples be in solution and that the matrix transition metals be removed. Coal samples, weighing 0.20g, were successfully dissolved in sealed pressure vessels in a microwave oven. Standard ashing procedures, followed by acid dissolution, were carried out to allow comparison with the microwave digestion technique. A lithium metaborate/tetraborate fusion and acid dissolution technique was used for the dissolution of fly ash. For the technique of REE determination the sample matrix was removed by off-line cation exchange. In an initial stage of the HPIC analysis the transition metals were removed by anion exchange using pyridine-2,6 dicarboxylic acid. The REE were then analysed using gradient elution of oxalic and diglycolic acid. Typically a 100μ1 volume of sample solution was employed for REE determination, but in the case of low ash (low REE) coal samples, prepared by microwave digestion, on-line concentration of 3-5 ml of sample, was necessary. The separated REE were reacted with 4-(2-pyridylazo)-resorcinol (PAR) and detected photometrically using a visible light detector at a wavelength of 520nm. Reproducibility for each REE was typically better than 5%CoV. Results from the analysis of coal and fly ash international standard reference materials were in acceptable agreement with values from alternative analytical procedures. Smooth, coherent trends obtained when the data were plotted on chondrite and "shale composite" normalised diagrams provided some support for the accuracy of the technique. The application of HPIC to the determination of REE in coals was demonstrated by the analysis of a new international reference coal sample, USGS CLB-1. Differences in REE concentrations between coal samples prepared by microwave digestion and ashing were observed. The HPIC analytical technique was also applied to the determination of REE in fly ash. The REE concentrations of fly ash from sequential electrostatic precipitators, from Lethabo and Kendal power stations, were determined to elucidate the behaviour of REE after the combustion of coal. REE concentrations increased through the sequential precipitators.

The rare earth elements (REE) are increasingly important in a variety of science and economic fields, including (bio) geosciences, paleoecology, astrobiology, and mining. However, REE distribution in early rock-microbe-plant systems has remained elusive. We tested the hypothesis that REE masspartitioning during incipient weathering of basalt, rhyolite, granite and schist depends on the activity of microbes, vascular plants (Buffalo grass), and arbuscular mycorrhiza. Pore-water element abundances revealed a rapid transition from abiotic to biotic signatures of weathering, the latter associated with smaller aqueous loss and larger plant uptake. Abiotic dissolution was 39% of total denudation in plantmicrobes- mycorrhiza treatment. Microbes incremented denudation, particularly in rhyolite, and this resulted in decreased bioavailable solid pools in this rock. Total mobilization (aqueous + uptake) was ten times greater in planted compared to abiotic treatments, REE masses in plant generally exceeding those in water. Larger plants increased bioavailable solid pools, consistent with enhanced soil genesis. Mycorrhiza generally had a positive effect on total mobilization. The main mechanism behind incipient REE weathering was carbonation enhanced by biotic respiration, the denudation patterns being largely dictated by mineralogy. A consistent biotic signature was observed in La: phosphate and mobilization: solid pool ratios, and in the pattern of denudation and uptake.

This thesis consists of three main chapters preceded by an introduction that discusses the importance of diffusion in minerals to constrain the geochemistry of various magmatic processes. The first chapter deals with the experimental technique and measurement of tracer element diffusion data in garnet and clinopyroxene. Self-diffusion coefficients of selected REE have been measured as a function of temperature (770°C-1050°) at 1 bar and oxygen fugacity (fO₂) corresponding to that defined by the iron-wustite buffer. The experimental results indicate small variations of diffusivity for REE in both garnet and clinopyroxene and an activation energy which is similar to the activation energy for diffusion of major components. In the second chapter the atomistic mechanism of Nd diffusion in garnet is investigated by molecular dynamics (MD) simulation. An optimization procedure based on genetic algorithm provides the semi-empirical coefficients that are used to reproduce the repulsive forces between atoms. Results from MD simulations at high pressure and temperature show that Schottky defect is the most favorable mechanism for vacancy formation in the intrinsic region. The preferred reaction to incorporate neodymium in the dodecahedral site involves transferring an iron atom to the octahedral site after removing the aluminum atom from the lattice site. A model of diffusion in the extrinsic region with a prescribed vacancy defect fraction in the garnet (10⁻⁴) also provides an acceptable result. The third chapter considers some of the potential applications of the REE diffusion data in garnet and clinopyroxene to magmatic processes. REE patterns obtained from the solution of a moving boundary problem shows that incompatible elements are more sensitive to disequilibration controlled by diffusion. Melt generated by disequilibrium melting is less enriched in incompatible elements than melt produced by an equilibrium melting process. Solution of a multiphase flow model, including the chemical transport equations with diffusion in a solid phase, permits a more realistic investigation of the disequilibrium melting process. During the ridge evolution the model predicts negligible effect of solid state diffusion on the geochemical evolution of the partial melt and the residual solid.

Micrometer-thin rims of hydrothermally altered zircon preserve significant geological information regarding the timing and nature of fluid infiltration. The research presented in this thesis details an investigation of the isotopic and geochemical composition zircon rims from deformed Archean meta-sedimentary rocks proximal to the world class Musselwhite gold deposit. A continuous ablation Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb technique is proposed in conjunction with Secondary Ion Mass Spectrometry (SIMS) U-Pb and LA-ICP-MS REE depth profile methods. These techniques are capable of identifying and analyzing isotopic and chemical modification of zircon rims that are <5 μm thick by ablating directly into the surface of unpolished crystals. The age of analyzed rims is >100 m.y younger than crystal interiors and corresponds to periods of regional magmatism and hydrothermal activity. The measured thickness of rims is variable across single grains and between grain suites suggesting that they do not form as a uniform mantle around the crystal interior. Instead the interacting fluids exploit pre-existing structural weaknesses caused by sedimentary transport and the α-decay of uranium. A novel LA-ICP-MS single element grain 2-dimension mapping technique for unpolished zircon demonstrates preferential element mobility along fractures and in isolated patches. Pressure-temperature experiments were conducted on a zircon reference material under lower greenschist facies conditions to better understand the low temperature incorporation of REEs into the zircon structure. LA-ICP-MS element mapping of unpolished grains reveals that zircon are chemically modified under these conditions, as characterized by an increase in Ce and Y concentration (up to an order of magnitude enrichment) in CePO4-bearing and YPO4-bearing experiments, respectively, when compared with the concentrations of unaltered primary grains. The integration of these micro-analytical techniques on unpolished zircon can provide insight into the timing of low- to moderate-temperature history of supracrustal rocks which would remain otherwise undefined.

One of the largest environmental liabilities facing the Canadian and international mining industry includes the effects of acidic drainage to water resources. This thesis sought to determine biogeochemical mechanisms of rare earth element and yttrium (REY) enrichment in mine drainage, linkages between REYs and microbial populations, and whether REYs were present in water or biofilm at mineable quantities or toxic levels. Water and co-occurring biofilm samples were collected from North and South American mining and control sites, and a passive water treatment system in Pennsylvania. REY concentrations within mineralized biofilm were observed to occur at borderline mineable quantities within biofilm in coal mine drainage (1,000 mg/kg dry weight total REYs), where REYs were bound predominately to particulate organic matter, manganese and iron, limiting their bioavailability. Within the passive treatment system, REYs showed the greatest maximum water-biofilm partitioning coefficients after Al and Fe, and a strong inverse relationship with aqueous REY concentration. Photosynthetic eukaryotes were observed to occur within biofilms that contained an abundance of neutrophilic iron oxidizing bacteria.

Three phases of work were performed for this study. First a new form of liberation analysis was created and applied to two coal samples from separate formations. This new method of liberation analysis attempts to remove sources of error found in the traditional form of liberation analysis. This new method is capable of producing results comparable to multiple iterations of the traditional liberation analysis while using only one head sample. The new method relies on the mathematical reconstruction of the data to produce the resulting liberation profile. This allows the user to easily expand the method to include more liberation profiles without greatly increasing the amount of head weight needed. The results of this phase confirm that the products of each liberation profile reconstitute the correct feed ash. The second phase of work focused on the evaluation and concentration of rare earth elements (REEs) present in the refuse streams of coal processing plants found in the eastern United States. Twenty plants were sampled for the fleet study. Samples of these plants' refuse streams were collected and their REE and ash contents were determined. Coal from the Eagle seam, Fire Clay seam, and Fire Clay Rider were collected and tested during the concentration phase. Samples of a waste coal from the Pittsburgh seam and a coal combustion by prodcut were also provided by a third party. The separation methods investigated include multi-gravity separation, electrostatic separation, and selective oil agglomeration. Partition curves from x-ray sorting devices were also applied to REE float-sink data as well. The results of this work show that REEs tend to partition with low ash material when viewing the results on an ash basis. Finally, the third phase of this work involved the application of x-ray sorting technology on different coals. This work showed that the x-ray sorting technology in question is capable of effectively treating prescreened feed with a size range of 2" x 1/4". The work also shows that the x-ray sorting technology also has applications in the power generation field, where it can be used to eliminate elements of environmental concern.
Ph. D.

Rare Earth elements (REEs) are economically important due to their critical applications within multiple industries. This study investigates the Spruce Pine district of North Carolina, testing the economic feasibility of repurposing current mine waste tailings as a rare earth element resource. Spruce Pine is home to several active quartz and feldspar mining operations, with large waste tailing piles generated during the separation process for quartz and feldspar. The mineralogy, composition, and REE budget of the tailings was examined to assess the economic viability of rare earth element extraction. The local geology includes a series of muscovite class pegmatites of Devonian age (390 Ma), intruded into the primarily amphibolite-grade units of the Ashe and Alligator Back formations (Wood, 1996). The waste tailing piles of two on-going quartz mining operations were sampled to evaluate the potential economic feasibility of rare earth element extraction from key accessory phases, including apatite, remaining from the initial separation process. Sample characterization utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence (XRF), energy-dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD). The results of this investigation support the conclusion that, at the current recovery rate, price of rare earth elements, and cost of refinement, economic recovery of REE from the studied tailings is not viable. However, yttrium and dysprosium offer the highest potential for economic recovery. If some combination of improvements to the extraction process, reduction in refinement cost, or increases in price occur, yttrium and dysprosium are sufficiently abundant that extraction could become economically viable.
Master of Science
Rare Earth elements (REEs) are comprised of the Lanthanide series of elements as well as yttrium and scandium. REEs are economically important due to their critical applications within multiple industries. Current uses include electronics, magnets, lasers, electric motors, optical fibers, nuclear reactor control rods, visual displays, etc. Although the demand for REEs is high, the current sourcing of REEs is quite scarce. This study investigates the Spruce Pine district of North Carolina, testing the economic feasibility of repurposing current mine waste tailings as a rare earth element resource. Spruce Pine is home to several active quartz and feldspar mining operations, with large waste tailing piles generated during the separation process for quartz and feldspar. The mineralogy, composition and REE budget of the tailings was examined to assess the economic viability of rare earth element extraction. The waste tailing piles of two on-going quartz mining operations were sampled to evaluate the potential economic feasibility of rare earth element extraction from key accessory phases, including apatite, remaining from the initial separation process. The results of this investigation support the conclusion that, at the current recovery rate, price of rare earth elements, and cost of refinement, economic recovery of REE from the studied tailings is not viable. However, yttrium and dysprosium offer the highest potential for economic recovery. If some combination of improvements to the extraction process, reduction in cost of refinement, or increase in price were to occur, yttrium and dysprosium are sufficiently abundant that extraction could become economically viable.

Geology
M.S.
Concentrations of rare earth (REE), U, Th, and other trace elements (TE) were measured using LA-ICP-MS along transects across five Late Eocene brontothere bones from the terrestrial Late Eocene Chadron Formation of Nebraska and four Miocene marine mammals from the Atlantic Coastal Plain. Samples were analyzed to determine REE diffusion periods, and to determine if histological factors affect post mortem uptake of REE/TE. In terrestrial fossil bones, concentrations of REE are highest at the bone surface and decrease with depth into the trabecular bone, consistent with diffusion-limited models. Histology may affect REE incorporation. An outer circumferential layer (OCL) is preserved along the outer 1 mm of the brontothere rib (F08-10) and femur (F08-09). REE concentrations in the OCL are much lower than in the underlying bone, indicating either lower incorporation or post fossilization leaching. REE concentrations are sometimes elevated in trabecular bone and Haversian systems, which may act as secondary diffusion pathways. REE concentration gradients are generally steeper in marine fossils than in terrestrial fossil bones, indicating longer periods of REE uptake in terrestrial fossils. Calculated periods of diffusion in terrestrial environments are 2.2 +/- 0.5 to 54.8 +/- 1.5 ka (based on a wetness factor of 0.5 +/- 0.1). Periods of diffusion for marine environments range from ca. 0.9 +/- 0.2 to 2.8 +/- 0.6 ka. However, within some terrestrial samples U is introduced into the bone over a much longer time span, possibly as a function of fluctuating redox conditions. If these values are representative, diffusion-fossilization periods are shorter in marine/lacustrine/spring/channel environments due to constant water saturation. Saturation of a bone during diffusion may also affect the morphology of REE signatures within the bone. In terrestrial bones, REE are strongly fractionated with depth, producing signatures varying from light-REE enriched at the surface to middle-REE depleted at depth. However, depth fractionation of REE is much less pronounced in marine bones, which may result from the introduction of fluid unreactive. These differences in REE fractionation are consistent with a greater influence of multiple secondary REE/TE diffusion paths in marine samples. Periods of diffusion for terrestrial samples differed within a single bonebed accumulation (2.2 +/- 0.5 to 54.8 +/- 1.5 ka). However, REE signatures are internally consistent with one another within the bonebed indicating that groundwater chemistry did vary during fossilization. If groundwater chemistry changes during diffusion, bone could be recording different signals, which has implications for using post-mortem REE/TE/Isotopes for paleoenvironmental reconstruction. Previous studies of soft tissue preservation in fossilized bone have inferred shorter periods of diffusion and suggested that the rate of diffusion must outpace the rate of decay. Diffusion periods in bone from well drained terrestrial settings are too long to preserve soft tissue. However, periods of diffusion in marine fossil bones are much shorter, suggesting the possibility for bio-molecule preservation.
Temple University--Theses

The Mount Vulture basin is one of the most important aquifers for drinking water and irrigation supply in southern Italy. The volcanic aquifer mainly consists of pyroclastic and subordinate lava flow layers. Aim of this study is to investigate for the first time the REEs’ geochemical behaviour in the Mount Vulture groundwater assessing concentrations and fractionation patterns and performing speciation calculation, in order to verify whether REEs’ geochemistry records the geochemical processes occurring in this aquatic system. The study will also discuss the flow system of the groundwater’s basin and possible controls on the REEs’ distribution along the studied groundwater flow paths in the Mt Vulture. The water samples were collected from springs and drilled wells during a field trip in the dry season to record the highest concentration of dissolved elements. A cluster analysis highlights the existence of two main subsets: a high EC (HEC, average EC = 2,495 µs/cm) subset with lower pH (average = 6.12), Eh (average = 421 mV), and DO (average = 2.48 µmol/kg), and higher T (average = 18.7 °C) values; and a low EC (LEC, average EC = 382 µs/cm) characterised by higher pH (average = 6.50), Eh (average = 543 mV), and DO (average = 7.31 µmol/kg), and lower T values (average = 15.4 °C). In the HEC subset, the Na+ and HCO3- are significantly higher (Na+ average = 410.7 mg/l, HCO3- average = 1176.6 mg/l) than in the LEC subset (Na+ average = 31.7 mg/l, HCO3- average = 198.6 mg/l). That suggests that the HEC and LEC waters correspond roughly to the waters from the discharge zone and recharge zone, respectively. Overall, the groundwater exhibited REE concentrations well below 1000 ng/l, and the average content measured in the discharge water is approximately three times higher than that of the recharge water. In the recharge water, the shale normalised patterns are characterised by a more negative average Ce anomaly (logCe*PAAS = −0.56), a more positive average Eu anomaly (logEu*PAAS = 0.75), and a larger average (La/Yb)PAAS (log(La/Yb)PAAS =−0.12). The observed relationship between Ce anomalies (Ce*) and dissolved oxygen (DO) supports the idea that Ce oxidative scavenging, probably involving Fe/Mn oxyhydroxides, has a role in determining the size and shape of the Ce*. Further, the less negative average size of the Ce* in the discharge zone also suggests desorption of Ce as Ce3+, according to previous findings on the content of dissolved Fe and Mn. The desorption is related to changes in redox conditions, according to the lower Eh and DO average values observed in the discharge zone compared to the recharge zone. The lack of a significant correlation between Eh and Ce anomalies indicates that, in addition to the aqueous chemistry, the source composition affects Ce*. Although a significant correlation is observed between Eu anomalies (Eu*) and Eh and DO, the strongly reducing condition promoting Eu3+ and Eu2+ is never attained in the Mt. Vulture aquifer. The largest Eu* are associated with the recharge zone where the average Eh and DO values are higher. The volcanics occurring in the Mt. Vulture lithologies are characterised by PAAS-normalised patterns with positive Eu anomalies due to the presence of feldspars. This constraint indicates that, in the recharge zone, the size and shape of the Eu* of groundwater are largely due to the dissolution of feldspars. In the discharge zone, most samples are in equilibrium in terms of smectite content, and Eu2+ adsorption onto the clay phase surface or its inclusion in the mineral structure as an exchangeable cation, due to vicariance with Ca2+ and Sr2+, could explain the smaller average size of the Eu anomaly. Further, the occurrence of secondary minerals preferentially scavenging LREE also explains the difference in the LREE/HREE fractionation, indicated by the (La/Yb)PAAS index and observed between the recharge and discharge zones. Finally, speciation calculations reveal that dissolved REEs consist mainly of carbonato complexes (LnCO3+), whereas the percentage of the dicarbonato complexes (Ln(CO3)2-) increases in samples with circa-neutral pH. At acidic pH, the Ln3+ species are important, and, in the samples from discharge zone affected by a large amount of dissolved sulphate derived by feldspathoids dissolution, the percentage of LnSO4+ species is not negligible. Overall the REEs’ distribution in the Mt. Vulture aquifer is originated by several mechanisms, including weathering reactions involving volcanic rocks, the occurrence of secondary minerals, and pH and redox control. Therefore, the REEs’ geochemistry is a powerful tool in assessing the geochemical processes affecting the groundwater environment.