Rare earth elements are the 14 lanthanides on the periodic table, plus yttrium and scandium. These elements play a critical role in modern-day technologies such as liquid-crystal displays, GPS systems, and fiber optic cables. A majority of the mining of these elements is from China; however, due to decreasing reserves a need for alternative processes for extracting and processing rare earth elements (REEs) is becoming increasingly important. Special focus has been placed upon the identification of REEs within coal refuse, but the phase designation and speciation is not fully understood. This investigation focuses on the characterization, speciation, and morphology of REEs within fine and coarse coal refuse. During this study, physical and chemical characterization was conducted on coal refuse samples to understand characteristics, which influence REE phase designation. Experimental methods were chosen to specifically evaluate REE content and speciation across four key characteristics: size distribution, density, seam location, and thermal decomposition. Characterization of the refuse material was conducted in two campaigns: (1) an exploratory campaign, which focused on size distribution, and physical imaging of REEs within fine refuse, and (2) a detailed campaign, which utilized sequential chemical extraction methods alongside calcination to understand the phases in which REEs are present in coarse refuse. The results show that REEs within fine coal refuse are smaller than ten microns and found with phosphorus. In general, as size decreased REE content increased, likely due to increased clay content. Further conclusion could not be drawn from simple microscopic analysis. Consequently, detailed chemical characterization was conducted to fully understand REE speciation. The tests showed that a majority of REEs within coarse refuse were within insoluble species. A calcination treatment was found to greatly increase the recovery of REEs from the metal oxide fraction, thus increasing the overall soluble species contained within the coarse refuse material. / Master of Science / Due to increasing global demand and limited reserves, alternative sources for rare earth elements (REEs) have become an increasingly important research topic. REEs are a vital component of many modern technologies, including GPS systems, fiber optic cables, and LCD screens. Current mining of REEs is primarily from Chinese reserves which are becoming increasing depleted and are not strictly regulated for environmental impact. Due to these challenges, other resources of REEs are of increasing importance. Prior research has found coal and associated byproducts to have concentrations of REEs that could be economically exploited, reducing the rate of depletion of REE resources worldwide. To develop more efficient and cost-effective processing methods, fundamental information on the mineral composition of REE-bearing materials is needed. With this information, engineers can develop better processes that can specifically target REE-containing minerals while maximizing economic and environmental outcomes. This research seeks to overcome this knowledge gap through advanced material characterization and well-controlled laboratory process testing of coal refuse. The results show that REEs typically congregate in specific material fractions (e.g. fine size, moderate density), and these materials can be readily transformed through simple heat treatment. This transformation greatly improves the processability and provides a pathway for the economic recovery of REEs from coal wastes. The further development and deployment of these technologies can have societal benefits such as: more jobs, reduced reliance on foreign sources, and environmental cleanup of current coal waste deposits.

This study considered the geology, mineralogy, geochemistry, formation and evolution of the heavy rare earth element (HREE) mineralised Lofdal alkaline carbonatite complex (LACC), which is located on the Bergville and Lofdal farms northwest of Khorixas, in the Kunene Region of the Republic of Namibia. . Field methods used included mapping, ground and hyperspectral airborne geophysics, and sampling. Analytical techniques used were optical petrography and CL, XRF, ICP-AES, backscattered and secondary electron imaging, electron microprobe, LA-ICP-MS, leaching, as well as carbon and oxygen stable isotope determination. The LACC comprises a swarm of dykes, mainly calcite carbonatite but also dolomite and ankerite carbonatite dykes (classified into five types) and two newly discovered plugs of calcite carbonatite (‘Main’ and ‘Emanya’), with associated dykes and plugs of phonolites, syenites and rare mafic rocks. These all intrude into the Huab Metamorphic Complex basement rocks within a NE-SW shear zone over 30 km long. The main HREE host mineral is xenotime-(Y). It occurs in highly oxidised iron-rich calcite carbonatite dykes mantling and replacing zircon, associated with hematite, thorite and apatite, or associated with monazite-(Ce), synchysite-(Ce), and parisite-(Ce), replacing the fluorocarbonates; it also forms aggregates in ankerite carbonatite. Although xenotime-(Y) occurs throughout the paragenetic sequence, there is much evidence for hydrothermal fluid activity at Lofdal, altering the dykes, and taking xenotime-(Y) into brecciated carbonate veins in albitised country rock (fenite). Radiogenic (Sr, Nd-Sm, U-Pb) and C and O stable isotope studies confirm that the carbonatite, derived from an enriched mantle, is the source of the REE. Mineralisation was contemporaneous with carbonatite emplacement at 765 ±16 Ma. Magmatic fluids >300°C were diluted with cool meteoric fluids. Abundant fluorite and carbonate indicate roles for F- and CO32- in addition to Cl- in REE transport. These ligands form the most stable complexes with HREE and since xenotime is soluble in concentrated alkali halide solutions, they could have preferentially transported and then deposited xenotime. Many of the features of Lofdal are common to other REE-rich carbonatite complexes but the xenotime-(Y) abundance is so far unique. The high amount of fluid activity in shear zones around the dyke swarm and probably a higher proportion of HREE in the original magmas seem to be the main differentiating features.

Niobium and rare earth elements (REE) are considered as strategic metals in industrialised countries, and are mainly derived from carbonatite-related deposits. Indicator mineral methods for carbonatites using of portable XRF and Quantitative Evaluation of Materials by Scanning Electron Microscopy (QEMSCAN®), shows promise in exploration for Nb and REE. Portable XRF analysis of stream sediments from the Aley, Lonnie, and Wicheeda carbonatites identified 125-250 μm as the ideal size fraction for indicator mineral studies. QEMSCAN® provides (with no additional processing) detection and characterisation of indicator minerals (when found in high concentrations) from carbonatite deposits. Preconcentration by Mozley C800 separator is recommended for sediment samples with low concentrations of indicator minerals. Discrimination diagrams for pyrochlore supergroup and columbite-tantalite series minerals show that minerals from carbonatites occupy the pyrochlore field and extend slightly into the betafite field. Columbite-tantalite series minerals from carbonatites have Mn/(Mn+Fe) atomic ratios ≤0.25 and Ta/(Ta+Nb) ≤0.20. The compositional fields for pyrochlore supergroup and colubmite-tanatlite series minerals from different deposit types partially overlap. / Graduate / 0996 / 0411 / 0372

This thesis focuses on the geochemistry of secondary minerals, mainly calcite but also others such as fluorite and Ca/Al silicates, precipitated throughout the last 1.5 billion years in fractures of crystalline rock, SE Sweden. The work was based on previous reconnaissance studies and has been possible thanks to access to high-quality drill cores and associated mapping data provided by the Swedish Nuclear Fuel and Waste Management Co (SKB). Concentrations of rare earth elements (REEs) and occasionally other metals were determined in a variety of secondary minerals from fractures (mainly open systems) and veins (mainly sealed systems) and in primary minerals from the bedrock. Stable-isotope composition was measured in the secondary minerals. The overall aim was to define the sources, uptake and fractionation of REEs in calcite, and a few other co-genetic minerals, precipitated throughout the geological history under conditions ranging from hydrothermal to low temperatures. Collectively, the findings of the individual studies show that there is no easy and straightforward control of REE abundance and fractionation in calcite and other minerals in fractures and veins in crystalline bedrock settings. For example, the REE features in calcite vary extensively within sub-generations of single vein-precipitating events, on micro scale in transects across individual veins, and unsystematically over the geological history characterised by successively decreasing temperatures of mineral formation. Although the REE content in, and release from, the crystalline bedrock can have an influence on REE distribution in calcite and other minerals, it is of overall minor importance within a given bedrock domain. The main advantage of determining REEs in secondary minerals in fractures and veins in crystalline rock is therefore, as revealed in this work, to assess the character and evolution of the conditions (including features of the paleofluids) during confined mineral-precipitating events.

Biosurfactants are compounds that exhibit surface activity (e.g., reduce surface and interfacial tension) and are derived from natural, biological sources. They are considered green substances due to their natural derivation, biodegradability, and relatively low toxicity. Biosurfactants from multiple classes have been shown to interact with metals, and a review of these interactions is provided. Rhamnolipids produced by Pseudomonas aeruginosa are attracting attention for metal remediation applications. The purpose of this dissertation is to evaluate rhamnolipids' ability to complex rare earth elements, determine the environmental compatibility of novel rhamnolipid diastereomers, and assess the efficacy of rhamnolipid as a collector in ion flotation. Previous research shows rhamnolipids selectively bind elements of environmental concern over common soil and water cations, but there had been no examination of transition metals from the f-block of the periodic table. The f-block elements include the rare earth elements, which are a vital component of nearly every modern technology and subject to supply risk. The interaction between monorhamnolipids and the rare earth elements was investigated by determining conditional stability constants using a resin-based ion exchange method. For the 27 metals examined, the conditional stability constants could be divided into three groups, albeit somewhat subjectively: weakly, moderately, and strongly bound. UO22+, Eu3+, Nd3+, Tb3+, Dy3+, La3+, Cu2+, Al3+, Pb2+, Y3+, Pr3+, and Lu3+are strongly bound with conditional stability constants ranging from 9.82 to 8.20; Cd2+, In3+, Zn2+, Fe3+, Hg2+, and Ca2+ are moderately bound with stability constants ranging from 7.17 to 4.10; and Sr2+, Co2+, Ni2+, UO22+, Cs+, Ba2+, Mn2+, Mg2+, Rb+, and K+ are weakly bound with stability constants ranging from 3.95 to 0.96. The uranyl ion is reported twice due to the ion demonstrating two distinct binding regions. The conditional stability constants were demonstrated to be an effective predictor of metal removal order. The metal parameters of enthalpy of hydration and ionic charge to radius ratio were shown to be determinants of complexation strength. Naturally produced rhamnolipids are a mixture of congeners. Synthetic rhamnolipid synthesis has recently enabled production of four monorhamnolipid diastereomers of a single congener. The biodegradability, acute toxicity (Microtox assay), embryo toxicity (Zebrafish assay), and metal binding capacity of the diastereomers was investigated and compared to natural monorhamnolipid. Biodegradability testing showed all the diastereomers were inherently biodegradable. By the Microtox assay, all of the monorhamnolipids were categorized as slightly toxic by Environmental Protection Agency ecotoxicity categories. Out of 22 parameters tested, the zebrafish toxicity assay showed only diastereomer toxicity for the mortality parameter, except for diastereomer R,R which showed no toxic effects. All the monorhamnolipids interacted with both Cd2+ and Pb2+. Ion flotation is one possible technology for metal recovery and remediation of metal contaminated waters. Ion flotation utilizes charged surfactants to collect and concentrate non-surface active ions at the surface of an aerated solution. Rhamnolipid's suitability as a collector in ion flotation was investigated. A flotation column was designed to test monorhamnolipid efficacy as a collector. Monorhamnolipids form foams and effectively remove Cs+, Cd2+, and La3+ from solution. The efficacy of the flotation process relies on the collector:colligend ratio and valency of the colligend. Flotation of metal solutions showed a removal order of Cd2+>La3+>>Cs+ when the metals were present individually and mixed at equimolar concentrations. When mixed at order of magnitude different concentrations, the flotation order was Cd2+>>Cs+>>La3+. These studies show rhamnolipid has potential to be used for environmentally-compatible metal recovery and metalliferous water remediation, especially for the rare earth elements.

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.

Rare earth elements (REE) are an increasingly important group of metals due to their role in the development of modern technologies. Despite being abundant within the Earth’s crust recoverable ores are uncommon, and their mineralization isn’t as well understood as other abundant ore types. In this work, the mineralization of REE occurring in outcrop samples at Hicks Dome, a cryptoexplosive feature that resides in the Wauboukigou Alnöite Province in southeastern Illinois, was studied to determine the mode of mineralization and the origin of the REE. Xenotime-(Y) was identified with a scanning electron microscope in an intrusive breccia and emplaced during or shortly after the uplift which created the oval doming of the Paleozoic section. Whole rock REE concentrations from ultramafic dikes at Hicks Dome closely match global averages of lamprophyres and carbonatites, with a steep La to Lu slope, and enrichment of light rare earth elements. Hicks Dome has unique characteristics relative to the other intrusions in the Province, such as elevated REE, Th, and doming. These traits indicate that the dome was more closely related to an intrusive body at depth that sourced heat, volatile gases, and a suite of rare elements. Based on these data, the REE mineralization and thorium associated with the siliceous breccia is directly related to the alkaline ultramafic intrusion at Hicks Dome. The volatile rich, hot fluids emanating from the ultramafic magma supplied REE and thorium were mixed with the regional fluids responsible for the IKFD.

More resources are being defined as critical, which can be attributed to the linear economy of ‘take, make and dispose’. An alternative is to implement the circular economy (CE) which could reduce several negative effects, among other things resource depletion. The aim of this thesis is to identify what current sustainability indicators are lacking to assess a resource with the CE concept. This is done by developing CE core indicators, which then are compared with sustainability indicators. The life cycle of rare earth elements (REE) is used as a case study to validate the CE core indicators. To achieve this literature studies and comparative analysis will be performed. Existing definitions and indicators of CE were studied to compile a complete set of core indicators. These compiled CE core indicators were then compared with adapted United Nation (UN) sustainability indicators. The UN indicators were chosen after analysing several different sustainability indicator system and their compatibility with the resource perspective. The main differences between the UN indicators and CE core indicators is that the UN indicators does not include economic aspects such as market diversity and social aspects such as consumption behaviour. However, the UN indicator system includes transportation and governance that could be beneficial to include into the CE concept. The economic viability to perform the CE analysis and non-existing CE indicators for companies and countries were identified as two barriers that could hinder development and efficient use of a CE indicator system. A way to increase the economic viability is to use already generated data for the CE indicator analysis, though the economical aspect has to be studied further. The non-existing CE indicators for companies and countries are counted as a barrier due to the risk of sub-optimisation of one resource. Additionally, the CE indicator results could be misinterpreted to blame a few for the problems of the resource instead of using the results to improve all parts of the life cycle. Further research is also needed to investigate how, or even if, social aspects such as culture and society could be indicated within a CE indicator system. In conclusion, the UN indicator system could be a good baseline to develop a CE indicator system for a resource though further research is needed.

This thesis examines the way in which China's share of the rare earths global industry is constructed as a threat. The central argument of the research is that the US discourse presented a new form of danger through the lens of classical geopolitical thinking, thus, creating a new type of prospective conflict derived from resources that are perceived to be scarce and yet relatively abundant. It argues that the construction of this 'threat' that the US faces is a constant articulation of perceived vulnerabilities in shaping geopolitical identities and reinforcing ideologies through which are carried out by different actors. Rare earths are crucial for modern conditions and their applications include commercial, military and green technology but mining and production are neither economical nor environmentally friendly. The People's Republic of China is the principal exporter of these rare metals, but because of a territorial dispute in the South China Sea in 2010 it has been labelled as a monopoly power. This study seeks to examine the constructed threat that China poses to the US. China, here, is not only constructed to be a resource hungry giant but also a malicious state that would utilise its 'monopoly' status as geopolitical leverage. The thesis will employ discourse analysis and wisdoms of...

Neogene land-mammal localities are very rare in the northeastern U.S.; therefore, the late Miocene/early Pliocene Gray Fossil Site in eastern Tennessee can clarify paleoecological dynamics during a time of dramatic global change. In particular, the identification of ancient forests and past climate regimes will better our understanding of the environmental context of mammalian evolution during the late Cenozoic. Stable isotope analyses of bulk and serial samples of fossil tooth enamel from all ungulates present at the Gray site elucidate paleoecological reconstructions. The herbivorous megafauna include taxa of likely North American and Eurasian ancestry including: the tapir Tapirus polkensis, rhino Teleoceras cf. T. hicksi, camel cf. Megatylopus sp., peccary Tayassuidae, and proboscidean Gomphotheriidae. The tapir, rhino, camel, and peccary yield mean stable carbon isotope (δ13C) tooth enamel values of - 13.0‰, - 13.3‰, - 13.8‰, and - 13.1‰, respectively, suggesting forest-dwelling browsers. This range of δ13C values indicates the presence of a C3 dominated ancient local flora. Because δ13C values decline with increasing canopy density, the ancient temperate forests from the Gray site were moderately dense. The lack of significant C4 plant consumption (i.e., tooth enamel δ13C values < - 9‰) suggests the presence of forests large enough to independently support the continued browsing of sustainable populations of browsers from the Gray site. In contrast, bulk and serial δ13C values ranging from - 0.7‰ to 0.3‰ from a gomphothere tusk support a diet consisting of C4 grasses, suggesting the presence of C4 grasslands within the individuals home range. The rare earth element (REE) analyses of the gomphothere tusk and the teeth of Tapirus and Teleoceras indicates that these individuals shared similar depositional environments; thus, demonstrating the concurrent presence of C3 forests and C4 grasslands in the northeast. Stable carbon and oxygen serial sample variation of the tapir, rhino, peccary, and gomphothere is less than 1.5‰, suggesting minor differences in seasonal temperature and/or precipitation. These data support the possibility of a North American forest refugium in the southern Appalachians during a time typified by more open environments.