• Economic and Environmental Geology
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• v.39 no.1 s.176
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• pp.39-51
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• 2006

Rare earth elements(REEs) in transgressive shelf core sediments were analysed to identify constraints of REE distribution patterns and sediment provenances in the northern East China Sea(ECS). Sediments of Chinese and Korean rivers, such as Huanghe and Yangtz rivers, Keum and Yeongsan rivers that supply sediments to the northern ECS, were also analysed to figure out their typical REE distribution patterns. The distribution patterns of Chinese and Korean river sediments, which are normalized with upper continental crust (UCC) REE values, appear to be enriched in middle rare earth elements (MREEs) in Chinese river sediments, whereas in light rare earth elements (LREEs) in Korean river sediments. We assign the MREE-enriched convex-type distribution pattern in Chinese river sediments as 'C-type', and the LREE-enriched linearly decreasing pattern in Korean river sediments as 'D-type'. A major constraint of the REE concentration in northern ECS core sediments is interpreted to be LREE-enriched monazite $((Ce,\;La)PO_4)$ that is ubiquitous in and around the study area. Meanwhile, the distribution pattern of northern ECS sediments appears to be between the C-type and the D-type. We suggest that the nothern ECS sediments are the mixture of China and Korea riverine sediments that have been accumulated in paleo-river mouth, paleo-coast, and present-day shelf environment as well.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.3
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• pp.373-381
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• 2020

There is a need for newer feed additives due to legal prohibition on inclusion of growth promoting antibiotics in livestock diets in several countries due to antimicrobial resistance. In this context, rare earth elements (REE) have gained attention among animal nutritionists as potential growth promoters. Currently, several studies have reported better weight gain, milk production, egg laying capacity and feed conversion efficiency among different breeds of farm animals following supplementation with REE, with however largely inconsistent results. Furthermore, REE supplementation has also shown to improve ruminal fibrolytic and proteolytic activities as well as flavor of meat with negligible residues in edible tissue, however the mechanism behind this action is still unclear. According to existing research, due to their poor absorption and similarity with calcium REE might exert their action locally on gut microbial populations within the gastrointestinal tract (GIT). Moreover, REE have also shown anti-inflammatory, anti-oxidative as well as immune stimulating effects. The present review aims to broaden the knowledge about use of REE as feed additives for livestock and sum up efficacy of REE supplementation on performance and health of animals by comparing the findings. Till date, researches with REE have shown properties that make them a promising, new and safe alternative feed additive but further exploration is recommended to optimize effects and clarify discrepancy of various results before practical proposals can be drafted.

• Ocean and Polar Research
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• v.36 no.4
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• pp.383-394
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• 2014

The surface sediments from the manganese nodule exploration area of Korea in the Clarion-Clipperton fracture zone were investigated to understand the resource potential of and emplacement mechanism for rare earth elements (REEs). The sediments are categorized into three lithological units (Unit I, II and III from top to bottom), but into two groups (Unit I/II and Unit III) based on the distribution pattern of REEs. The distribution pattern of REEs in Unit I/II is similar to that of Post-Archean Australian Shale (PAAS), but shows a negative Ce anomaly and enrichment in heavy REEs (HREEs). In Unit III, the HREE enrichment and Ce anomaly is much more remarkable than Unit I/II when normalized to PAAS, which are interpreted as resulting from the absorption of REEs from seawater by Fe oxyhydroxides that were transported along the buoyant plume from remotely-located hydrothermal vents. It is supported by the PAAS-normalized REE pattern of Unit III which is similar to those of seawater and East Pacific Rise sediments. Meanwhile, the PAAS-normalized REE pattern of Unit I/II is explained by the 4:1 mixing of terrestrial eolian sediment and Unit III from each, indicating the much smaller contribution of hydrothermal origin material to Unit I/II. The studied sediments have the potentiality of a low-grade and large tonnage REE resource. However, the mining of REE-bearing sediment needs a large size extra collecting, lifting and treatment system to dress and refine low-grade sediments if the sediment is exploited with manganese nodules. It is economically infeasible to develop low-grade REE sediments at this moment in time because the exploitation of REE-bearing sediments with manganese nodules increase the mining cost.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.69-75
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• 1990

An ion-association chromatography was applied for the separation and determination of individual rare earth elements (REE) contained in mineral monazite. Prior to the determination, the group separation of REE was achieved by a cation exchange column of Dowex 5OW-X8 resin. The quantitative recovery of REE by the resin column, free from coexisting elements in monazite, was confirmed with radioactive tracers as well as with ICP-MS. Individual REE at ppm level was separated on reversed-phase column ($\mu$-Bondapak $C_{18}$) using gradient elution from 0.05 to 0.3 M $\alpha$-hydroxyisobutyric acid at pH 4.6. The individual REE was detected at 546 nm following post-column reaction with PAR (4-(2-pyridylazo)-resorcinol monosodium salt).

• Resources Recycling
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• v.27 no.6
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• pp.68-75
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• 2018

The rare earth elements (REE) contents in coal ashes generated from domestic circulating fluidized bed combustion (CFBC) were identified for evaluating the exploitation possibilities for recovering rare earth elements. Total REE contents for all of the samples in this study ranged from 82.2 ~ 311.7 ppm, much lower than the 403.5 ppm given on the average value of world coal ash. As a result of analysis using REE concentration and Outlook coefficient, six types of coal ashes falls in the unpromising area (I). These results suggest that it is difficult to recover rare earth element from coal ashes at this stage. It has been confirmed that to recover rare earth elements in coal ashes, research on the pretreatment and concentration process for critical REE is requirement.

• Journal of the Korean earth science society
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• v.42 no.4
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• pp.383-389
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• 2021

Several studies investigating the behavior and environmental distribution of rare earth elements (REEs) have been reviewed to determine the geochemical processes that may affect their concentrations and fractionation patterns in groundwater and whether these elements can be used as tracers for groundwater-rock interactions and groundwater flow paths in small catchments. Inductively coupled plasma-mass spectrometry (ICP-MS), equipped with an ultrasonic nebulizer and active-film multiplier detector, is routinely used as an analytical technique to measure REEs in groundwater, facilitating the analysis of dissolved REE geochemistry. This review focuses on the distribution of REEs in groundwater and their application as tracers for groundwater geochemistry. Our review of existing literature suggests that REEs in ice cores can be used as effective tracers for atmospheric particles, aiding the identification of source regions.

• Analytical Science and Technology
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• v.14 no.2
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• pp.103-108
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• 2001

Rare earth elements(REE) were separated by solvent extraction with tri-n-butyl phosphate(TBP) and $NaNO_3$, followed by back extraction with water. The method was applied to the determination of REE to circumvent the spectral interferences of ICP-AES analysis. The effects of the $NaNO_3$ concentration and the addition of hydrophobic solvents on the extraction efficiencies were investigated. Increases of the $NaNO_3$ concentration enhanced the extraction efficiencies of REE, and more than 95% recoveries were obtained at 5M of $NaNO_3$ concentration. On the other hand, addition of hydrophobic solvents lowered the extraction efficiencies. The method was applied to determine the REE in the monazite sample. But the precisions of the analytical results were more than 20%.

• Safety and Health at Work
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• v.10 no.4
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• pp.409-419
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• 2019

Although the rare earth elements (REEs) recycling industry is expected to increase worldwide in hightech industry, regulations for worker safety have yet to be established. This study was conducted to understand the potential hazard/risk of REE recycling and to support the establishment of regulations or standards. We review the extensive literature on the toxicology, occupational safety, and health issues, and epidemiological surveys related to the REEs, and propose suitable management measures. REE recycling has four key steps such as collection, dismantling, separation, and processing. In these processes, hazardous substances, such as REEs-containing dust, metals, and chemicals, were used or occurred, including the risk of ignition and explosion, and the workers can be easily exposed to them. In addition, skin irritation and toxicities for respiratory, nervous, and cardiovascular systems with the liver toxicity were reported; however, more supplementary data are needed, owing to incompleteness. Therefore, monitoring systems concerning health, environmental impacts, and safety need to be established, based on additional research studies. It is also necessary to develop innovative and environment-friendly recycling technologies, analytical methods, and biomarkers with government support. Through these efforts, the occupational safety and health status will be improved, along with the establishment of advanced REE recycling industry.

• Economic and Environmental Geology
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• v.55 no.3
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• pp.241-259
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• 2022

In general, the REE were produced by mining conventional deposits, such as the carbonatite or the clay-hosted REE deposits. However, because of the recent demand increase for REE in modern industries, unconventional REE deposits emerged as a necessary research topic. Among the unconventional REE recovery methods, the REE-bearing coal deposits are recently receiving attentions. R-types generally have detrital originations from the bauxite deposits, and show LREE enriched REE patterns. Tuffaceous-types are formed by syngenetic volcanic activities and following input of volcanic ash into the basin. This type shows specific occurrence of the detrital volcanic ash-driven minerals and the authigenic phosphorous minerals focused at narrow horizon between coal seams and tonstein layers. REE patterns of tuffaceous-types show flat shape in general. Hydrothermal-types can be formed by epigenetic inflow of REE originated from granitic intrusions. Occurrence of the authigenic halogen-bearing phosphorous minerals and the water-bearing minerals are the specific characteristics of this type. They generally show HREE enriched REE patterns. Each type of REE-bearing coal deposits may occur by independent genesis, but most of REE-bearing coal deposits with high REE concentrations have multiple genesis. For the case of the US, the rare earth oxides (REO) with high purity has been produced from REE-bearing coals and their byproducts in pilot plants from 2018. Their goal is to supply about 7% of national REE demand. For the coal deposits in Korea, lignite layers found in Gyungju-Yeongil coal fields shows coexistence of tuff layers and coal seams. They are also based in Tertiary basins, and low affection from compaction and coalification might resulted into high-REE tuffaceous-type coal deposits. Thus, detailed geologic researches and explorations for domestic coal deposits are required.

• Journal of the Korean Chemical Society
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• v.39 no.2
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• pp.28-81
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• 1995

Inductively coupled plasma atomic emission spectrometry was used for the determination of all 14 rare earth elements (REE) in geological materials. Samples were decomposed by using acid digestion followed by alkaline fusion. Group separation of the REE was achieved by solvent extraction with TOPO (trioctylphosphine oxide) and back extraction into HCl. The results for standard rock sample, AGV-1, showed a good agreement with those obtained by US Geological Survey as well as reported values in other articles.