639 research outputs found
Priorities in information desire about unknown risks
No full textPriorities in information desire about unknown risks. Lion R, Meertens RM, Bot I. Universiteit Maastricht, The Netherlands. [email protected] Research on risk perception aims to explain how people perceive risks in order to better communicate about them. Most of this research has tended to view people as passive risk perceivers. However, if confronted with an unknown risk, people can also actively seek information. The main purpose of this study was to investigate what kind of risk information people desire when confronted with an unknown risk and how this desire for information relates to the main dimensions underlying risk perception. Nine focus-group interviews were conducted. The main results of the focus groups were backed up by a paper-and-pencil questionnaire that was distributed among a random sample of 500 households in the Netherlands. Overall, people desire information with which they can determine the personal relevance of the risk confronting them. This pattern is similar to appraisal steps described by health behavior models. The focus-group results provide a dynamic picture of the way risk aspects might interact to create a final risk judgmen
Comparison of the Daluxiang and Maoniuping carbonatitic REE deposits with Bayan Obo REE deposit, China
No full textAlthough carbonatites potentially contain a larger concentration of rare earth elements (REEs) than any rock type, the origin of the REE mineralization in the world's largest Bayan Obo carbonatite-related deposit is still disputed. In order to clarify the mechanism of REE mineralization, carbonatite samples from three large REE deposits in China, Daluxiang, Maoniuping and Bayan Obo were compared. The REE minerals in Daluxiang and Maoniuping carbonatites show constant light REE (LREE) enrichment (chondrite normalized (La/Nd)(N) ratios>1), whereas those in Bayan Obo H8 dolomite marbles show variable (La/Nd)(N) ratios. The REE abundances and patterns of the REE minerals in Maoniuping carbonatites are similar to those in the barite, calcite and thread vein-hosted ores. The calcites in Daluxiang and Maoniuping carbonatites are characterized by enrichments of Pb, Sr and REEs, which is consistent with an igneous origin. They have similar REE contents and patterns to the corresponding bulk rocks, suggesting that these carbonatites are calcite-rich cumulates. During crystallization and accumulation of calcites, the REEs become enriched in carbonatite-expelled fluids because of the very low partition coefficients for these elements between carbonate minerals and melt. These fluids interact with the country rocks to produce fluorite-rich REE mineralization. The fluorites in Daluxiang and Maoniuping deposits are characterized by high Sr contents and REE patterns that vary from LREE enriched to LREE depleted. The former has relatively higher Sr and lower heavy REE (HREE) concentrations than those in Maoniuping, which is consistent with the differences found in carbonatites and calcites from the two locations. In addition, the high MnO, Sr and REE contents of dolomites in REE-Nb-Fe host H8 dolomite marble in Bayan Obo support the hypothesis that the rock is of igneous origin. In situ analyses show compositional differences between coarse- and fine-grained dolomites. The latter has higher Nb and LREEs, and lower FeO and (207)Pb/(206)Pb and (208)Pb/(206) Pb ratios. Our data confirm previous interpretations of the complex, multistage nature of REE and Nb mineralization at Bayan Obo, in which the ore is produced by reaction between carbonatite-derived fluids and the ore host dolomite marbles. This hypothesis is supported by the age of adjacent carbonatite dykes, which have the same age range as ore formation. A similar REE mineralization model is proposed for the Daluxiang and Maoniuping carbonatite deposits. (C) 2008 Elsevier B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000261217200002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Geochemistry & GeophysicsMineralogySCI(E)32ARTICLE1-212-2410
Petrogenesis and mineralization of REE-rich granites in Qingxi and Guanxi, Nanling region, South China
No full textMesozoic granites in the Nanling region, South China, are important primary rocks for ion-adsorption rare earth element (REE) deposits. Moreover, metallic deposits of W, Sn, Nb and Ta also develop in these granites, most of which formed in the Late Jurassic. The Qingxi and Guanxi granites in the Nanling region contain abundant REE minerals and have zircon U-Pb ages of 223.0 +/- 0.7 Ma and 198.8 +/- 1.4 Ma, respectively. They are of metaluminous to slightly peraluminous in character having a high K talc-alkaline composition, and have high K2O + Na2O and FeOT + MgO contents and a Ga/Al ratio similar to A-type granites. These granites plot into the post-collision field, similar to the A2-type granites. The Qingxi and Guanxi granites indicate a crust dominant origin by having high levels of Rb and Th relative to Nb and Ta normalized to ocean-ridge granites. They are characterized by LREE enrichment and the majority of REE accumulating in the primary REE minerals include REE-phosphates and fluorocarbonates. The Guanxi rocks have a stronger negative Eu anomaly, but lower REE composition than the Qingxi granites, implying that the basement may have played an important role in the REE mineralization rather than fractional crystallization. This further implies that the basement in South China may have been subjected to different evolutionary geodynamics, resulting in different multi metallic mineralization of W-Sn-Nb-Ta-REE hosted by large scale Mesozoic granites. (C) 2016 Elsevier B.V. All rights reserved.Chinese National Science Foundation [41573033, 41222022]SCI(E)ARTICLE309-3258
REE recovery from end-of-life NdFeB permanent magnet scrap: A critical review
No full textNdFeB permanent magnets have different life cycles, depending on the applications: from as short as 2–3 years in consumer electronics to 20–30 years in wind turbines. The size of the magnets ranges from less than 1 g in small consumer electronics to about 1 kg in electric vehicles (EVs) and hybrid and electric vehicles (HEVs), and can be as large as 1000–2000 kg in the generators of modern wind turbines. NdFeB permanent magnets contain about 31–32 wt% of rare-earth elements (REEs). Recycling of REEs contained in this type of magnets from the End-of-Life (EOL) products will play an important and complementary role in the total supply of REEs in the future. However, collection and recovery of the magnets from small consumer electronics imposes great social and technological challenges. This paper gives an overview of the sources of NdFeB permanent magnets related to their applications, followed by a summary of the various available technologies to recover the REEs from these magnets, including physical processing and separation, direct alloy production, and metallurgical extraction and recovery. At present, no commercial operation has been identified for recycling the EOL NdFeB permanent magnets and the recovery of the associated REE content. Most of the processing methods are still at various research and development stages. It is estimated that in the coming 10–15 years, the recycled REEs from EOL permanent magnets will play a significant role in the total REE supply in the magnet sector, provided that efficient technologies will be developed and implemented in practice.(OLD) MSE-
Rare Earth Element Deposits and Occurences Within Brazil and India: Indicating and describing the main REE deposits & occurrences and their potentialities
No full textThe aim of this thesis is to describe the rare earth element (REE) occurrences, reserves and resources in Brazil and India and to investigate future potentiality of these deposits and any other potential REE resources in South America. This report is completely based on literature studies, no experiments or fieldwork were carried out. Firstly, this thesis starts off with an introduction on what the REEs are, in which form they occur and why they are essential in today’s society. Also the topic of why Brazil and India are chosen as countries for this study will be covered. Afterwards the main REE-carrying mineral deposits within Brazil (and India as well) are described. These deposits are mainly carbonatites, granitic deposits and (mostly shoreline) placer deposits. Estimated resources and reserves are given per location, along with other information of the deposit. Information like: age, REE content and grade, other valuable mineral content and the feasibility and future potentiality of the deposits. Furthermore, a link will be made between some of the described (granitic) deposits within Brazil and potentially other resources in South America. For India, the main mineral deposits are described in the same manner as for Brazil. However, for the sake of the length of this report the descriptions are limited to the currently operating Indian Rare Earths Limited (IREL) plants. For India, as well as for Brazil, more (less significant) deposits are briefly displayed in the Appendices found at the end of the report.Civil Engineering and GeosciencesGeoscience & Engineerin
Posht-e-Badam Metallogenic Block (Central Iran): A suitable zone for REE mineralization
No full textOne of the most important ores for REE mineralization are iron oxide–apatite (IOA) deposits. The Posht-e-Badam Block (PBB) is a part of the Central Iranian geostructural zone which is the host of most important Fe deposits of Iran. Exploration studies of the IOA deposits within the PBB (e.g. Esphordi, Gazestan, Zarigan, Lak-e-Siah, Sechahoun, Chahgaz, Mishdovan, Cheshmeh Firouzi and Shekarab) demonstrate that these deposits contain high contents of REE. Concentrations of ΣREE in the most important IOA deposits of the PBB include the following: the Esphordi deposit varies between 1.2 and 1.88%, the Gazestan deposit between 0.17 and 1.57%, the Zarigan deposit between 0.5 and 1.2% and the Lak-e-Siah deposit varies between 0.45 and 1.36%. Concentrations of ΣREE within the apatite crystals present within the IOA ores in the Esphordi, Lak-e-Siah and Homeijan deposits have ranges between 1.9–2.54%, 1.9–2.16% and of 2.55%, respectively. These elements are mainly concentrated in apatite crystals, but other minerals such as monazite, xenotime, bastnasite, urtite, alanite, thorite, parisite–synchysite and britholite have been recognized as hosts of REEs, as small inclusions within the apatite crystals, and in subsequent carbonate, hematite–carbonate and quartz veins and veinlets. Given the extent of this block and the presence of several IOA deposits within this block, and also the high grades of REEs within these deposits, one can reasonably state that it is obvious that there are significant resources of REEs in this part of Iran
Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform
No full textThis study reports the first well-defined and stable nanomicelles (20 - 30 nm in diameter) self-assembled from amphiphilic brush (comb-like) cyclic and tadpole-shaped copolymers composed of hydrophobic n-decyl and hydrophilic 2-(2-methoxyethoxy)ethoxy) ethyl bristle blocks based on a poly(glycidyl ether) backbone. The micelle formation behaviour and structural details were investigated by synchrotron X-ray scattering analysis in a rigorous and complementary manner. The amphiphilic brush cyclic topology facilitates more compact and stable aggregation behaviour in the micelle core and a more densely packed corona, which prevents intermicellar aggregation. The presence of a hydrophobic component with brush cyclic topology inside the core is identified as the primary micelle stabilizing factor, enabling stable core aggregation and sharper core-corona interface formation. The presence of a hydrophilic brush cyclic component in the corona is determined as the secondary micelle stabilizing factor, helping nullify the corona penetration by polymer chains from other micelles and ultimately prevent the intermicellar aggregation-mediated collapse of the micellar structure. Overall, the brush cyclic topology was confirmed to be beneficial for forming highly stable nanomicelles with an extremely narrow (pseudo-monodisperse) size distribution compared with conventional linear topology and tadpole topologies. All the results of this study provide a unique opportunity for designing advanced functional high-performance amphiphilic materials for nanomicelles that are unattainable by other conventional methods and broadening their applications in various fields, including drug delivery, biomedical imaging, foods, cosmetics, smart coatings, photonics and molecular electronics. c. The Author(s) 201711sci
Adsorption of REE(III)-humate complexes onto MnO2: Experimental evidence for cerium anomaly and lanthanide tetrad effect inhibition
Full text linkInternational audienceAdsorption experiments of rare-earths elements (REE) onto MnO2 have been conducted to evaluate the effects of REE organic complexation on both REE(III) adsorption kinetics and Ce(III) oxidation rates. Two types of aqueous solutions-NaCl and NaNO3-were tested at pH 5 and 7.5. REE(III) adsorption kinetics and Ce(III) oxidation rates is evidenced to depend strongly on REE speciation. Time-series experiments indicate that a stationary exchange equilibrium is reached within less than 10 h when dissolved REE(III) occurs as free species whereas steady state is not reached before 10 d when REE occur as REE-humate complexes. Humate complexation also results in an inhibition of positive Ce anomalies and M-type lanthanide tetrad effect development in REE patterns. Monitoring of dissolved organic carbon (DOC) concentrations showed that ratios of DOC d REE d K log K log organic ratios were close to 1.0, implying that the REE(III) and humate remained bound to each other. The lack of Ce anomaly development when REE occurred as REE-humate complexes seems to arise from the humate shielding of the MnO2 surface and Ce(IV) preferential adsorption inhibition. The suppression of the lanthanide tetrad effect suggests that REE(III)-humate complexes is bound to MnO2 by the humate side (anionic adsorption). Thus, Ce cannot be used as a reliable proxy of redox conditions, in either organic-rich waters, or precipitates formed at equilibrium with organic-rich waters. Furthermore, they explain why despite the Author to whom correspondence should be addressed ([email protected]) 2 development of strongly oxidizing conditions and the presence of MnO2 in the aquifer, no (or insignificant) negative Ce anomalies are observed in organic-rich waters
Petrological and geochemical characteristics of Zhaibei granites in Nanling region, Southeast China: Implications for REE mineralization
No full textMineralization with ion adsorption rare earth elements (REEs) in the weathering profile of granitoid rocks from Nanling region of Southeast China is an important REE resource, especially for heavy REE (HREE) and Y. However, the Jurassic granites in Zhaibei which host the ion adsorption light REE (LREE) ores are rare. It is of peraluminous and high K calc-alkaline composition, which has similar geochemical features of high K2O + Na2O and Zr + Nb + Ce + Y contents and Ga/Al ratio to A-type granite. Based on the chemical discrimination criteria of Eby [Geology 20 (1992) 641], the Zhaibei granite belongs to A1-type and has similar source to ocean island basalts. The rock is enriched in LREE and contains abundant REE minerals including LREE-phosphates and halides. Minor LREE was also determined in the feldspar and biotite, which shows negligible and negative Eu anomalies, respectively. This indicates that the Zhaibei granite was generated by extreme differentiation of basaltic parent magmas. In contrast, granites associated with ion adsorption HREE ores contain amounts of HREE minerals, and show similar geochemical characteristics with fractionated felsic granites. Note that most Jurassic granitoids in the Nanling region contain no REE minerals and cannot produce REE mineralization. They belong to unfractionated M-, I- and S-type granites. Therefore, accumulation of REE in the weathering profile is controlled by primary REE mineral compositions in the granitoids. Intense fractional crystallization plays a role on REE enrichment in the Nanling granitoid rocks. (C) 2014 Elsevier B.V. All rights reserved.GeologyMineralogyMining & Mineral ProcessingSCI(E)[email protected]; [email protected]
До інтерпретації етруського напису з Риму (REE 47/29)
No full textУ статті здійснена спроба тлумачення етруського напису, знайденого у Римі у районі церкви Сант Омобоно під час розкопок храму Фортуни і Матер Матути другої чверті VI ст. до н. е. Критичний аналіз результатів передуючих досліджень змушує відкинути інтерпретації попередників. Автор доходить висновку, що пластинка у формі лева з написом (REE 47/29) була посвятою до храму від нащадка сирійських різьбярів по слоновій кістці, що асимілювалися у Римі за правління царів етруського походження.
В статье предпринята попытка толкования этрусской надписи, обнаруженной в Риме в районе церкви Сант Омобоно при раскопках храма Фортуны и Матер Матуты второй четверти VI в. до н. э. Критический анализ результа-тов предыдущих исследований заставляет отбросить интерпретации пред-шественников. Автор приходит к выводу, что пластинка в форме льва с над-писью (REE 47/29) была посвящением в храм от потомка сирийских резчиков по слоновой кости, ассимилировавшихся в Риме при правлении царей этрусского происхождения.
It is a new attempt to interpret an Etruscan inscription, found in Rome near the Saint’Omobono Church, during excavations of the temples of Fortuna and Mater Matuta, dated back to the second quarter of the sixth century BCE. Critical analysis of the previous studies makes to reject the interpretations of forerunners. The author comes to conclusion that the plate in form of a lion with inscription (REE 47/29) was a dedication for the temple from a descendant of Syrian ivory cutters who had assimilated in Rome under the reign of kings of Etruscan origin
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