SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Rare earth element

131

Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features. Here, we estimated the resource amount in REY-rich mud with Geographical Information System software and established a mineral processing procedure to greatly enhance its economic value. The resource amount was estimated to be 1.2 Mt of rare-earth oxide for the most promising area (105 km2 × 0-10 mbsf), which accounts for 62, 47, 32, and 56 years of annual global demand for Y, Eu, Tb, and Dy, respectively. Moreover, using a hydrocyclone separator enabled us to recover selectively biogenic calcium phosphate grains, which have high REY content (up to 22,000 ppm) and constitute the coarser domain in the grain-size distribution. The enormous resource amount and the effectiveness of the mineral processing are strong indicators that this new REY resource could be exploited in the near future.

Concepts: Geographic information system, Japan, Pacific Ocean, Ocean, Rare earth element, Yttrium, Terbium, Dysprosium

30

Recycling rare earth elements (REEs) used in advanced materials such as Nd magnets is important for the efficient use of REE resources when the supply of several REEs is limited. In this work, the feasibility of using salmon milt for REE recovery and separation was examined, along with the identification of the binding site of REEs in salmon milt. Results showed that (i) salmon milt has a sufficiently high affinity to adsorb REEs and (ii) the adsorption capacity of the milt is 1.04 mEq/g, which is comparable with that of commercial cation exchange resin. Heavier REEs have higher affinity for milt. A comparison of stability constants and adsorption patterns of REEs discussed in the literature suggests that the phosphate is responsible for the adsorption of REE in milt. The results were supported by dysprosium (Dy) and lutetium (Lu) LIII-edge extended x-ray absorption fine structure (EXAFS) spectroscopy. The REE-P shell was identified for the second neighboring atom, which shows the importance of the phosphate site as REE binding sites. The comparison of REE adsorption pattern and EXAFS results between the milt system and other adsorbent systems (cellulose phosphate, Ln-resin, bacteria, and DNA-filter hybrid) revealed that the coordination number of phosphate is correlated with the slope of the REE pattern. The separation column loaded with milt was tested to separate REE for the practical use of salmon milt for the recovery and separation of REE. However, water did not flow through the column possibly because of the hydrophobicity of the milt. Thus, sequential adsorption-desorption approach using a batch-type method was applied for the separation of REE. As an example of the practical applications of REE separation, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste by a batch-type method using salmon milt.

Concepts: DNA, Adsorption, Materials science, Rare earth element, Lutetium, Lanthanide, Ytterbium, Dysprosium

28

In order to confirm the possibility that recycled fractions from the Waste Electrical and Electronic Equipment (WEEE) stream were illegally entering the European market in black polymeric food-contact articles (FCAs), bromine quantification, brominated flame retardant (BFR) identification combined with WEEE relevant elemental analysis and polymer impurity analysis were performed. From the 10 selected FCAs, seven samples contained a bromine level ranging from 57 till 5975 mg kg(-1) which is lower than expected to achieve flame retardancy. The BFRs which were present were tetrabromobisphenol A (TBBPA), decabromodiphenylether (decaBDE), decabromodiphenylethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE). Typical elements used in electronic equipment and present in WEEE were detected either at trace level or at elevated concentrations. In all cases when bromine was detected at higher concentrations, concurrently antimony was also detected which confirms the synergetic use of antimony in combination with BFRs. This study describes also the measurement of rare earth elements (REEs) where combinations of cerium, dysprosium, lanthanum, neodymium, praseodymium and yttrium which were detected in four of the seven BFR positive samples. Additionally, the polymer purity was investigated where in all cases foreign polymer fractions were detected. Despite the fact that this study was carried-out on a very small amount of samples there is a significant likelihood that WEEE has been used for the production of FCAs.

Concepts: Flame retardant, Rare earth element, Chemical elements, Yttrium, Brominated flame retardant, Cerium, Lanthanide, Monazite

28

End-of-life recycling is promoted by OECD countries as a promising strategy in the current global supply crisis surrounding rare earth elements (REEs) so that dependence on China, the dominant supplier, can be decreased. So far the feasibility and potential yield of REE recycling has not been systematically evaluated. This paper estimates the annual waste flows of neodymium and dysprosium from permanent magnets -the main deployment of these critical REEs-during the 2011 to 2030 period. The estimates focus on three key permanent magnet waste flows: wind turbines, hybrid and electric vehicles, and hard disk drives (HDDs) in personal computers (PCs). This is a good indication of the end-of-life recycling of neodymium and dysprosium maximum potential yield. Results show that for some time to come, waste flows from permanent magnets will remain small relative to the rapidly growing global REE demand. Policymakers therefore need to be aware that during the next decade recycling is unlikely to substantially contribute to global REE supply security. In the long term, waste flows will increase sharply and will meet a substantial part of the total demand for these metals. Future REE recycling efforts should, therefore, focus on the development of recycling technology and infrastructure.

Concepts: Magnetic field, Magnet, Magnetism, Computer, Recycling, Rare earth element, Neodymium, Hard disk drive

28

The heptadentate Schiff base ligand, 2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazoline (H(3)api), yields [Ln(2)api(2)] species when combined with lanthanide salts under basic conditions. A survey of the magnetic properties of this dinuclear lanthanide motif (Ln = Gd, Tb, Dy, Ho) has identified weak magnetic exchange, antiferromagnetic in nature for the isotropic gadolinium analogue, while single molecule magnetic behaviour is displayed in the case of the anisotropic dysprosium complex.

Concepts: Ammonia, Paramagnetism, Magnetism, Ferromagnetism, Rare earth element, Terbium, Lanthanide, Lanthanides

27

Single-molecule magnets are compounds that exhibit magnetic bistability caused by an energy barrier for the reversal of magnetization (relaxation). Lanthanide compounds are proving promising as single-molecule magnets: recent studies show that terbium phthalocyanine complexes possess large energy barriers, and dysprosium and terbium complexes bridged by an N2(3-) radical ligand exhibit magnetic hysteresis up to 13 K. Magnetic relaxation is typically controlled by single-ion factors rather than magnetic exchange (whether one or more 4f ions are present) and proceeds through thermal relaxation of the lowest excited states. Here we report polylanthanide alkoxide cage complexes, and their doped diamagnetic yttrium analogues, in which competing relaxation pathways are observed and relaxation through the first excited state can be quenched. This leads to energy barriers for relaxation of magnetization that exceed 800 K. We investigated the factors at the lanthanide sites that govern this behaviour.

Concepts: Magnetic field, Magnetism, Ferromagnetism, Magnetic moment, Hysteresis, Excited state, Rare earth element, Dysprosium

27

Fourteen rare earth elements were determined in mosses (Pleurozium schreberi) and soils (subhorizon-Ofh and -Ol, mixed horizon-AE and AEB) from south-central Poland. The results were normalized against North American Shale Composite (NASC) and Post-Archean Australian Shales (PAAS). The distribution of REEs in the moss-soil system differed considerably, but all the samples showed the average percent of increase of medium rare earth elements. The shale-normalized concentration ratios calculated for selected elements (LaN/YbN, GdN/YbN, LaN/SmN) were in the range of 1.22-2.43, 1.74-3.10 and 0.86-1.09. Both subhorizon-Ofh (-Ol) and horizon-AE (-AEB) showed a weak enrichment of Gd. The shale-normalized patterns of soils showed a somewhat negative Eu anomaly in the horizon-AE (-AEB), and a slightly negative Ce anomaly in the subhorizon-Ofh (-Ol). A strongly positive Eu anomaly and a somewhat negative Nd anomaly were found in the moss samples.

Concepts: Concentration, Rare earth element, Stratum, Mosses

26

A series of luminescent rare-earth ion-doped hexagonal II-type Gd oxycarbonate phosphors Gd2-xRExO2CO3 (RE= Eu3+, Yb3+, Dy3+) have been successfully synthesized by thermal decomposition of the corresponding mixed oxalates. The Yb3+ doped Gd-oxycarbonate has evidenced a high persistent luminescence in the NIR region, that is independent from the temperature and makes this materials particular attractive as optical probes for bio-imaging.

Concepts: Luminescence, Phosphorescence, Rare earth element, Europium

25

Uranyl acetate (UAc) has been generally used not only as a superb staining reagent for ultrathin sections of plastic-embedded biological materials, but also as high-contrast negative stains for biological macromolecules such as particles of protein or virus. However, the use and purchase of radioactive UAc have been restricted. In this study, we determine the performance of ytterbium triacetate, lutetium triacetate, samarium triacetate and gadolinium triacetate as new staining reagents for biological electron microscopy. We observed chemically fixed spinach (Spinacia oleracea) leaves stained with these reagents. Ultrathin sections were stained with these reagents. Some of them were counterstained with lead citrate. The transmission electron microscopy contrast of spinach organelles was evaluated in sections exposed to the conventional stain and new stains. We show acetate salts of samarium, gadolinium, ytterbium and lutetium could be excellent substitutes for UAc for thin section staining and for negative staining. In addition, each reagent showed appreciable negative-staining effects.

Concepts: Biology, Microscope, Transmission electron microscopy, Staining, Stain, Rare earth element, Lanthanide, Negative stain

24

This paper proposes a forecast of certain rare earth flows in Europe at the 2020 horizon, based on an analysis of trends influencing various actors of the rare earth industry along the value chain. While 2020 is indicated as the forecast horizon, the analysis should be considered as more representative of the next decade. The rare earths considered here are used in applications that are important for a low-carbon energy transition and/or have a significant recycling potential: NdFeB magnets (Pr, Nd, Dy), NiMH batteries (Pr, Nd) and fluorescent lamp phosphors (Eu, Tb, Y). An analysis of major trends affecting the rare earth industry in Europe along the value chain (including extraction, separation, fabrication, manufacture, use and recycling), helps to build a scenario for a material flow analysis of these rare earths in Europe. The scenario assumes in particular that during the next decade, there exists a rare earth mine in production in Europe (with Norra Kärr in Sweden as a most likely candidate) and also that recycling is in line with targets proposed in recent European legislation. Results are presented in the form of Sankey diagrams which help visualize the various flows for the three applications. For example, calculations forecast flows from extraction to separation of Pr, Nd and Dy for magnet applications in Europe, on the order of 310tons, 980tons and 80tons rare earth metal resp., while recycled flows are 35tons, 110tons and 30tons resp. Calculations illustrate how the relative contribution of recycling to supply strongly depends on the situation with respect to demand. Considering the balance between supply and demand, it is not anticipated any significant shortage of rare earth supply in Europe at the 2020 horizon, barring any new geopolitical crisis involving China. For some heavy rare earths, supply will in fact largely outweigh demand, as for example Europium due to the phasing out of fluorescent lights by LEDs.

Concepts: Fluorescent lamp, Phosphor, Rare earth element, Yttrium, Terbium, Europium, Dysprosium, Rare-earth magnet