Important Rare Earth Research Articles

Extraction of Scandium from Red Mud Using ELM with P204 as Carrier

Scandium is an important rare earth element. Stacking of red mud has caused serious environmental and social issues. Red mud is rich in scandium. In this paper, recovery of scandium from red mud by emulsion liquid membrane (ELM) was studied. Composition of ELM is P204-Span80-sulfonated kerosene-HCl. Effects of mobile carrier and surfactant concentration, Roi, Rwe, internal and external aqueous phase acidity on the extracting rate of Sc3+ were studied. Results show that it is feasible for P204-Span80-Sulfonated Kerosene-HCl ELM System extracting Sc3+ from red mud leaching solution. The optimum condition is P204=12%, Span80=3%, Roi= 2:3, Rwe=6, the internal aqueous c(HCl)= 4mol/L, the external aqueous phase pH=2, the time of making emulsion is 20 minutes, extracting time is 15 minutes. The extracting rate of Sc3+ can reach to 99.6% under optimal condition. The extracting rate of other impurities is lower than 5%.

Optical Properties of CeO2 Doped SiO2-Na2O-CaO-P2O5 Glasses

Cerium oxide is one of the most important rare earth elements that is introduced into glass compositions due to its great effects on the optical properties. CeO2 was introduced in Hench’s patented SiO2-Na2O-CaO-P2O5 glasses with different concentrations in order to study its effect on the optical behavior of this glass including optical band gap, transmittance, reflectance and refractive index and to give a complete view for the optical properties on cerium oxide-doped silicate glasses.

Jasmonic Acid (JA) Acts as a Signal Molecule in LaCl3-Induced Baicalin Synthesis in Scutellaria baicalensis Seedlings

Rare earth elements (REEs) have been widely used to increase accumulation of biomass and secondary metabolites in medicinal plants in China. However, very few studies have investigated how REEs mediate secondary metabolism synthesis in medicinal plants. Lanthanum (La), an important REE, is known to improve the accumulation of secondary metabolites in medicinal plants and is widely distributed in China. However, few studies have evaluated the signal transduction leading to La-induced secondary metabolism in medicinal plants. In this study, LaCl3 treatment-induced multiple responses in Scutellaria baicalensis seedlings, including the rapid generation of jasmonic acid (JA), sequentially followed by the enhancement of baicalin production. Direct application of JA also promoted the synthesis of baicalin in the absence of LaCl3. LaCl3-induced baicalin synthesis was blocked by two different JA synthesis inhibitors. Our results showed that JA acts as a signal component within the signaling system leading to La-induced baicalin synthesis in S. baicalensis seedlings.

Interaction between La(III) and proteins on the plasma membrane of horseradish

Lanthanum (La) is an important rare earth element in the ecological environment of plant. The proteins on the plasma membrane control the transport of molecules into and out of cell. It is very important to investigate the effect of La(III) on the proteins on the plasma membrane in the plant cell. In the present work, the interaction between La(III) and proteins on the plasma membrane of horseradish was investigated using optimization of the fluorescence microscopy and fluorescence spectroscopy. It is found that the fluorescence of the complex system of protoplasts and 1-aniline Kenai-8-sulfonic acid in horseradish treated with the low concentration of La(III) is increased compared with that of the control horseradish. The opposite effect is observed in horseradish treated with the high concentration of La(III). These results indicated that the low concentration of La(III) can interact with the proteins on the plasma membrane of horseradish, causing the improvement in the structure of proteins on the plasma membrane. The high concentration of La(III) can also interact with the proteins on the plasma membrane of horseradish, leading to the destruction of the structure of proteins on the plasma membrane. We demonstrate that the proteins on the plasma membrane are the targets of La(III) action on plant cell.

REE and actinide microdistribution in Sahara 97072 and ALHA77295 EH3 chondrites: A combined cosmochemical and petrologic investigation

We report the results of rare earth elements (REEs) and U–Th inventory of individual minerals (oldhamite, enstatite and niningerite) in two of the most unequilibrated and primitive EH3 known so far, ALHA77295 and Sahara 97072. Under the highly reducing condition that prevailed during the formation of enstatite chondrites, REEs are mainly chalcophile and concentrated in oldhamite. The study is guided by detailed petrographic investigations of the individual minerals in chondrules, complex sulfide-metal clasts and enstatite-dominated matrices. We developed two textural parameters in order to resolve the evolution of oldhamite condensates and their residence in the solar gas prior to their accretion in the individual objects or in matrices and relate these textural features to the measured REE patterns of the individual oldhamite crystals. These textural parameters are the crystal habit of oldhamite grains (idiomorphic or anhedral) and their host assemblages. REE concentrations were measured by SIMS and LA-ICPMS. Oldhamite grains display REE enrichments (10–100 × CI). Four types of REE patterns are encountered in oldhamite in ALHA77295. In general the REE distributions cannot be assigned to a specific oldhamite-bearing assemblage. The most represented REE pattern is characterized by both slight to large positive Eu and Yb anomalies and is enriched in light REEs relative to heavy REEs. This pattern is present in 97% of oldhamite in Sahara 97072, suggesting a different source region in the reduced part of the nebula or different parental EH asteroids for the two EH3 chondrites. Different parental asteroids are also supported by MgS–FeS zoning profiles in niningerite grains adjacent to troilite revealing both normal and reverse zoning trends and different MnS contents. The observed homogeneity of REE distribution in oldhamite grains in Sahara 97072 is not related to the mild metamorphic event identified in this meteorite that caused breakdown of the major K- and Rb-bearing sulfide (djerfisherite). REE concentrations in enstatite range between 0.2 and 8 × CI. Hence, enstatite is an important REE host next to oldhamite. Most patterns are characterized by negative Eu and Yb anomalies. Niningerites are negligible contributors to bulk EH3 REE inventory. Average positive Eu and Yb anomalies observed in most oldhamite are complimentary to the negative ones in enstatite thus explaining the flat patterns of the bulk meteorites. The condensation calculations based on cosmic abundances predict that the first oldhamite condensates should have flat REE patterns with Eu and Yb depletions since Eu and Yb condense at lower temperature than other REE. However, this pattern is seen in enstatite. Our findings are at odds with the predicted negative Eu and Yb anomalies in oldhamite earliest condensates from a closed system in a reduced solar source. Our petrographic, mineral chemistry and REE abundances of oldhamite, enstatite and niningerite discards an origin of oldhamite by impact melting ( Rubin et al., 2009). Our results do not support in first order the scenario of the incorporation of REE in the Earth’s core to explain 142Nd excess in terrestrial samples relative to chondrites because oldhamite is the major REE carrier phase and has super-chondritic Sm/Nd ratios.

Cerium elicitor-induced phosphatidic acid triggers apoptotic signaling development in Taxus cuspidata cell suspension cultures

Degradation of membrane phospholipids is associated with apoptotic responses, but the signaling development of this degradation is not well understood. Cerium (Ce 4+), an important rare earth element, induces cellular apoptosis and taxol biosynthesis in Taxus cuspidata suspension cultures. Here, using mass spectrometry and biochemical technique, we demonstrated that the phospholipase D (PLD) was rapidly activated by Ce 4+ and hydrolyzed structural phospholipids to generate lipid signal molecule, phosphatidic acid (PA). 1-Butanol, an antagonist of PLD-dependent PA production, blocked the biphasic burst of superoxide anions (O 2 −) and thus mitigated cellular apoptosis. The time-course analysis of PA accumulation and ERK-like mitogen-activated protein kinase (MAPK) regulation indicated PA generation preceded MAPK activation, suggesting that the rapid accumulation of PA might be required for the initial MAPK activity. After 2 h of Ce 4+ elicitation, however, PA-induced O 2 − burst, forming a negative regulation to MAPK activity, which in turn led to apoptotic signaling development.

Residence and fractionation of rare earth elements during kaolinization of alkaline peraluminous granites in NW Spain

AbstractA geochemical and mineralogical study has allowed us to address the factors controlling distribution pattern, residence and behaviour of rare earth elements (REE) during kaolinization of Variscan granitoids in NW Spain. Mineral composition of the deeply weathered samples is dominated by kaolinite, with minor amounts of quartz, muscovite-illite, alkaline feldspar and traces of resistant minerals (rutile, ilmenite, zircon and monazite). Variable amounts of Si, Na, Ca, K, Rb, Cs, Ba, U and P were lost from the weathering profile, as a result of feldspars, mica and apatite breakdown, whereas Al, Fe, Ti, Zr, Th, Hf and REE were concentrated in the residual kaolin. Chondrite-normalized REE patterns of the kaolins show an overall enrichment of light REE (LaN/SmN = 1.22–2.53), heavy REE depletion (GdN/YbN = 2.42–15.10) and a strong negative Eu anomaly (Eu/Eu* = 0.11–0.25), probably inherited from the parent granite. Nevertheless, the normalization to the parent granite reveals some REE fractionation and increasing positive Eu anomalies with advancing weathering, in response to the breakdown of feldspars. Different grain-size fractions show similar REE distribution patterns, but differ in concentration levels. Although the fine fractions are the most important REE reservoir, there is no positive correlation with clay mineralogy. The correlative behaviour among P2O5, Th and REE in the <2 mm fraction suggests that monazite plays a dominant role controlling the REE budget in the weathering profile.

Rare earth elements in rocks and minerals from alkaline plutons of the Kola Peninsula, NW Russia, as indicators of alkaline magma evolution

In order to elucidate evolutionary paths for the alkaline ultramafic series of the Kola province, we studied distribution of rare earth elements (REE) in rocks and constituent minerals of the rock sequence dunite, clinopyroxenite, melilitolite, meltejgite, ijolite, nepheline syenite. Abundances of REE and other trace elements were measured in olivine, melilite, clinopyroxene, nepheline, apatite, perovskite, titanite, and magnetite. Distribution of most trace elements in Kovdor-type rocks is shown to differ fundamentally from that in the Khibiny alkaline ultramafic suite and to have been controlled by perovskite crystallization. Primary olivine melanephelinitic melts of the Kovdor series are demonstrated to be characterized by early crystallization of perovskite, the most important REE mineral. Perovskite co-precipitating with olivine and clinopyroxene leads to a sharp REE depletion of the residual melt, to produce REE-depleted derivatives, ijolites and nepheline syenites. By contrast, the genesis of the Khibiny alkaline ultramafic series was complicated by mixing of minor batches of phonolitic melt with the primary olivine melanephelinitic magma, which led to changes in the crystallization order of REE-bearing titanates and Ti-silicates and to enrichment of late melt batches in the most incompatible elements. As a result, Khibiny ijolites have the highest REE abundances, which are accommodated by high-REE apatite and titanite.

REE-bearing sector-zoned lawsonite in the Sanbagawa pelitic schists of the eastern Kii Peninsula, central Japan

Rare-earth elements (REE)-bearing sector-zoned lawsonite was found in Sanbagawa pelitic schists in the Ise area of the eastern Kii Peninsula, central Japan. The pelitic schists consist mainly of lawsonite, chlorite, phengite, titanite, albite, quartz, calcite and weakly-ordered graphite. Metamorphic conditions are estimated at P = 3-8 kbar and T 2 O 3 up to 0.55, Ce 2 O 3 up to 1.18, and Nd 2 O 3 up to 0.58 wt%) and depleted in Ca than the {010} and {001} sectors. The {001} sector is more enriched in Ti and depleted in Al than the {100} and {010} sectors. Compositional variations in lawsonite grains suggest (super [6]) REE (super [4]) AlCa (sub -1) Si (sub -1) and (super [6]) Ti (super [4]) Al(Al, Fe (super 3+) ) (sub -1) Si (sub -1) substitutions. Lawsonite can preferentially concentrate REE, and constitutes a most important REE reservoir at high P-T metamorphic conditions, at which epidote group minerals are unstable.

Determination of rare earth elements and yttrium in rocks by inductively coupled plasma atomic emission spectrometry after solvent extraction with a mixture of 2-ethylhexyl dihydrogenphosphate and bis(2-ethylhexyl) hydrogenphosphate

The importance of rare earth elements in petrogenetic studies is well known. The inductively coupled plasma atomic emission spectrometry (ICP-AES) technique is mostly used for the determination of rare earth elements after its separation by the ion exchange method. An alternative, rapid, solvent extraction method involving a mixture of (2-ethylhexyl) dihydrogenphosphate and bis(2-ethylhexyl) hydrogenphosphate in kerosene suitable for the separation and preconcentration of REE in silicate rock is described. Major elements, such as Mg, Ca, Mn, Na and K, are not extracted appreciably from dilute hydrochloric acid solution. The extraction of the major fraction (>95%) of iron is prevented by its reduction with ascorbic acid. Titanium, Th, U and Zr are also extracted quantitatively and Al is extracted partially (∼6%). The REE are selectively stripped from the organic phase after the addition of tri-n-butyl phosphate with 4.5 mol dm –3 hydrochloric acid. Major fractions of co-extracted interfering elements (residual Fe, Th, U, Zr and Ti) remain in the organic phase. The aluminium is also stripped along with the REE; however, aluminium does not cause any interference in the determination of REE by ICP-AES. The method is applied for the preconcentration of REE in silicate rocks and its validity is checked by analyzing some Standard Reference Materials. The results are in good agreement with the recommended value. The method is simple, rapid, and suitable for the determination of REE in a silicate rock sample.

Rare earth element mobility in the oceanic lower sheeted dyke complex: evidence from geochemical data and leaching experiments

Hydrothermally altered rocks from the base metal depleted reaction zone in the lower sheeted dyke complex (ODP Hole 504B) show significant losses of rare earth elements (REE) in extensively altered domains (alteration patches). While very similar in major element composition and alteration mineralogy, the alteration patches have up to 50% lower REE concentrations than the surrounding weakly altered diabases. In order to test if there is a dependence of REE mobility on the alteration history, we carried out leaching experiments on a weakly altered diabase and an adjacent alteration patch. The leaching experiments are used as a probe to identify the hosting phases of major and trace elements before and after alteration; they are not designed to simulate natural alteration processes. Major element compositions of the leaching solutions show that small amounts (9 to 14%) of the rocks and similar proportions of plagioclase, amphibole, and chlorite were dissolved from both rock types. In contrast to the major elements, up to 100% of the REE could be leached from the strongly recrystallised alteration patch after 20 h. All leaching solutions were light REE-enriched and had negative Eu anomalies compared to the host rock. Geochemical modelling suggests that mainly interstitial material (formerly late-stage magmatic liquids) and probably some apatite are the main REE sources in the rocks affected during experimental leaching. Dissolution of plagioclase, amphibole, clinopyroxene, and chlorite cannot explain the REE compositions of the leachates. The higher REE leachability of the heavily altered rock suggests that the extensive hydrothermal alteration resulted in a complete redistribution of the REE from lattices of the magmatic minerals to the grain boundaries of secondary minerals. This can explain the marked increase in REE accessibility during ongoing alteration, which finally led to REE depletions in the highly altered rock. We propose that late-stage interstitial material provides the most important REE source of rocks in the oceanic crust. This interpretation is in contrast to a model by Klinkhammer et al. [Klinkhammer, G.P., Elderfield, H., Edmond, J.M., Mitra, A., 1994. Geochemical implications of rare-earth element patterns in hydrothermal fluids from mid-ocean ridges. Geochim. Cosmochim. Acta, Vol. 58, pp. 5105–5113.] who suggested that the similarity in the REE patterns of plagioclase and that of hydrothermal vent fluids is a result of chemical exchange between plagioclase and hot fluids in the ocean crust. Our leaching results indicate that, although dramatic dissolution of plagioclase occurred, it did not control the REE patterns of the leachates. Moreover, REE patterns inferred for fluids that mobilised REE from the highly altered rock are different from those of vent fluids. We, therefore, propose that the characteristic REE pattern of vent fluids may result from differences in aqueous chloride complex stabilities, sorption-controlled REE fractionation during fluid migration and mineral precipitation in the discharge zone.

Interoceanic variation in the rare earth, major, and trace element depositional chemistry of chert: Perspectives gained from the DSDP and ODP record

Rare earth element (REE), major, and trace element abundances and relative fractionations in forty nodular cherts sampled by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) indicate that the REE composition of chert records the interplay between terrigenous sources and scavenging from the local seawater. Major and (non-REE) trace element ratios indicate that the aluminosilicate fraction within the chert is similar to NASC (North American Shale Composite), with average Pacific chert including ~7% NASC-like particles, Indian chert ~ 11% NASC, Atlantic chert ~ 17% NASC, and southern high latitude (SHL) chert 53% NASC. Using La as a proxy for ∑REE, approximations of La ex (the amount of La in excess of that supplied by the detrital aluminosilicate fraction) indicate that Pacific chert contains the greatest La ex (85% of La total) and SHL chert the least (38% of La total). As shown by interelement associations, this La ex is most likely an adsorbed component onto aluminosilicate and phosphatic phases. Accordingly, chert from the large Pacific Ocean, where deposition occurs relatively removed from significant terrigenous input, records a depositional REE signal dominated by adsorption of dissolved REEs from seawater. Pacific chert Ce Ce * ⪡ 1 and La n Yb n ~ 0.8–1 , resulting from adsorption of local Ce-depleted seawater and preferential adsorption of LREEs from seawater (e.g., La n Yb n ~ 0.4 ), which increases the La n Yb n ratio recorded in chert. Chert from the Atlantic basin, a moderately sized ocean basin lined by passive margins and with more terrigenous input than the Pacific, records a mix of adsorptive and terrigenous REE signals, with moderately negative Ce anomalies and La n Yb n ratios intermediate to those of the Pacific and those of terrigenous input. Chert from the SHL region is dominated by the large terrigenous input on the Antarctic passive margin, with inherited Ce Ce * ~1 and inherited La n Yb n values of ~1.2–1.4. Ce Ce * does not vary with age, either throughout the entire data base or within a particular basin. Overall, Ce Ce * does not correlate with P 2O 5 concentrations, even though phosphatic phases may be an important REE carrier. This and previous studies of the large-scale controlling parameters of sedimentary REEs across ocean basins collectively indicate that REE indices of depositional regime (e.g., Ce Ce * , La n Yb n , La ex) are reproducible in a variety of sediment and rock lithologies, ages, and ocean basins, and present a coherent tool for paleoceanographic and tectonic basin reconstructions.

Characterization of selected nuclear fuel cycle materials by column extraction chromatography and ICP-AES

Current research efforts at the Argonne National Laboratory on nuclear reactor fuel developments require analytical support for the characterization of uranium metal and uranium-bearing alloys and salts. Attempts to determine trace elements at the μg −1 level in these matrices directly by inductively coupled plasma-atomic emission spectrometry (ICP-AES) proved unsuccessful. Even at moderate uranium concentrations (500 μg ml −1), severe spectral interferences for a large number of elements were observed. In particular, the spectral region of 300–400 nm contained numerous uranium lines that interfered with those of important rare earth elements. As a consequence, methods were developed that allowed the quantitative separation of 35 impurities from uranium prior to ICP-AES analysis. Column extraction chromatography was used with neutral organophosphorus compounds as extractants. Columns were prepared from tri(2-ethylhexyl)phosphate (TEHP) or di-n-hexyl-N,N-diethylcarbamoylmethylenephosphonate (DHDECMP) coated trifluorochloroethylene polymer (Plaskon). Uranium was adsorbed by the organic phase and the impurities were eluted by nitric acid. After evaporation and volume adjustment, the trace metals were determined by ICP-AES. Except for Sc and Zr, recoveries obtained using this technique were 86–107%.

Chemical changes during dyke metamorphism in high-grade basement terrains

Trace element geochemistry is an important tool in deciphering the petrogenesis of igneous, and particularly basaltic, igneous rocks, and in assigning a possible tectonic setting to these rocks1,2. Studies of the trace element geochemistry of metamorphosed igneous rocks often implicitly assume element immobility during metamorphism even though recent studies3–7 have demonstrated the sometimes quite extreme mobility of certain trace elements, and especially of the petrogenetically important rare-earth elements (REE), during low-grade (zeolite–greenschist facies) metamorphism. The mobility of trace elements at higher grades of metamorphism is poorly known, although there is some evidence8 for the mobility of large ion lithophile (LIL—Rb, K, Th, Ba, Sr) elements, but not the REE, during amphibolite fades metamorphism. The REE also seem to be stable through the amphibolite to granulite facies transition9,10. We have studied a suite of ultramafic to mafic dykes (the Scourie dykes) cutting regrogressed Lewisian granulites in the Assynt region, north-west Scotland11 and conclude that the mobility of trace elements is not controlled solely by the degree or grade of metamorphism, but more by the availability of a fluid phase for element transfer.