Distribution of the rare earth elements in sediments of the Northwestern Iberian Continental Shelf

The temporal and spatial distribution of the REEs was determined, by INAA, in sediment cores collected at Northern Iberian shelf along the area between the Finisterra Cape and the mouth of Minho river, to contribute to the understanding of the origin and sedimentation processes of sediments deposited at the Continental Shelf. The distribution pattern of the REEs were flat and similar to the shales. A negative Eu anomaly was found for all the sections of the analyzed cores. Significant positive correlations between the REE and Zr and Hf contents suggest that zircon is responsible for hosting both light and heavy REEs.     

Distribution characteristics of rare earth elements in plants from a rare earth ore area

The contents of eight rare earth elements (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in various plant species taken from a rare earth ore area were determined by instrumental neutron activation analysis. For a given plant, the REE patterns in root, leaf and host soil are different from each other. The REE distribution characteristics in roots of various species are very similar and resemble those in the surface water. The results of this study suggest that there is no significant fractionation between the REEs during their uptake by the plant roots from soil solution. However, the variation of the relative abundance of individual REE occurs in the process of transportation and deposition of REEs in plants.     

Distribution of rare earth elements in the estuarine and coastal sediments of the Daliao River System, China

The Daliao River System (DRS) estuary in Liaodong Bay features a highly industrial, urbanized, and agricultural catchment. The objective of this study was to determine the content, behavior, and distribution of the rare earth elements (REEs) in the estuarine and coastal sediments. To this end, 35 sediment samples were collected from the estuarine and coastal area and analyzed for REEs, Fe, Al, and Mn. The mean concentrations in mg kg^?1 of the sediments were 33.4 (La), 64.1 (Ce), 7.9 (Pr), 29.0 (Nd), 5.4 (Sm), 1.2 (Eu), 4.2 (Gd), 0.78 (Tb), 4.0 (Dy), 0.84 (Ho), 2.3 (Er), 0.40 (Tm), 2.3 (Yb), and 0.37 (Lu). The REE concentrations in the sediments were significantly correlated with one another (r ²  = 0.959–0.988) and the concentrations of Fe, Al, and Mn (r ²  = 0.768–0.870). The total concentration ∑REE ranged from 73.5 to 203.5 mg kg^?1, with an average of 156.0 mg kg^?1 being observed, and generally higher in the estuarine sediments than in the coastal sediments, most likely due to the salt-induced coagulation of river colloids and subsequently their accumulation at the estuarine bottom. The ratio of light REEs (∑LREE) to heavy REEs (∑HREE) was 9.4. Chondrite-normalized REE distributions were observed to be similar for the estuarine and coastal sediments, riverine suspended particles, and watershed soils of the DRS with higher LRRE enrichment than HREE and greater Eu depletion than Ce depletion. These results demonstrate that neither geochemical processes that carry soils to estuarine sediments nor long-term industrial and agricultural activities alter the distribution or fractionation of the REEs in the study area.     

Physical fractionation of trace and rare earth elements in the sediments of Lake Nasser

The distribution of major, trace and rare earth elements in bulk, different particle sized and strongly magnetic fractions of Lake Nasser sediments has been investigated. The elements were determined using neutron activation analysis. Statistical data processing indicates good correlation between Th, La and Ce, suggesting that accessory minerals such as monazite may play a role in controlling rare earth elements (REE) in the lake sediments. The highly significant relationship between Al and light-REE accounts for the capability of clay minerals to host these elements. In addition, principle components analysis reflects that there are only four factors which could explain about 90% of the total variance in the lake sediments. The results show also that Al, Th and REE have low contents in the sediment magnetic fraction relative to the corresponding values in the bulk sediments, whereas Fe, Mn, Ti, Co, Cr, Hf, V and Zn have higher concentrations in the same fraction than the corresponding values in the bulk sediments. This may be attributed to their incorporation in Fe-Mn minerals.     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

A single structural type in the series of oxyorthosilicates of the rare earth elements

Summary We have carried out a roentgenostructural analysis of monocrystals and polycrystals of the oxyorthosilicates of rare earth elements of the third group. of rare earth elements of the third group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 925–926, May, 1965 Original article submitted August 22, 1964     

Th,U and trace elements determination in Egyiptian Lake sediments by INAA and laser fluorimetry

A study was undertaken to determine element concentrations in Aswan High Dam Lake sediments. Sediment samples were collected from 40 to 500 km upstream of the dam to follow the sedimentation process and the distribution of Th, U and the trace elements in the lake. INAA was applied for the determination of Sm, Ce, Lu, Th, Cr, Yb, Au, Hf, Ba, Nd, Cs, Tb, Sc, Rb, Fe, Zn, Co, Eu, and Sb, while Laser Fluorimetry was applied for U determination. The accuracy and the reproducibility of the techniques were tested with IAEA standard materials (SL, Soil-7). The U values ranged from 4 ppm to 18 ppm, Th values were between 2 and 10 ppm, and showed a very good correlation with the rare earth elements and Fe. The distribution of most of the elements in the lake follows the same trend as the distribution of the clays in the sediments. Ba showed a negative correlation with most of the elements under investigation.Paper presented at the 3th International Conf. on Nuclear and Radiochemistry (NRC-3), Vienna, 1992.     

Spectrophotometric determination of rare earth elements and thorium with arsenazo

The simultaneous spectrophotometric determination of rare earth elements (lanthanum and gadolinium) and thorium with arsenuzo is described. In 0.05 N nitric acid, thorium alone forms a colored complex with the reagent; at PH 7.2 both thorium and the rare carths form colored complexes. Satisfactory results were obtained with weight ratios of Th/rare earths ranging from 0.2 to 10.     

Sorption in the chemistry of rare earth elements

Sorption methods for the concentration and separation of rare earth elements are reviewed. Sorbents based on organic polymers, specifically strongly and weakly acidic cation exchangers, anion exchangers, and complexing sorbents, are successively considered. Data on the use of inorganic sorbents and solid phase extractants in the rare earth chemistry are also given. Considerable attention is paid to hybrid organomineral materials constituting a promising class of sorbents. Advantages and disadvantages of using biosorbents, molecularly imprinted sorbents, and nanosorbents for the concentration and separation of rare earths are discussed.     

Double molybdates of rare earth elements and zirconium

The results of the study of Ln₂(MoO₄)3—Zr(MoO₄)₂ molybdate systems, which made it possible to obtain new double molybdates, are summarized. The specific features of phase formation in double salt systems were determined and the formation of phases with the compositions given by three formulas Ln₂Zr₃(MoO₄)₉ (Ln = La—Tb), Ln₂Zr₂(MoO₄)₇ (Ln = Sm—Y), and Ln₂Zr(MoO₄)₅ (Ln = Tb—Lu) was established. Phase diagrams of the systems were constructed and the interrelation between the composition and the structure of the obtained phases was determined; in addition, crystallographic, thermal, and dielectric characteristics of the obtained compounds were studied.     

Removal of rare earth elements from a U/RE ingot via a reaction with UCl3

Journal of Radioanalytical and Nuclear Chemistry - A chemical equilibrium experiment was conducted to remove rare earth (RE) elements from a U/RE ingot using UCl3 as an oxidant. Upon analysis, the...     

Concentrations of rare earth elements in sediments,mussels and fish from a Danish marine environment,Lillebaelt

Results for the content of the rare earth elements (REE), La, Ce, Nd, Sm, Eu, Tb, Yb and Lu in sediments, mussels and fish are presented for an area polluted by REE. The REE are emitted with the process waste water stream from a fertilizer production plant. The method of analysis has been INAA. An attempt to combine the INAA with a simple destruction/preconcentration method is described.     

Liquid extraction of some rare earth elements with aminomethylphosphine oxides

Methods were developed of the solvent extraction from aqueous solutions of hydrochloric, nitric, and perchloric acids of the triply charged ions of rare earth elements including samarium, lutetium, dysprosium, neodymium, and ytterbium, using as reagents the lipophilic aminomethylphosphine oxides containing two or four dialkylphosphinyl groups, and toluene, chloroform, and methylene chloride as the organic media. The study of the effect of concentration of mineral acids on the degree of metal extraction showed that the highest extraction efficiency of lanthanides is achieved with bis(dihexylphosphinylmethyl)octylamine (I) from perchloric media: extraction degree 80%, whereas extraction from the solutions in two other acids did not exceed 30%. It was shown that the highest selectivity was reached at the extraction of scandium in all the extraction systems. A possible mechanism of extraction is discussed.     

The chemiluminescence of rare earth elements in sulfuric acid

It has been found that solutions of oxides of the rare earth elements (REE) in sulfuric acid exhibit chemiluminescence in the visible and ultraviolet ranges on interaction with the products of the electrolysis of H₂SO₄. Analysis of the luminescence fading curve shows that the process leading to deexcitation obeys a bimolecular law and its linear anamorphosis can be represented on coordinates I^–1/2 and t. The problem of the possible mechanism of the process involving the participation of S*O_4– ion-radicals is examined. A comparison is made with the known luminescence of the REEs, and possible explanations are put forward for the chemiluminescence of those REEs which are generally assumed to exhibit no luminescence.     

Behaviour of transplutonium and rare earth elements on TVEX

Behaviour of transplutonium and rare-earth elements on TVEX, containing TBP, HDEHP, mixture of TBPHDEHP (11), PAPNA and TOA has been studied. The analytical possibility of isolation and separation of tetravalent Pu and Bk from trivalent actinides and lanthanides from strong nitric acid solutions (1.0–12.0) on TVEX with TBP, POR, HDEHP and TOA has been demonstrated. The separation of trivalent Bk, Cf and Eu from Am and Cm is real on TVEX, containing HDEHP and mixture of TBPHDEHP.     

Determination of rare earth elements in mineral raw materials and rare earth industry products by neutron activation analysis

To determine REE in mineral raw materials, high purity RE metals and their compounds, neutron activation analysis with extraction chromatographic REE separation has been developed. Combination of the developed RE extraction and separation procedures with subsequent -spectrometric analysis of the RE radionuclides allows to determine their content with the lower detection limit –10^–5–10^–8%. The relative standard deviation is 0.2–0.3.     

Determination of rare earth elements in soils and sediments by inductively coupled plasma atomic emission spectrometry after cation-exchange separation

The influence of matrix elements such as Ba, Ca, Fe, K, Na and Ti, on the inductively coupled plasma atomic emission spectrometry determination of the rare earth elements in soils and sediments is investigated and analytical lines with minimal interferences are chosen. The analysis of certified reference materials by two calibration methods (pure rare earth solutions and IAEA-Soil 5) and after cation-exchange proved that calibrations with IAEA-Soil 5 increase the number of accurately determined rare earth elements (REE), permitting the instrumental determination of Ce, Eu, La, Nd, Tb, Yb and Y in soils and some sediments. The cation-exchange procedure permits the determination of 12 REE with very good accuracy (below 10%) and detection limits varying between 0.05 (Eu, Tb, Yb) and 0.5 (Er) mg kg(-1).     

Multiphonon decay of excited states of rare earth ions in crystals

Although the relaxation of excited electronic states through radiationless multiphonon processes has been well established by experiment, there are several serious problems concerning the current theoretical model in which the electron-phonon interaction is treated as a small perturbation, and the multiphonon transitions are attributed to high order expansion terms of perturbation theory. Here, we approach the problem in the framework of the adiabatic approximation. The rate of the multiphonon process is expressed in the form of the linear response time correlation function which is then evaluated by means of the saddle point approximation. The resulting expression predicts an approximately exponential dependence of the rate on the transition gap and a temperature dependence that agrees quantitatively with experiment.     

Neutron activation analysis of rare earth elements in deep sea sediments from the Pacific Ocean and the Japan Sea

Seven REEs in the deep sea sediments from various regions /19 sites/ of the Pacific Ocean and the Japan Sea were determined with INAA. Regional variations of La/Yb ratio and Ce anomaly may reflect the relative contribution of the source materials in the formation of the deep sea sediments.