湖南辰溪特高有机硫煤的稀土元素特征及其成因

采用高分辨率电感耦合等离子质谱(HR-ICP-MS)技术测定辰溪晚二叠世高有机硫(7.75%)煤中的稀土元素(REEs)。辰溪煤中∑REE变化较大,从38.84 μg/g至305.85 μg/g,加权平均值为104.57 μg/g,高于世界煤均值,与中国煤相近。辰溪煤中有明显的Ce负异常(δCe=0.74~0.84)和Eu的负异常(δEu=0.55~0.69)。煤层剖面上稀土元素含量和分布模式的变化反映了成煤环境的波动,从底板到顶板陆源物质的影响减弱,而海水的影响增强。沉积环境的阶段性变化是导致剖面上下有机硫与黄铁矿硫比值相差悬殊的原因。辰溪煤中稀土元素与铁呈现了显著的正相关性(n=11,r=0.95),说明其物质来源和富集条件有一定相似性,即陆源物质和海水共同影响的结果。稀土元素的分布模式以及∑REE与灰分、Si、Al的相关性说明了其主要来源于陆源物质;辰溪煤中δCe与δEu在剖面上变化很小,说明海水对煤中的稀土元素存在重新改造的作用。     

稀土元素在植物中的分异研究进展

有关对稀土农用的理论和实践、天然和农业生态系统中稀土的地球化学行为及稀土的增产生理过程与毒理等方面已开展了大量研究,而对稀土进入植物体内的迁移过程、分布分异现象和机制缺乏必要的了解。稀土元素在植物中的分异研究有助于“示踪”稀土元素在土壤(溶液)-植物系统中的迁移路径,进而查明控制稀土元素迁移和积累的体外和体内敏感因素。本文结合近5年的研究工作,就近年来国内外有关稀土元素在植物中的分异现象、机制及其研究意义进行了综述,并展望了此方面的研究趋势,期望能为稀土以及重金属的生物有效性研究开辟一条新思路。     

In situ electrochemical characterization of natural pyrite as a galvanic catalyst using single-particle microelectrode technique in ferric sulfate solutions

Ferric reduction on the surface of pyrite, a major factor governing the overall kinetics of pyrite-assisted leaching of chalcopyrite in sulfate solutions, is investigated. In order to study the effect of pyrite on chalcopyrite leaching, four different pyrite samples were used in the leaching process. A single-particle microelectrode technique was employed to investigate the electrochemical and semiconducting properties of different pyrite samples by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy, and Mott–Schottky methods in a solution containing 0.5 mol/L sulfuric acid, 0.005 mol/L ferric sulfate, and 0.005 mol/L ferrous sulfate. During leaching, differences were observed in the behavior of different pyrite samples. CV showed a difference in the magnitude of the ferric reduction reaction peaks. An equivalent analog circuit was used to model the impedance spectra, which led to the conclusion that pyrite samples with lower charge transfer resistance are better catalysts for ferric reduction. Mott–Schottky analysis was used to quantify variations in some semiconductive and electrical properties of pyrite samples from different geographical locations.     

Speciation of Rare Earth Elements in Soil by HPLC-ICP-MS

Elemental speciation is one of the growing features of analytical chemistry of recent two decades. It is now widely recognized that the determination of total trace element contents is no longer sufficient for evaluating their pathways,environmental and biological effects, which mainly depend on their specific chemical forms existing in the samples. On the other hand, rare-earth elements (REEs), which have their unique properties, have recently been used in many fields of industry, and agriculture especially in China for increasing the crop's production. Up to now, the amount of REEs used in agriculture is more than 1000 tons per year in China.¹Such a great amount of "foreign" REEs is annually applied to the environments, what is the effect of the "foreign" REEs to the environments except the increase production brought? Moreover, how is the biological effect to living things including human beings after eating the food? To answer such questions, the speciation of REEs has a special significance.     

开滦煤洗选过程中稀土元素的迁移和分配特征

以河北开滦矿区晚古生代煤及其洗选产品为研究对象，运用电感耦合等离子体质谱（ICP-MS）和逐级化学提取的方法，对稀土元素的质量分数及其在洗选过程中的迁移和分配特征进行了研究。结果表明，开滦矿区煤中稀土元素没有明显富集；稀土元素在入洗原煤及其洗选产品中，以煤泥中质量分数最高，尾煤次之，在尾煤和煤泥中均相对富集；稀土元素在精煤中的质量分数最低；同原煤相比，中煤的稀土元素质量分数没有明显变化。原煤及其洗选的4种产品中的稀土元素分配模式基本相同，主要差别是质量分数的不同。稀土元素在洗选过程中的分配行为和赋存状态主要受控于黏土矿物，其次是有机质。     

Applicability of capillary electrophoresis to the analysis of trace rare earth elements in geological samples.

This study developed a methodology to analyze trace rare earth elements (REEs) in geological materials by capillary electrophoresis (CE). Changed from dilute HNO3 into a water medium by heating, REE ions are detectable at approximately 2 ng mL(-1). In the presence of coexisting elements from geological samples, REE separations were carried out. After sample fusion with Na2O2 and interference separation with ammonium pyrrolidinedithiocarbamate chelate, REE analytes were coprecipitated with Mg(OH)2 at pH 8.5, and then prepared into a water medium for CE determination. Using the standard addition method, this protocol was validated by analyses with better than 5% precision. This method was applied to geological materials; the REE results are in consistence with their certified values. With electrokinetic injection, internal standard (IS) selected among lanthanides is a prerequisite of high-quality REE data. An approach was proposed to derive the IS content for further correcting its contribution from unknown samples.     

稀土元素超积累植物研究进展

概述了稀土元素的环境生态学特性及其超积累植物，并对稀土元素超积累植物研究的重要科学意义进行了介绍。在此基础上，详细综述了近年来稀土元素超积累植物的研究成果，包括其种属、空间地域分布，其体内稀土元素的分布、分异特征及影响因素，其吸收富集稀土元素的生理及生化机制，并展望了稀土元素超积累植物及其修复应用研究的发展前景。     

Rotating Ring (Pt)–Disc (FeS2) Electrode Behavior in Hydrochloric Solutions

A rotating ring (Pt)–disc (FeS₂) electrode was used to investigate the surface oxidation process of pyrite in the hydrochloric solutions. It is reported for the first time that the oxidation intermediates of pyrite were formed on the disc electrode and then oxidized on the ring electrode. The results indicate that at a rotation rate of 20 Hz, when the disc electrode potential was in the region of 0.43 to 0.62 V and the ring electrode potential was at 1 V vs a standard calomel electrode (SCE), approximately 50% of the reacted pyrite was oxidized to ferric and sulfate ions and the other 50% was oxidized to sulfur and ferrous ions on the disc electrode. The latter was further oxidized to ferric ions on the ring electrode. As the disc electrode potential increased to 1.22 V vs SCE, more than 90% of the reacted pyrite was oxidized to ferric and sulfate ions on the disc electrode and less than 10% formed ferrous ions, which were further oxidized to ferric ions on the ring electrode.     

Determination of rare-earth elements by high-performance liquid chromatography/inductively-coupled plasma/atomic emission spectrometry

Liquid chromatography coupled on-line to a sequential ICP/AES system is applied for the determination of 14 rare-earth elements (REEs) in samples with widely different concentrations of REEs and matrix elements. The REEs are separated on a cation-exchanger by applying an α- hydroxyisobutyric acid gradient. The determination limits were the same as those obtained by continuous nebulization of single-element standard solutions. The chromatographic separation precludes mutual spectral interferences between the REEs. The practical value of the method developed is demonstrated by the determination of REE impurities in Specpure rare-earth oxides, by its demonstrated potential to evaluate real spectral interferences, and by the analysis of geological samples (natural phosphates) with relatively low total REE contents. The detection limits of REEs in these natural phosphates ranged between 0.005 and 0.4 μg g^?1.     

Methodologies for the analysis of rare earth elements and their relevance to reference materials

India has the third largest resources of rare earth elements (REE) in the world. These resources are essentially the monazite sand present in the beaches of south-west, south-east, and mid-eastern coasts of India. Therefore, analytical methodologies for the determination of REE in sea water and high-purity materials were developed. An overview of this work and its relevance to the preparation of standard reference materials of REE in sea water, marine sediments, and high-purity materials in the future is given.     

Methodologies for the analysis of rare earth elements and their relevance to reference materials

India has the third largest resources of rare earth elements (REE) in the world. These resources are essentially the monazite sand present in the beaches of southwest, south-east, and mid-eastern coasts of India. Therefore, analytical methodologies for the determination of REE in sea water and high-purity materials were developed. An overview of this work and its relevance to the preparation of standard reference materials of REE in sea water, marine sediments, and high-purity materials in the future is given.     

Instrumental neutron activation analysis of carbonatites from Homa Mountain, Kenya

Twenty eight (major and trace) elements including eight rare earth elements (REEs) in African carbonatite samples were determined by instrumental neutron activation analysis. The geochemical behavior of trace elements was studied in relation to the order of carbonatite intrusion from C1 to C4 through C2 and C3 at Homa Mountain, Kenya. The enrichment of Mn, Fe, Sr, Ba, Th, U and REE is found in the sixteen carbonatites examined in this study. The general increase in the concentrations of Na, Sc, Mn, Sb, Ba, Th, U and REE occurs from C1 to C4 through C2 and C2c, but C3 carbonatite shows a different pattern. The C3 carbonatite is extraordinarily enriched in Mn, Fe and Ba and is highly enriched in Cr, As, Sb and Th. The chondrite-normalized REE distribution pattern of the C3 carbonatite is not rich in the light REE. Strong fractionation between light and heavy REEs is found in the carbonatites, and moderate fractionation in the two alkalic igneous rock samples. In order to evaluate partitioning of REEs into carbonate, oxide and other mineral fractions, a selective chemical leaching technique on carbonatites was applied and is discussed in this study. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sources and availability of raw materials for fluorine chemistry

The two most important sources of fluorine are the minerals fluorite, commercially known as fluorspar, and fluorapatite, commercially known as phosphate rock.The major consumers of fluorspar are the aluminum, chemical, and steel industries. Acid-grade fluorspar, one of three commercial grades, is used primarily to make hydrogen fluoride, which is then used to produce synthetic cryolite, aluminum fluoride, fluorocarbons, and other fluorochemicals. Elemental fluorine is prepared from anhydrous hydrogen fluoride by electrolysis. Fluosilicic acid is used primarily for water fluoridation but also to make aluminum fluoride and cryolite. Reported U.S. consumption of fluorspar was 753,000 tons in 1984. U.S. demand for fluorspar was projected to increase at an average annual rate of 2.7% between 1983 and 2000.U.S. production of finished fluorspar in 1984 was 72,000 tons. Fluosilicic acid production was 61,000 tons or 107,000 tons as equivalent fluorspar. More than 85% of domestic demand was imported, primarily from Mexico and the Republic of South Africa.A U.S. Bureau of Mines investigation of major fluorspar reserves and resources in market economy countries and China found approximately 900,000 tons of demonstrated and 1,200,000 tons of identified reserves in the United States. Total world demonstrated and identified reserves were 135 million tons and 262 million tons, respectively. The potential resources of fluosilicic acid were estimated at 12 million tons of equivalent fluorspar in the United States and 360 million tons for the total world. Fluorine reserves appear adequate through the year 2000 given current projections.     

Detailed study on simultaneous separation of rare earth elements by capillary electrophoresis

Separation of all rare earth elements (REEs) by capillary zone electrophoresis was investigated in a system of alpha-hydroxyisobutyric acid (HIBA) as a main complex reagent and acetic acid (HAc) as an assistant complex reagent. In the combined system, ligand Ac- plays an important role in improving separation of Eu and Gd, and Y and Dy. The calculated ratio of Ac- to HIB- concentrations was compared and demonstrated that Eu and Gd, and Y and Dy tend to be separated at lower, and higher ratio of the two free ligands, respectively. An operational buffer system was developed for a complete separation of all REE ions.     

稀土萃取分离技术方法研究

稀土在工业诸多领域中发挥着关键作用,在增材制造材料和介电材料等高新技术领域均显示出可期的应用前景。稀土元素的分离是衔接稀土资源与高性能稀土功能材料的关键过程,所以高效提纯稀土元素变得尤为重要。本文梳理了化学沉淀法、离子交换与吸附法、萃取色层法、溶剂萃取法、液膜分离法这些经典方法和化学气相传输法、氧化还原法、萃取沉淀法、微生物法、非平衡溶剂萃取法这些新技术方法的优缺点和适用性,侧重分析了这些技术方法在节能减排方面的最新研究情况,并展望了稀土分离提纯领域的重点发展方向,以期为稀土资源的绿色高效开发利用提供依据和借鉴。     

Fl-DFO molecules@mesoporous silica materials: highly sensitive and selective nanosensor for dosing with iron ions

Highly sensitive and selective nanosensor for labile iron pool (LIP) determination, has been designed and prepared by immobilization of Fluoresceine-Desferrioxamine (Fl-DFO), a bifunctional fluoro-siderophore probe molecule with great affinity for iron ions (pKf=30.7), into highly ordered mesoporous silica structure. Different immobilization methods of Fl-DFO molecules, such as their encapsulation in surfactant micelles used as templating agents for the synthesis of mesoporous silica, direct impregnation into the mesochannels of as-synthesized mesoporous silica and their surface anchoring by covalent binding with propylamine groups implanted by post-synthesis on the internal surface of mesochannels, have been explored. Each nanohybrid has been fully characterized by small angle XRD, TEM, SEM, solid state (29)Si and (13)C MAS NMR and N(2) adsorption-desorption. The fluorescence properties of nanohybrids obtained have been correlated with the immobilization methods, generating interesting information concerning the localization of Fl-DFO molecules in the channels of mesoporous silica. The leaching of Fl-DFO molecules from mesoporous materials has been investigated. The nanosensor prepared by surface anchoring of Fl-DFO at the internal surface of mesochannels showed high performances with no leaching effect and high sensitivity in regards to its responses to ferric ions. Its fluorescence intensity decreased as soon as first Fe(III) ions are in contact with this nanosensor. A linear relationship between the fluorescence intensity and the ferric ions concentration was observed in low micromolar range. The selectivity of this nanosensor towards other metal ions has also been tested and shown its high affinity to ferric ions. This study can allow the design of a stable, portable, simple, regenerable and cost-effective nanosensor highly sensitive and selective for iron ions with detection limits in the range of cellular LIP in cells, e.g. lower micromolar range.     

Determination of nitrite with a nano-gold modified glassy carbon electrode by cyclic voltammetry

Abstract

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was employed to determine the concentration of rare earth elements (REEs) in plants and soils. Sample preparation and analytical conditions were investigated to set up a simple routine procedure for measuring rare earth elements. For prompt sample decomposition, a microwave digestion technique was successfully used with an acid mixture of HCl+HNO₃+HF. Detection limits, reproducibility, accuracy and possible interference were also studied. ICP-MS provided extremely low detection limits for REEs (0.6–6ng/l). Precision was typically better than 6% RSD (relative standard deviation) for soil and 10% for plant. The potential of the method was evaluated by analysis of standard reference materials of soils and plants. A good agreement between the experimental results and certified values was observed. The spectroscopic interference of Ba with Eu and light REEs(LREEs, La-Eu) with heavy REEs(HREEs, Gd-Lu) were eliminated by the algebra correction.

The results suggested that REEs in soil samples existed mainly as light REEs, and the same concentration distribution patterns of Oddo-Hakins law were observed, showing negative gradient from La to Lu concentrations. The REE contents in plants were very low, less than 20μg/g and varied with plant species. Apart from rape leaf(Brassica juncea), the REE distribution patterns in other plant leaves were consistent with soils, indicating that these plants generally absorbed REEs from soil without selectivity. Rape leaf showed selective absorption for LREEs, especially for La. The REE concentration distribution in parts of hot pepper(Capsicum annuum) was characteriaed by root>leaf>stem>fruit. The REEs absorbed by hot pepper concentrated mainly in roots and leaves, very little migrated into fruit. Transfer factors(TFs) of REEs in plants were very low. Although the contents of LREEs were relatively more than those of HREEs, no distinct difference of TFs between LREEs and HREEs was observed, meaning that LREEs and HREEs have the same abilities of transportation. However, for rape leaf, the TFs of LREEs were one or two orders of magnitude higher than those of HREEs.     

Determination of rare earth elements in carbonatites from the Kangankunde Mine, Malawi by instrumental neutron activation analysis

Nine rare earth elements (REEs) in African carbonatite samples were determined by instrumental neutron activation analysis (INAA). The geochemical behavior of REEs in carbonatites, especially REE pattern (chondrite-normalized), is studied in relation to carbonatite formation at the Kangankunde Mine, Malawi. REE-rich phosphate minerals, particularly monazite, and the other unusual minerals such as strontianite, are observed during the stages of carbonatite formation. Four kinds of carbonatites exhibit similar chondrite-normalized REE distribution patterns in spite of the marked difference of their REE contents. All these carbonatites are characterized by the strong fractionation between light and heavy REEs and by the very high La/Yb ratio (1000-2800).     

Separation of rare-earth elements and thorium in sorption conversion of phosphate rare-earth concentrate produced in nitric acid processing of Khibiny apatite concentrate

It is shown that REEs and thorium can be separated directly in the course of a sorption conversion of the phosphate rare-earth concentrate precipitated in nitric acid processing of the Khibiny apatite concentrate by introduction of compounds containing fluoride ions into the nitric acid solution used in the process. Under the optimal conditions, REEs are quantitatively adsorbed by the sulfo cation exchanger, whereas thorium mostly remains together with phosphorus and fluorine in the mother pulp. The influence exerted by the composition of compounds containing fluoride ions and process conditions on the separation efficiency of REEs and thorium. The suggested approach rules out formation of burial-requiring radioactive wastes with increased content of thorium.     

Effects of citrate additions to eluents in chromatographic separation of rare-earth and transplutonium elements under the ionizing radiation conditions

The influence of citrate additions to eluents based on diethylenetriaminopentaacetic acid on the separation of rare-earth elements (REEs) under irradiation were studied experimentally and theoretically. Citric acid additions to the eluent were found to increase the radiation stability of a complexone, leading to a more effective separation of elements. For citrate additions of 0.01 mol/l, the REE concentration in eluates decreased as the eluent decomposition increased. For 0.024 mol/l citrate, the dependence of REE concentration on eluent decomposition had a maximum due to the participation of citric acid in complexation with REE.