复合酸溶—ICP-MS/ICP-OES同时测定地质样品中28种元素

采用氢氟酸、硝酸、硫酸、高氯酸分解溶矿,用王水复溶后,移至聚乙烯试管中定容;提取1 m L澄清溶液,用(3+97)HNO3稀释至总稀释系数1 000倍后,在电感耦合等离子体质谱仪(ICP-MS)上测定Li、Be、Ga、Rb、Nb、Mo、Cd、Cs、Ta、W、Tl、Bi、Th、U元素,母液直接用电感耦合等离子体光谱仪(ICP-OES)测定Mg、Ca、Na、Co、Cu、Fe、La、Mn、Ni、Pb、Sr、Ti、Zn、V元素,此方法能充分溶解地质样品中的难溶元素和控制易挥发元素的损失,实验看出,岩石标准物质(GBW07106)、水系沉积物标准物质(GBW07309)和土壤标准物质(GBW07430)的测定值与标准值相吻合,检出限均符合规范要求。此方法准确度高,简单、快捷、实用能充分发挥大型仪器具有灵敏度高、检测限低、精密度好、线性范围宽及多元素同时测定等功能,具有样品前处理时间短、容易操作、成本低、准确度高、精密度好等优点,适合大批量地质样品多元素同时分析。     

Trace element geochemistry of the Obed Mountain deposit coals, Alberta, Canada

This study reports on the elemental concentrations and vertical variation of coal seams from the Obed Mountain deposit, Alberta Foothills, Canada. Results from two sections of Seam 1 show that the major elements (i.e. Al, Fe, Mg, K, Na, Ti, and Si) have high concentrations in intervals having high ash content, with the only exception of Ca. Similarities are apparent, in both sections, in the vertical variations of Th, U, Se, and Zn; Rb, Cs, and K; Sb, Mo, and W; Mn and Sr; and Ba, Cr, Co, Hf, and Sc. These similarities are also evident among the REEs, notably between Ce and La; also between Dy, Eu, and Sm. Most elements, with the exception of Ba and Sr are slightly more concentrated in Section 2 of Seam 1, located approximately 1.5Fig. km away from Section 1. Compared to Seam 1, Seam 2 has lower mean concentrations of elements. Boron in the coal ranges from 27 to 100 ppmw, though most values are less than 50 ppmw. Boron concentrations suggest a freshwater depositional environment. The element is depleted in the sedimentary partings (12–29 ppmw only) and is enriched in the coal interval near the roof and immediately beneath the partings. This enrichment shows possible downward mobilization of boron. Vertical variations of elements are helpful in delineating the boundaries between coal and sedimentary partings in the succession. The Obed Mountain coals are “clean” by world standards and their elemental concentrations are comparable with those in coals of a lower rank from the same coal formation used for power generation in Alberta. All sedimentary partings have low concentrations of Ba, Hf, Sc, Sr, Ta, Th, U, and REEs; this, along with the absence of an Eu negative anomaly suggests a non-volcanic origin for the partings.     

Temperature dependence of oxygen diffusion into clay‐doped PS films

Fluorescence technique was employed for the measurement of the diffusion coefficient of oxygen into polystyrene (PS) latex/modified Na‐activated bentonite (MNaLB) clay composite films. Three different MNaLB content (0, 5, and 20 wt%) composite films were prepared from PS/MNaLB mixtures by annealing them at 200°C, above the glass transition temperature of PS for 10 min. To determine the diffusivity of oxygen in PS/MNaLB composite films, diffusion measurements were performed over the temperature range from 25 to 70°C. Pyrene (P) was used as the fluorescent agent. The diffusion coefficients (D) of oxygen were determined by combining the fluorescence quenching method with Fickian transport model, and were found as a function of temperature for each MNaLB content film. The results showed that D values are strongly dependent on both temperature and clay content in composite film. It was also observed that D coefficients obey Arrhenius behavior, from where diffusion activation energies were measured. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Strontium and Silicon Simultaneous Diffusion in Single-Crystal MgO

Diffusion profiles of Sr in single-crystal MgO at 1473 to 1843 K have been determined by a depth-profiling technique using secondary ion mass spectrometry. The diffusion experiments were performed using a focusing infrared furnace. The temperature dependences of lattice and dislocation diffusion are D ¹= 2.6 × 10⁻¹¹ exp(–268.2/ RT [kJ/mol])[m².s^-1], D ^d= 1.7 × 10⁴ exp(–562.3/ RT ), respectively. The present lattice diffusion coefficients are three orders of magnitude smaller than those previously reported. Si diffused with Sr in MgO over 1583 K, and the diffusion coefficients of Si were also determined. The results of Si diffusion were equivalent to those of our previous study.     

活性白土吸附FCC催化剂胶渣中稀土元素离子的研究

对催化裂化（FCC）催化剂胶渣中有用元素进行回收,不仅实现了资源的回收利用,而且也消除了对环境的污染。以天然膨润土为原料制备得到提纯土,再制备得到活性白土,以提纯土和活性白土为吸附剂吸附催化剂胶渣中的铼离子,考察了吸附条件与性能。结果表明：活性白土对胶渣中铼离子的吸附能力强于提纯土,当活性白土的用量为0.9 g、胶渣溶液中铼离子初始质量浓度为11 mg/L、溶液的pH为4.0、吸附温度为25 ℃时,活性白土对铼离子的吸附率达到93%。该研究为FCC催化剂生产过程中有用元素的回收利用提供了技术支持。     

Diffusion of Copper in Polymer During the Metallization of PET

Thin Cu metal layers were deposited on semicrystalline poly(ethylene terephthalate) PET films by thermal evaporation. RBS measurements revealed that, under our metallization conditions, the Cu layers are buried into the polymer bulk. This has also been confirmed by ToF-SIMS measurements which reveal that some PET remain at the top surface. Since the formation of a diffuse interface has important consequences on the adhesive properties, the Cu diffusion was investigated systematically by means of RBS. After metallization, the samples were annealed under vacuum for times varying between 0 and 120 hours at 80, 90, 100, 120 and 140°C, slightly above the glass transition of the PET (67°C). Since the diffusion profiles exhibit a behavior in accordance with Fick's laws, the diffusion coefficients were evaluted. The results are in agreement with a diffusion model based on the Brownian motion of particles in a viscous fluid.     

Observations on Activity and Diffusion Coefficients in Na-Montmorillonite

Double-layer theory was used to obtain the distribution of electrical potential between adjacent clay particles. From this distribution, the activity coefficients of the sodium and chloride ions in the system were calculated. The calculated values were close to the observed ones. The porosity of the clay-water system was calculated from the density and concentration of clay. The calculated value was used to calculate the geometry factor. Then this factor and the diffusion coefficient of water in bulk water were used to calculate the diffusion that water would have in the clay if the water therein had its normal viscosity. Results indicated that the water in the clay was about twice as viscous as normal water. Having the geometry factor and the viscosity of the water in the system, it was possible to compute the diffusion coefficients that Na⁺ and Cl^? would have in the absence of electrical interaction with the clay. The computed values were close to those observed. To obtain closer agreement, electrical field strengths calculated by double-layer theory were used in an empirical equation relating viscosity and field strength to obtain the distribution of viscosity relative to the particle surfaces. Also, double-layer theory was used to obtain ionic distributions with respect to these surfaces. From the resulting distributions it was possible to determine, by means of appropriate equations, the ionic diffusion coefficients that should obtain in the clay system. Diffusion coefficients determined in this manner were somewhat better than those calculated without regard for electrical effects.     

Diffusion coefficients and accessible porosity for HTO and Cl in compacted FEBEX bentonite

The transport properties of a Spanish bentonite (FEBEX bentonite) were studied. The behaviour of the conservative anionic species ³⁶Cl⁻ is compared with HTO (neutral and conservative tracer, tritiated water). Apparent and effective diffusion coefficients, as well as the accessible porosity, were determined in a wide range of clay dry densities. Effective diffusion coefficients for HTO and ³⁶Cl⁻ were measured in through-diffusion experiments. Apparent diffusion coefficients were measured for HTO with in-diffusion (ID) experiments.A very important parameter for describing the transport of radionuclides is the accessible porosity, which is often difficult to determine, especially at high clay densities, for the anions. Therefore, it is very important to use different methods to compare the results obtained in order to understand the limitations of each technique and finally provide reliable results. Furthermore, the use of different techniques and the independent determination of each transport parameter can be used to validate the results.Apparent and effective diffusion coefficients for both HTO and Cl⁻ showed an exponential decrease when the dry density increased, with the decrease being more pronounced in the case of Cl⁻. The accessible porosity for HTO is equal to the total porosity. The accessible porosity for chloride is only a small fraction of total porosity (2–3% at a dry density of 1.65 g/cm³, when the total porosity is about 40%).     

Electrochemical study of the Eu(III)/Eu(II) system in molten fluoride media

The electrochemical behaviour of the Eu(III)/Eu(II) system was examined in the molten eutectic LiF–CaF₂ on a molybdenum electrode, using cyclic voltammetry, square wave voltammetry and chronopotentiometry. It was observed that EuF₃ is partly reduced into EuF₂ at the operating temperatures (1073–1143 K). The electrochemical study allowed to calculate both the equilibrium constant and the formal standard potential of the Eu(III)/Eu(II) system. The reaction is limited by the diffusion of the species in the solution; their diffusion coefficients were calculated at different temperatures and the values obey Arrhenius’ law. The second system Eu(II)/Eu takes place out of the electrochemical window on an inert molybdenum electrode, which inhibits the extraction of Eu species from the salt on such a substrate.     

Radionuclide Extraction by 2,6‐Pyridinedicarboxylamide Derivatives and Chlorinated Cobalt Dicarbollide

Abstract

The extraction properties of diamide derivatives of dipicolinamide (2,6‐pyridinedicarboxylamide or DPA, (R′R″NCO)₂C₅NH₃) in mixtures containing chlorinated cobalt dicarbollide in the acid form (HCCD), with and without a substituted polyethylene glycol (PEG), have been investigated. Distribution ratios of Cs, Sr, U, Eu and Am have been measured for various concentrations of diamide, PEG, aqueous phase nitric acid, with various HCCD:diamide ratios, and using different organic diluents. In the absence of HCCD, the diamides show little affinity for the extraction of Am or Eu from nitric acid solutions (distributions typically <1). Addition of HCCD with the diamide extractants indicates a pronounced synergistic effect with regard to actinide and lanthanide extraction; the observed Am and Eu distribution ratios typically increase by several orders of magnitude. Cesium is also appreciably extracted by the HCCD in the presence of the various diamides. Addition of PEG (to simultaneously extract Sr) with HCCD and diamide has minimal impacts on the Eu and Am distribution ratios. The initial data indicate that alkyl substituted DPA derivatives weakly affect the extraction properties with regard to actinides and lanthanides, while aryl substituents decrease extraction ability of the mixture. The results of this preliminary work indicate that numerous HCCD‐PEG‐DPA systems are promising and effective for the simultaneous extraction Cs, Sr, Am, and Eu from acidic solutions.     

Application of taylor dispersion technique to measure mutual diffusion coefficient in hexane + bitumen system

A novel approach with fewer technical and analytic limitations in liquid solvent‐bitumen diffusion studies is used in this article. The Taylor dispersion technique was selected for its convenient short run time experiments and reliable data analysis to find mutual diffusion coefficients in a hexane + bitumen mixture. For the first time, the infinite‐dilution molecular diffusion coefficients of bitumen in hexane were measured in both the presence and relative absence of asphaltene particles in the solution at atmospheric pressure and temperatures of 303.15, 310.15, and 317.15 K. The polydisperse nature of bitumen was clearly revealed. Results were compared with common predictive tools. Also, the asphaltene surface charge in the hexane precipitating solvent was demonstrated. Through concentration dependency investigations at atmospheric pressure and 303.15 K, it was determined that the mutual diffusion coefficients monotonically decrease as the viscosity of mixture increases within the studied 0–34% volumetric concentration of bitumen. The Taylor dispersion technique shows great potential for diffusion studies of liquid solvent‐bitumen systems. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2670–2682, 2014     

Behaviour of silicon released during alteration of nuclear waste glass in compacted clay

Long term integrated in situ experiments are performed in the HADES underground research facility (Mol, Belgium) in order to study the coupled reactivity between the different components of an underground repository for vitrified high level radioactive waste (HLW): glass, compacted clay, and stainless steel containers, at 90 °C and under gamma irradiation. Studies pertaining to the behaviour of silicon, a major element released during glass alteration, are presented here. Data collected from the integrated experiment, from simplified tests, and from modelling are put together, giving complementary information. The integrated experiment is used to investigate overall reactivity, whereas diffusion experiments coupled with modelling focused on the precipitation of silica in clay media. In the integrated in situ experiment, a bentonite clay (FoCa7) mixed with 5 wt.% of powdered glass frit was put in contact with U/Th-doped SON68 reference glass specimens for 1.2 years. One of the samples was thoroughly analysed by ESEM, SEM-EDS, TEM, XRD, and FTIR. The observations showed that after combined heating and γ irradiation, the glass/clay interface is still fully reactive. At this interface, the most important process occurring is silica precipitation either as spherical flaky nodules, or in the form of coatings on the clay surface, as chalcedony and amorphous silica. In parallel, numerical modelling was used to investigate the interactions between silica and clay material in a simplified experiment using diffusion cells. A fit between calculation results and silica migration measurements in diffusion cells was performed, including sensitivity tests with regard to the diffusion coefficients and the precipitation rate of amorphous silica. A satisfactory agreement is reached with the experimental results, using a set of reasonable fitting parameters for the FoCa7 clay material. Surface area values for silica precipitation are found to be very high, i.e. 2% of the total surface area of the clayey material indicating that silica precipitation occurs on surfaces other than those of pure silica minerals.     

Determination of gas diffusion coefficients in saturated porous media: He and CH4 diffusion in Boom Clay

Boom Clay is presently studied as the reference host formation for the disposal of high-level and long-lived radioactive waste in Belgium. In a geological repository, the production of gas is unavoidable. Gas is produced by different mechanisms: anaerobic corrosion of metals in waste and packaging, radiolysis of water and organic materials in the packages and microbial degradation of various organic wastes. Corrosion and radiolysis yield mainly hydrogen while microbial degradation leads to methane and carbon dioxide. The generated gas will dissolve in the ground water. As transport in Boom Clay is dominated by diffusion, the dissolved gas is transported away from the repository by diffusion as dissolved species. If the rate of gas generation is larger than the diffusive flux into Boom Clay, the pore water within the disposal gallery will become oversaturated and a free gas phase might form. If the gas pressure keeps increasing, free gas ingress into Boom Clay will occur, most likely through creation of new pathways. In order to make a good evaluation of the balance between gas generation and gas dissipation through engineered barriers and host formation, good estimates for the gas diffusion coefficients of the gases are needed. The currently available gas diffusion parameters for hydrogen in Boom Clay suffer from a large uncertainty, and by application of conservative values for both the source term and the gas migration term the formation of a free gas phase can presently not be excluded for some waste types.In this study a versatile method was developed to determine more precisely the gas diffusion coefficient for dissolved gases in Boom Clay. For the development of the technique, He and CH₄ were used.The proposed method is based on a through diffusion methodology and allows for two dissolved gases to diffuse through a clay sample at the same time. From the evolution of the diffusant concentration in both compartments, the apparent diffusion coefficients of dissolved He and CH₄ were obtained: 12.2 × 10^− 10 and 2.42 × 10^− 10 m²/s, with uncertainties of 10%, respectively.     

Mechanisms of immobilization of nuclear waste elements by cement minerals, cement and mortar

The mechanisms of immobilization of nuclear waste elements such as Cs, Sr, Ba, U, La and Nd (the latter two simulating Am and Cm) by three cement minerals, one cement and one mortar were investigated. Cement minerals did not immobilize Cs or Sr or Ba in the absence of CO₂ but immobilized 62 to 91% of the added Cs and all of the added Sr by forming carbonates when CO₂ was bubbled through the cement mineral suspensions. The elements La, Nd and U reacted significantly with various cement minerals, cement and mortar and precipitated as hydroxides. For example, C₃S mineral immobilized 92, 73 and 99.2 of the added La, Nd and U respectively. Reaction of cement with U resulted in the formation of basic calcium uranyl silicate hydrate or uranophane under simulated repository conditions. These results suggest that cements serve as not only physical barriers but also act as chemical barriers for the migration of especially U and transuranic elements of nuclear waste.     

Vacuum Sorption Pumping Studies of Argon and Oxygen on 4A Molecular Sieves

Abstract

Cryosorption pumping is a method of evacuating enclosed volumes by adsorbing gas on a deep bed of sorbent, such as Davison 4A zeolite, at cryogenic temperatures. Modeling the dynamic behavior of these systems for air pumping requires information on two major constituents of air: oxygen and argon. Particle size variation was the major variable in determining the mechanism of the process. The model comprises a fluid-phase mass balance representing the dynamics of gas in the bed and a spherical, one-dimensional diffusion equation describing adsorption in pellets of 4A zeolite. The present model calculates effective pore diffusivity taking into account Knudsen diffusion, ordinary diffusion, and Poiseuille flow. The primary diffusional resistance appears to occur in the macropores formed by the pelletizing clay binder, rather than in the bed interstices or microporous zeolite crystals.     

Distributions of trace elements in Western Canadian coal ashes

Concentrations of 52 minor elements in coal ash were determined using spark source mass spectroscopy. Hg levels in raw coal were investigated by cold vapour atomic absorption spectrophotometry. The concentration of elements are compared to other available data and to levels in the Earth's crust. F levels in coal ash exceed 500 μ g^?1 and may be greater than 1 wt% in raw coal. Approximately half the elements (B, S, Ni, Zn, Ga, Ge, Se, Sr, Y, Mo, Sn, Sb, I, Ba, Pr, Nd, Sm, Eu, Ho, Hf, Pt, Hg, Pb, Tl, Bi, U) investigated are enriched in the coal ash with respect to the Earth's crust. The ranges in minor element concentrations in coal ash and coal from different global regions are very similar.     

Molecular diffusion coefficients of phenylmethanol, 1-phenylethanol, 2-phenylethanol, 2-phenyl-1-propanol,and 3-phenyl-1-propanol in supercritical carbon dioxide

The Taylor–Aris chromatographic technique was employed for the determination of the diffusion coefficients of phenylmethanol, 1-phenylethanol, 2-phenylethanol, 2-phenyl-1-propanol, and 3-phenyl-1-propanol at infinite dilution in supercritical carbon dioxide from 313.16 to 333.16 K and pressures between 15.0 and 35.0 MPa. Diffusivities were correlated with temperature, pressure, solvent density and solvent viscosity, and 12 predictive equations were compared with experimental data: Wilke–Chang, Lusis–Ratcliff, Tyn–Calus, Kooijman, Lai–Tan, Catchpole–King, Eaton–Akgerman, He, He–Yu, Liu–Silva–Macedo, Dariva–Coelho–Oliveira, and Rah–Kwak–Eu–Laffleur. Considerations regarding the diffusion coefficients of the isomers were also made.     

Modelling of microporous diffusion of n-paraffins in zeolite 5A

Sorptive liquid-phase diffusion of two n-paraffins, C₁₀H₂₂ and C₁₁H₂₄, dissolved in isooctane, onto micropore of 5A zeolite was studied to assess multicomponent diffusion and competitive effects. Diffusion coefficients for adsorbing components are determined from experimental batch reactor data. The experimental data indicate that diffusion through the microporous zeolite crystals is the primary diffusional resistance. A mathematical model of the rate of adsorption of a solute from a liquid by micropore adsorbent in a batch system was developed. The equation describing the mass transport by diffusion in a micropore adsorbent has been solved in order to obtain theoretical uptake curves for systems when the adsorption equilibrium isotherm is the favourable and nonlinear one. A computer simulation of the microporous diffusion is performed by use of the ISIM-Interactive Simulation Language. The effect of main term and cross-term coefficients of micropore diffusion for the system considered is investigated.     

Adsorption Kinetics and Equilibria of Strontium onto Kaolinite

Adsorption of Sr²⁺ onto kaolinite has been studied by means of a radiotracer technique using the ⁹⁰Sr isotope. Bangham’s and McKay models have been applied to kinetic results in Sr²⁺ concentrations between trace ?0.1 mol.L^?1. The magnitudes of film and intra-particle diffusion coefficients are 10?10 and 10?14 m²·s^?1, respectively. Concentration dependence of diffusion coefficients indicated that Sr²⁺ ions are adsorbed on two different adsorption sites by an exothermic and spontaneous process. The Freundlich isotherm parameters and exchange equilibrium constants derived from selectivity coefficients indicate that Sr adsorption are depressed by competing cations in the order of Na⁺< Mg²⁺< Al³⁺.     

Transport properties of natural rubber latex layered clay nanocomposites

Natural rubber latex layered clay nanocomposites were prepared with low loadings of nanoclay using conventional compounding technique. A higher loading of clay resulted in processing difficulties due to viscosity build up. X‐ray analysis showed that nanocomposites in which layered silicate layers were either delaminated or ordered as in an intercalated structure was obtained. Partially exfoliated structure was observed from TEM photographs of nanocomposites with 3 phr nanoclay. The transport properties, sorption, diffusion, and permeation coefficients were measured using the solvent toluene at 303 K. A higher decrease for the diffusion coefficient for nanocomposites directs the presence of tortuous path for the diffusing molecules. Thermodynamic parameters show a better compatibility for the silicates with rubber resulted in the formation of an elastomeric network. Gas permeability results of the nanocomposites suggest a better barrier resistancefor oxygen molecules even in lower loading of nanoclay and different gas transport models (Nielsen, Bharadwaj, Cussler) were applied to describe the behavior of these nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008