四酸密闭消解-电感耦合等离子体质谱(ICP-MS)法测定铀矿中的铼和钪

建立一种准确测定铀矿中铼和钪含量的方法,为铀矿中伴生元素的分析与研究提供数据支持、对探勘铼钪矿实现战略资源合理利用化有着重大意义。采用氢氟酸-硝酸-盐酸-高氯酸四酸溶解样品,利用密闭聚四氟乙烯坩埚-电热板加热方式来测定铼钪,建立了电感耦合等离子体质谱(ICP-MS)法测定铀矿中铼和钪的方法,探讨了分解方法、称样量、酸用量、溶样温度及时间、基体干扰、内标选择的影响。实验结果表明：酸溶分解结果准确性高于碱溶分解,3 mL HF、4 mL HNO3、2 mL HCl和1 mL HClO4为最佳消解体系,0.05 g~0.10 g、10 mL~12 mL为最佳称样量和酸用量,闭盖160 ℃、开盖190 ℃ 18 h为最佳溶样条件,选择碰撞气流速为3.0 mL/min,稀释气流速为0.8 L/min降低基体干扰,In作为内标能够达到测试要求。该方法操作简单同时将铼钪测试,其中铼和钪的检出限分别为0.006 mg/kg和0.366 mg/kg;铼准确度在92.9%~98.4%,相对标准偏差在2.4%~5.7%,钪准确度在93.5%~98.2%,相对标准偏差在1.6%~6.2%;铼加标回收率为87.2%~93.8%,钪加标回收率为90.7%~92.3%,检出限低,精密度良好,灵敏度低满足铀矿中铼和钪的分析要求。     

Structure and Orientation of Tetracarboxylic Acids at Oil–Water Interfaces

Fouling caused by tetracarboxylic acids in transport and separation process chains involving petroemulsions occurs when the interfacial concentration of tetraacids becomes large enough for calcium ions in the water phase to “crosslink” the adsorbed tetraacid molecules and form a precipitate. At present, the structure and orientation of tetraacid molecules at oil–water interfaces, which influences the precipitation behavior, has not been studied in detail. In this work, molecular dynamics simulations of indigenous and synthetic tetracarboxylic acid compounds are presented to describe the structure and spatial orientation of tetraacid molecules at oil–water interfaces. Molecular distributions relative to the oil–water dividing surface along with the length and orientation angle distributions of the acidic arm groups are presented. The probability distributions determined here that describe the tetraacids at an oil–water interface can be employed to reconstruct the density of carboxylic acid groups at the oil–water interface. The interfacial carboxylic acid density can be employed to determine the fraction of adsorbed tetraacid molecules that are “crosslinked” with calcium ions based on the distances between carboxylic acid groups. The simulations presented also form a basis to calculate interfacial molecular areas and virial coefficients to employ in molecular mixed monolayer adsorption isotherms.     

Limitations and Applicability of the Interfacial Shear Rheology in the Study of Monolayer Films at the Air-Water Interface

This article studies the applicability of a new technique in determining the interfacial shear rheology properties of surface active compounds relevant to the petroleum industry. It presents the theory behind the determination of the rheological parameters and the results of tests performed on a set of petroleum related compounds (asphaltenes, tetra-acid model compound, fatty acid, and surfactant). It is concluded that this technique is not mature enough to determine the properties of the studied compounds.     

Model Compounds for Asphaltenes and C80 Isoprenoid Tetraacids. Part I: Synthesis and Interfacial Activities

Three model compounds for asphaltenes and two model compounds for the C₈₀ isoprenoid tetraacids (ARN) have been synthesized and their interfacial and solubility properties were investigated. All compounds exhibit high interfacial activities. The asphaltene models lowered the interfacial tension between toluene and pH 9 to around 5 mN/m at 12.5–35 μM and the tetraacid models gave a drop in the interfacial tension between chloroform and pH 9 to 13 mN/m at only 5 μM, which is consistent with previous findings for the natural occurring C₈₀ tetraacids. A sudden drop in the IFT over a very narrow concentration range was observed for two of three asphaltene models. NIR spectroscopy studies indicated an aggregation most likely a result of polar and hydrogen bond interactions. The IFT results also showed different behavior with only small changes in chemical structure. The tetraacid models have similar interfacial behavior as the C₈₀ tetraacids and will thus be suitable model compounds with their highly UV active and fluorescent properties.     

Characterization of C80 Naphthenic Acid and Its Calcium Naphthenate

A C80 naphthenic acid (tetraacid) and its calcium naphthenate have been characterized with respect to their interfacial properties at both the oil/water and the air/water interfaces as well as their thermal properties. Naphthenic acids in crude oils may give rise to different problems in oil production including naphthenate deposition and formation of stable emulsions. This may lead to severe disturbances of regularity and shut‐in in the oil production. The interfacial activity and film properties of the compounds were examined by the oscillating drop method. The calcium naphthenate film was primarily elastic and solid‐like. Measurements on the acid gave similar results, an elastic, solid‐like film was formed, but the effect was less pronounced than for the calcium naphthenate. Langmuir‐Blodgett films of the acid and its naphthenate were deposited on conducting substrates and subsequently analyzed by scanning electron microscopy, SEM. It was found that the pure acid formed crystalline structures in the interfacial film on compression. The calcium naphthenate, on the other hand, form a continuous amorphous film on the substrate.     

Synthesis and Characterization of 5,5'''',6,6''''-(2,2-Bipyridine)tetraacid

It is well known that the dianhydride based on aromatic tetraacid plays a critical role in the preparation of polyimides, polypyrrolones or their copolymers, specially all kinds of polyimides have widely gotten applications in advanced technologies1-3. Polyimide exhibits a serials of excellent performances, e.g. high strength, modulus, heat resistance, dielectric property, chemical stability as well as radioresistance2, meanwhile, polypyrrolone should be also a promising high performance mater…