冠醚分离锂同位素研究——Ⅱ.锂盐-冠醚两相交换体系的锂同位素效应

本文报道了我们用冠醚萃取分离锂同位素的研究工作的一部分,共用八种不同类型的冠醚。它们是15—冠—5及其衍生物共三种、饱和的八甲基四氧Ouaterene固状物和油状物两种及开链冠醚三种。实验测定的数据包括锂同位素交换反应速度、同位素分离因数及锂在两相中的分配比。测得各体系的锂同位素分离因数在1.012—1.030之间,其中最高分离因数是环已基—15—冠—5的体系,达到1.030±0.005。测得该体系的同位素交换反应速度是快的,锂同位素交换达到平衡的时间小于10s。本文对实验结果的分析和讨论着重于冠醚结构对同位素分离因数及锂在两相中的分配的影响,它包括冠醚空穴的大小、冠醚的类型及冠醚所带有的边环及边环上的取代基的影响。     

锂盐-冠醚络合物化学交换体系中的同位素效应

对8种锂盐-冠醚络合物的两相体系进行化学交换并确定了平衡单级分离系数。证实了同位素效应与两相化合物种的键强差有很大关系,揭示了影响分离系数的因素。找到了一种迄今尚未公开发表的4甲基-苯并-15-冠-5体系,其萃取分离锂同位素的单级分离系数达到了1.035—1.047。环己基-15-冠-5体系单级分离系数为1.035。在没有价态变化的条件下进行~6Li的浓集。所有情况,~6Li均浓集在有机相中。采用一种新的大有机阴离子——三氯乙酸根作为对离子进行萃取,代替Jepson使用过的三氟乙酸(HTFA)。研究了溶剂对分离系数的影响,采用介电常数稍高的1.2-二氯乙烷为溶剂,物化性能好、两相比重适宜,有利于同位素分离。在实验的基础上,探讨了结构与性能之间的内在联系。表明,大环效应是显著的。展示了锂盐-冠醚络合物化学交换体系萃取分离锂同位素的前景是乐观的。进一步为发现新的体系,探讨工艺应用可能性,提供依据。     

多醚液-液萃取体系中各种因素对锂的热力学同位素效应的影响

利用经验式ε_P=(a-1)/[1+0.46(1-P)],处理含多醚液-液萃取体系的数据,考察该类体系中冠醚的内结构、冠醚的侧基、冠醚浓度、有机溶剂、锂盐阴离子、锂盐浓度等因素对锂的热力学同位素效应的影响。     

冠状化合物在锂同位素分离中的应用

锂有两种稳定的同位素且在核能工业中都有重要的应用,工业上分离锂同位素的方法为锂汞齐法,但该法需使用大量有毒的汞,对人类健康和环境卫生带来了严重问题,因此寻找一种绿色有效的替代方法势在必行。自冠醚和穴醚合成后,在锂同位素分离上的优良特性使其成为了国内外研究热点,本工作将近40年来冠状化合物在锂同位素分离中的研究成果进行了系统的归类和总结,为该领域的进一步研究提供参考。     

4-叔丁基苯并-15-冠-5液-液萃取法分离锂同位素

本文测定了以4-叔丁基苯并-15-冠-5作络合剂的H_2O/C_6H_51双液萃取体系分离锂同位素的若干参数。发现大环多醚双液萃取锂盐体系的(α—1)对(1—p)有线性关系,α为同位素分离系数,p为有机相的锂/醚浓度比。从ΔG°(交换反应的自由能变化)和ε_p(p=100％时的富集系数)考察,有关体不分离锂同位素能力下降的次序为:穴醚(2,2,1)-CHCl_3/CF_3COOli-H_2O或穴醚(2,2,1)-树脂/LiI-甲醇,(4-叔丁基苯并-15-冠-5)-C_6H_5I/LiSCN-H_2O,(苯并-15-冠-5)-CHCl_3/LiI-H_2O。     

冠醚-金属离子配合物的构象转化、选择性和同位素效应的理论计算研究

冠醚能够选择性分离金属离子及其同位素，为实现快速选择高效的配体结构，本文采用密度泛函理论，以乙二醇二甲醚（DME）为模型化合物，对4种冠醚(9C3、12C4、15C5、18C6)同金属离子的配位作用进行系统计算研究。结果表明，金属离子与DME的结合可降低DME构象转化的能垒，降低的程度随金属离子电荷/半径比的增加而增大。金属离子与冠醚配位的同位素效应主要由金属同位素的相对质量差和配位键的键长决定，也和冠醚的构象有关。对同一金属离子 冠醚配合物，质量大的同位素配合物自由能较低，对于7Li和6Li，找到了Li 12C4具有同位素效应最大的构象。该工作为冠醚络合金属离子的理论计算中复杂的构象问题提供了简化而适用的分类方法，有利于更准确地计算金属离子 冠醚配合物的结合能，并为快速筛选高效分离金属离子及其同位素的冠醚配体提供了重要的理论依据。     

用于贫化锌分离的冠醚树脂合成及其特性研究

采用缩聚法自行合成了基于聚苯乙烯和二苯并-18-冠醚-6的PS@DB18C6冠醚树脂,并对其稳定性及吸附、解吸机理及特性进行了探究,而后进行了柱色谱法锌同位素分离实验。结果表明PS@DB18C6冠醚树脂在pH=7的丙酮溶液中具有较大的吸附容量,对锌离子的吸附模型为准一级动力学方程,在pH=3的α-羟基异丁酸(AHIB)溶液中的解吸满足一级动力学方程,且在吸附、解吸过程中能保持较好的结构稳定性;利用PS@DB18C6冠醚树脂通过柱色谱法能够有效实现锌同位素的分离,经过5 m色谱柱淋洗操作后,对⁶⁶Zn和⁶⁸Zn的最大前端富集值(β)分别为1.019 6和1.020 8。     

用大环聚醚分离锂同位素

孟山都研究公司的杰普森,1979年10月30日到11月2日于美国召开的能源利用方面的分离科学与分离工艺学的会议上,作了用大环聚醚进行锂同位素的化学交换的报告。作者测定了几个体系中富集锂同位素的两相     

简报

核放消息1 美国蒙德(Mound)实验室的B.E.Jepson用大环聚醚研究了锂同位素在有机相-水相间的化学交换,发现Cryptand(2,2,1)即穴醚(2,2,1)-LiTFA(HTFA)[HTFA为三氟乙酸]体系的单级分离因素a为1.041±0.006。这个数字虽稍低于锂汞齐-锂溶液体系的单级分离系数,但比一般锂有机相-水溶液的交换体系的分离系数高出不少。Jepson还发表了其它体系的单级分离系数如下:     

冠醚分离锂同位素工艺中锂的分光光度分析

本工作研究改进冠醚分离锂同位素工艺过程中水相和有机相中锂的分光光度分析法。以0.2%钍试剂为显色剂，用20%KOH溶液调节显色所需的强碱条件，试验获得了配合物在水 丙酮介质中的稳定显色。取样量为10μL时，锂含量在0.01~0.5g/L范围内符合比耳定律。水相样品锂测定值的相对标准偏差s_r为2.0%，有机相样品锂测定值的s_r为4.0%。     

Basic Characteristics of Centrifuges, (IV)

A method of numerically solving the convection-diffusion equation is presented for a binary isotopie gas mixture in the axisymmetric velocity field. A modified Newton's method is employed to perform the numerical integration without the assumptions that the pressure can be estimated from the rigid rotation model and the temperature of gas is uniform. A suitable form of the finite difference equation gives a computationally stable integration with reasonable representation of the molar concentration distribution of isotopie molecules in a rotating cylinder. The method includes a Gaussian elimination procedure which consists of the transformation of the Jacobian matrix to a triangular matrix followed by the backward elimination.

Computations are made on UF₆ gas in various centrifuges which have the openings for feed, product and waste on the end plates. Discussions are also presented on gas flows and separative efficiencies for the centrifuges which have baffle plates, skirting plates and bellows.     

Theory of Chromatographic Separation of Isotopes, (III)

A fundamental equation applicable to any kind of chromatography is solved on the assumption that velocity and chromatographic diffusion coefficient of the species under consideration are constant and its concentration is finite. The results can be used to describe the chromatographic behavior of the species in breakthrough, reverse breakthrough and band operations, covering not only the chromatographic distribution of isotopes but also that of easily separable chemical species, especially in the case of elution chromatography.

Some numerical calculations are performed to show how the shapes of the isotopie mole fraction and isotopie concentration profiles in band operation of a two-isotope chromatography are influenced by the velocity ratio and chromatographic diffusion coefficient ratio of the two isotopes, and by the initial band width. These calculations yield some interesting results, including a clear indication of the possibility of reverse enrichment.     

PVDF粉体预辐照接枝甲基丙烯酸缩水甘油酯制备锂离子二次电池隔膜研究

以聚偏氟乙烯（PVDF）粉体为基材,采用预辐照接枝方法,在PVDF粉体上用乳液聚合接枝甲基丙烯酸缩水甘油酯（GMA）,并采用溶液铸膜的方法制备了PVDF-g-PGMA膜。利用红外光谱（FTIR）,扫描电子显微镜（SEM）,压汞仪,电导率测试等分析表征手段对制备的PVDF—g-PGMA膜进行了表征。在氩气手套箱中组装成扣式电池,在电池测试系统上测试扣式电池的充放电循环性能。测试结果表明,在相同制备条件下,以PVDF-g-PGMA作为隔膜的锂离子电池性能优于以PVDF作为隔膜的锂离子电池性能。     

闪烁体的温度效应

本文介绍了测量闪烁体温度效应的装置及方法,给出了NaI(Tl)、CsI(Tl)、ZnS(Ag),锂玻璃,蒽及塑料等六种闪烁体的温度依赖关系,并着重对NaI(Tl)闪烁体的温度效应进行了分析。     

Gadolinium Isotope Separation by Cation Exchange Chromatography

Displacement chromatographies of Gd adsorption band in cation exchange resin were performed to observe the isotope effects in the Gd ion exchange processes involving complex forming reagents. The heavy isotope of ¹⁶⁰Gd was found to be enriched at the front boundary of Gd adsorption band and the lighter isotopes of 1MGd, ¹⁵⁶Gd and ¹⁵⁷Gd were enriched at the rear boundary in both cases of 20.1m elution with EDTA and 14 m elution with malic acid, as predicted in the theoretical relations. Observed separation coefficients are 4.9×10^?5, 4.0×10^?5 and 2.5×10^?5for isotopie pairs of ^{156 160}Gd, ¹⁵⁸Gd and ¹⁶⁰Gd, respectively, in the case of EDTA elution. In the case of malic acid elution, smaller separation coefficients were observed as 1.8×10^?5, 1.6 ⁵O^?5 and 0.92×10^?5 for isotopie pairs of ^{156 160}Gd, ¹⁵⁷Gd and^{158 160} respectively.     

硝酸钍与二并苯-24-冠-8的固体配合物的合成与性质

一、前言 具有环状空腔结构特征的冠醚类化合物,因其特殊的配合性质已日益引起人们的注意。近十余年来,“有关锕系元素冠醚配合物的研究虽有不少报道,但以往的研究工作所涉及到的主要是一些含醚氧原子数目小于7的冠醚。到目前为止,有关钍与含醚氧原子数目在7个以上的大空腔冠醚的固体配合物文献中尚未见报道。为此,我们对硝酸钍与二苯并-24-冠-8(简称DB24C8)的固态配合物的合成及性质进行了研究。     

Experiments at the T-11M device in support of the tokamak concept with closed Li cycle

The lithium emitter-collector concept, supposed the creation of steady state lithium circulation loop close the first wall and plasma periphery, seems as a solution of tokamak reactor first wall problem. This concept of renewable PFC (plasma facing components) has four characteristically steps: Li emission from PFC into the plasma (emitter), the boundary plasma cooling by non-coronal Li radiation, Li ions capture by collector before their deposit on a tokamak vessel wall and Li return from collector and first wall into emitter again. The main subject of the last T-11M experiments was investigations of the lithium collection by limiters. The lithium behavior in shadow of lithium limiter, based on the lithium filled CPS (capillary porous systems), was studied by the analysis of the witness-samples, and by use a mobile graphite probe. It was showed: (1) lithium deposit on the Li-limiter sides is proportional to the total Li emission from the lithium rail limiter (emitter). (2) Lithium deposit on the ion-drift side of Li-limiter to 3-5 times more as on electron side. (3) The total efficiency of Li collection by T-11M limiters can be 70 ± 20% of lithium integral emission from the lithium emitter during plasma operations while the theoretically limit can be 90%.     

Current status of the technology development on lithium safety handling under IFMIF/EVEDA

Studies for establishing technology for the safe handling of lithium was performed in the Engineering Validation and Engineering Design Activities (EVEDA) for the International Fusion Material Irradiation Facility (IFMIF). This research comprises four tasks: (a) extinguishing lithium files, (b) chemical reactions of lithium on the event of a leak, (c) lithium removal from the components, and (d) chemical analysis of impurities in lithium. Tasks (a) and (b), related to functions on the event of a lithium leak, involve selection of the material suitable for extinguishing lithium fires and assessment of corrosive effects of leaked lithium on materials at high temperature, respectively. Task (c) involves evaluation of methods for the replacement and/or decommissioning of the lithium components. Task (d) constitutes the development of high-precision techniques for the determination of impurities in lithium, particularly the dominating corrosive impurity—dissolved nitrogen. Experimental results addressing the objectives of each of the tasks are described in this communication.     

ABSTRACTS OF 1993 AESJ AWARDS

The UB3LYP/LanL2DZ level calculations were carried out for sixty-seven Li-M diatomic molecules of lithium between LiH and LiBi to explore the periodic properties of their ⁶Li-to-⁷Li isotopic reduced partition function ratios (rpfrs) and some other quantities. The Li-M bond distance, the frequency shift upon ⁷Li/⁶Li isotope substitution and the rpfr all show plots typical of any chemical and physical property which is a periodic function of the atomic number. The rpfr is strongly correlated with the Li-M bond stretching force constant except for LiH. The present calculations show that the rpfrs of diatomic molecules of group 2, group 12 and group 18 elements are relatively small, which reflects the filled electron shell and subshell characters of those elements. The results of the calculations and the consideration on chemical properties of elements suggest that zinc is a possible substitute for mercury in lithium isotope separation processes utilizing the redox reaction of lithium.     

功能化石墨烯吸附模拟反应堆冷却剂中银的研究

设计合成了四氧化三铁/石墨烯/聚乙烯亚胺复合材料（PMRGO），通过红外光谱、透射电镜、拉曼光谱和XPS等手段表征了PMRGO的化学组成和结构，并研究了该材料在模拟压水堆冷却剂环境下对银离子和银胶体的吸附性能。结果表明，PMRGO在模拟冷却剂条件下对银有良好的吸附性能，对银的吸附在pH=3~8范围内随pH值的升高而增大。随着银初始浓度的增大，PMRGO对银的吸附率逐渐升高。当银初始浓度为5 mg/L时，PMRGO对银离子吸附24 h后基本达到平衡，吸附量可达136 mg/g；对银胶体吸附30 min后基本达到平衡，吸附量可达169 mg/g。吸附等温线符合Langmuir方程，吸附动力学可用准二级动力学方程来描述。