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Separation of rare earth metal elements by electromigration in melts

熔体中电迁移分离稀土金属元素

基本信息

批准号：
03453046
负责人：
OKADA Isao
金额：
$ 3.26万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

In order to clucidate the mechanism of electric conduction in molten salts, the internal mobilities of rare carth chloride melts have been measured by a countercurrent electromigration method. If there is an appreciable difference in the mobilities among the rare earth elements, countercurrent electromigration may be used for separation of these elements. Then, this method is expected to be useful particularly for reprocessing of the nuclear fuels. We have performed the following experiments.In the molten mixture system (Y, La)Cl_3 relative differences in internal cation mobilities have been measured at 1073 K by a countercurrent electromigration method. The electric conductivities of the mixture system have been measured. From these data the internal cation mobilities b of Y^<3+> and La^<3+> have been calculated. At all the concentrations La^<3+> is more mobile than Y^<3+> by 20-30 %. This is presumably because the interaction for Y-Cl pair is stronger than that for La-Cl pair. Thus, … More this method is applicable for separation of these ions. while the ionic radius of Y^<3+> (0.900 A) is distinctively smaller than that of La^<3+> (1.032 A), the molar volume of pure LaCl_3 is slightly smaller than that of pure molten YCl_3. This suggests that the structure of these melts is considerably different. In the mixture system, both b_Y and b_<La> decrease with increasing molar volume, the trend of which is the same as that in other systems such as monovalent and divalent cation systems.By a similar method b's in the mixture system (Y, Dy)Cl_3 have been measured. In this case the ionic radii of the two cations are nearly the same, that is 0.900 A for Y^<3+> and 0.912 A for Dy^<3+>. b_Y is appreciably greater than b_<Dy>. Thus, it can be conjectured that, when the ionic radii are nearly the same, the difference in the masses (Y : 88.9059 and Dy : 162.50) plays a role.The isotope effect in b of Dy^<3+> has veen studied in pure DyCl_3 also by countercurrent electromigration. The mass numbers of the main stable Dy isotopes are 160(2.34 %), 161(18.9 %), 162(25.5 %), 163(24.9 %) and 164(28.2 %). The value of the mass effect defined as mu=( b/b)/( M/M) is about -0.030 nearly independent of temperature in the range 973 K-1043 K, whose absolute value is relatively large.In conclusion, electrically-conducting species in rare earth chlorides are conjectured to be monoatomic ions and countercurrent electromigration method in molten systems can be used for separation of rare earth metals. Less

为了阐明熔盐导电机理，用逆流电迁移法测定了氯化稀土熔体的内迁移率。如果稀土元素之间的迁移率存在明显差异，则可以使用逆流电迁移来分离这些元素。因此，这种方法预计特别适用于核燃料的再处理。我们进行了以下实验：在熔融混合物体系（Y，La）Cl_3中，用逆流电迁移法测量了1073 K时内阳离子迁移率的相对差。测定了混合体系的电导率。根据这些数据计算了Y^<3+>和La^<3+>的内离子迁移率B。在所有浓度下，La^<3+>的移动的比Y^<3+>多20- 30%。这可能是因为Y-Cl对的相互作用比La-Cl对强。因此，在本发明中， ...更多信息该方法适用于这些离子的分离。而Y^<3+>的离子半径（0.900）明显小于La^<3+>的离子半径（1.032），纯LaCl_3的摩尔体积略小于纯YCl_3的摩尔体积。这表明这些熔体的结构是相当不同的。在混合体系中，B_Y和B_s均<La>随摩尔体积的增大而减小，其趋势与其它体系如一价和二价阳离子体系相同，用类似的方法测定了（Y，Dy）Cl_3中的B_s。在这种情况下，两种阳离子的离子半径几乎相同，Y^<3+>和Dy^<3+>的离子半径分别为0.900和0.912。B_Y明显大于B_<Dy>。因此，当离子半径相近时，Dy ^（3+）的质量差（Y：88.9059和Dy：162.50）起作用.本文还用逆流电迁移法研究了纯DyCl_3中Dy^（3+）的B同位素效应. Dy主要稳定同位素的质量数为160（2.34%）、161（18.9%）、162（25.5%）、163（24.9%）和164（28.2%）。在973 K ~ 1043 K范围内，质量效应μ =（B/B）/（M/M）约为-0.030，其绝对值较大，与温度几乎无关，表明稀土氯化物中的导电物种为单原子离子，熔融体系逆流电迁移法可用于稀土金属的分离。少