Application of LIBD to the determination of the solubility product of thorium(IV)-colloids

被引:62
作者
Bundschuh, T [1 ]
Knopp, R [1 ]
Müller, R [1 ]
Kim, JI [1 ]
Neck, V [1 ]
Fanghänel, T [1 ]
机构
[1] Forschungszentrum Karlsruhe, Inst Nukl Entsorgungstech, D-76021 Karlsruhe, Germany
关键词
laser; breakdown detection; colloid formation; thorium dioxide; solubility product; particle size;
D O I
10.1524/ract.2000.88.9-11.625
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
A new experimental method is presented for the determination of solubility data, which is based on the laser-induced breakdown detection (LIBD). The method is capable of monitoring the initial colloid generation when the metal ion concentration reaches or just exceeds the solubility at given pH. The application is made to determine the solubility of Th(IV) in acidic solutions at I = 0.5 M (NaCl) and 25 degreesC. The initial colloid formation is determined as a function the Hf concentration in a series of 2.8 x 10(-2)-8.9 x 10(-5) M thorium solutions. The conditional solubility product (log K-sp' = -49.54+/-0.22) obtained in this study corresponds to an equilibrium between solution and colloidal thorium dioxide particles. The solubility product at I = 0 (log K-sp(o) = -52.8+/-0.3) is calculated with the SIT coefficients of the NEA-TDB. It corresponds to the known value for crystalline ThO2(cr), in particular if the small particle size of about 20 nm is taken into account. The present results indicate that the high thorium solubilities measured in the previous studies for amorphous Th(IV) hydroxide or hydrous oxide are primarily caused by the inclusion of polynuclear species or Th(IV) colloids of very small size.
引用
收藏
页码:625 / 629
页数:5
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