Geochemistry and thermodynamics of transuranium elements in ultrafine interstice under deep geosphere.

研究地圈中镧系元素和放射性元素的化学行为，对于高放废物处置的安全评估具有重要意义。然而，由于在水溶液中很难区分金属离子和胶体金属，所以很难确定镧系元素和氡系元素的形态。激光诱导击穿光谱(LIBS)可以同时检测水溶液中的离子和金属微粒，特别是对微粒具有高灵敏度。在本研究中，我们用LIBS分析了水溶液中的Eu(III)离子和Eu_2O_3粒子，并测量了Eu(III)在水溶液中的水解行为。此外，我们还尝试检测了Eu(III)离子吸附在二氧化钛颗粒上的等离子体发射，在Eu(III)水溶液和Eu_2O_3悬浮溶液中，在420.505 nm处观察到了Eu的等离子体发射。发射谱线一般用于Eu的定量分析。Eu_2O_3的等离子体发射强度高于…当Eu浓度相同时，Eu(III)离子的吸收带大于Eu(III)离子，在Eu(III)水溶液的LiBS光谱中观察到Eu(III)离子的吸收带。这些结果表明，LIBS可以将水溶液中的Eu(III)离子和Eu_2O_3粒子区分开来，Eu的等离子体发射强度随着Eu浓度的增加而增加。Eu(III)离子和Eu_2O_3颗粒在低浓度范围(Eu(III)离子和Eu_2O_3粒子的浓度分别约为10^~10^lt；-2~10^&lt；-1~10^&lt；-1~10^&lt；-5&gt；~10^&lt；-4&gt；~(-4)mol/dm^3)呈良好的线性关系。Eu的等离子体发射强度随Eu(III)水溶液的pH增大而增大，在pH=6以上发射强度急剧增加。这一趋势与Sm(OH)_3的溶解度曲线相似。从Eu(III)离子吸附在二氧化钛表面的等离子体发射中发现，LIBS只能检测到二氧化钛表面的Eu(III)离子，因为没有观察到Eu(III)离子在溶液中的发射。我们还尝试使用时间分辨LIBS来分析Eu(III)离子的吸附形式。《稀土物理与化学手册》第15卷《爱思唯尔科学》(1991)431

Investigation of the chemical behavior of lanthanides and actinidesin the geosphere is important for the safety assessment of high-level radioactive waste disposal. However, determination of speciation for lanthanides and actinides is difficult, because it is too hard to distinguish between metal ion and colloidal metal in aqueous solution. Laser-induced breakdown spectroscopy (LIBS) can detect both ions and microparticles of metals in aqueous solution, especially, high-sensitive to microparticles. In this study, we analyzed Eu(III) ion and Eu_2O_3 particle in aqueous solution by LIBS, and measures the hydrolysis behavior of Eu(III) in aqueous solution. Furthermore, we tried to detect the plasma emission of Eu(III) ions sorbed on TiO_2 particles.Plasma emission of Eu was observed at 420.505 nm both in Eu(III) aqueous solution and in Eu_2O_3 suspended solution. The emission line was generally used for quantitative analysis of Eu. The plasma emission intensity of Eu_2O_3 was higher than … More that of Eu(III) ions when Eu concentration was same, and absorption band of Eu(III) ions was observed in LIBS spectrum of Eu(III) apeous solution. These results indicated Eu(III) ions can be distinguished from Eu_2O_3 particles in aqueous solution by LIBS.The plasma emission intensity of Eu increased with Eu concentration. The intensity vs. concentration plot showed a good linearity in low concentration range (approximately 10^<-2> to 10^<-1> mol/dm^3 and 1O^<-5> to 10^<-4> mol/dm^3 for Eu(III) ions and Eu_2O_3 particles, respectively).The plasma emission intensity of Eu increased with pH of Eu(III) aqueous solution, and drastic increase of emission intensity was observed above pH=6. The tendency was similar with solubility curve of Sm(OH)_3, which calculated using stability constants in litrature[1]. This result suggested that LIBS is useful for measurement of hydrolysis and precipitation behavior of Eu(III) in aqueous solution.From plasma emission of Eu(III) ions sorbed on TiO_2 particles, it was found that only Eu(III) ions on TiO_2 may be detected by LIBS.because the emission from Eu(III) ions in solution was not observed. We also have tried to use time-resolved LIBS to analyze sorption form of Eu(III) ions.[1] K.A.Gschneider, Jr., L.Eyring, eds. "Handbook on the Physics and Chemistry of Rare Earths, Vol.15" Elsevior Science (1991) 431 Less