Institute of Physical Chemistry, National Centre for Scientific Research Demokritos 153 10 Ag Paraskevi, Athens, Greece.
J Hazard Mater. 2009 Nov 15;171(1-3):1024-31. doi: 10.1016/j.jhazmat.2009.06.118. Epub 2009 Jun 27.
In this work, a study of the leaching kinetics of Cs(+) ions from cement paste solids, containing inactive Cs(2)SO(4), is presented, involving (i) the parallel performance of leaching experiments at two temperatures (30 degrees C and 70 degrees C); (ii) the performance of leaching tests with intermediate changes in temperature between 30 degrees C and 70 degrees C; (iii) the use of specimens of two different thicknesses and (iv) the determination of the distribution of Cs(+) in the cement specimen at various stages of the leaching test. The results of leaching studies at 30 degrees C with cement solids simulating the composition of real radioactive wastes, containing NaNO(3), small amounts of inactive CsNO(3) and traces of (137)Cs(+) are also reported. Concentration profiles of Cs(+) in inactive specimens showed that part of the Cs(+) (20-30%) tends to be immobilized in the matrix, while elution of the readily leachable portion follows Fick's law reasonably well. No immobilized Cs(+) was detected in the samples containing considerable amounts of NaNO(3). Long-term leaching experiments (up to 8 years) revealed acceleration of the elution process (not detectable in short-term tests), attributable to increase in porosity caused by erosion of the cement matrix. Sorption experiments of Cs(+) ions by cement granules indicated that adsorption on cement pore surfaces is not significant. On the other hand, the leaching tests at two different temperatures or with intermediate changes in temperature between 30 degrees C and 70 degrees C, yielded activation energies that indicated a more complicated kinetic behavior.
本工作研究了含惰性 Cs2SO4 的水泥固化体中 Cs(+)离子的浸出动力学，涉及：(i) 在 30°C 和 70°C 两个温度下进行浸出实验；(ii) 在 30°C 和 70°C 之间进行中间温度变化的浸出实验；(iii) 使用两种不同厚度的样品；(iv) 在浸出实验的不同阶段测定 Cs(+)在水泥样品中的分布。还报告了在 30°C 下用模拟真实放射性废物组成的水泥固体进行浸出研究的结果，其中含有 NaNO3、少量惰性 CsNO3 和痕量 (137)Cs(+)。惰性样品中 Cs(+)的浓度分布表明，部分 Cs(+)（20-30%）趋于固定在基质中，而可溶部分的洗脱基本符合菲克定律。在含有大量 NaNO3 的样品中未检测到固定的 Cs(+)。长达 8 年的长期浸出实验表明，洗脱过程加速（在短期实验中不可检测到），归因于水泥基质侵蚀导致的孔隙率增加。水泥颗粒对 Cs(+)离子的吸附实验表明，在水泥孔表面的吸附并不显著。另一方面，在 30°C 和 70°C 之间的两个不同温度下或中间温度变化下进行的浸出实验，得到的活化能表明了更复杂的动力学行为。
