Key Laboratory of Radiation Physics and Technology of the Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu, 610064, PR China.
China Institute for Radiation Protection, Taiyuan, 030006, PR China.
J Environ Radioact. 2023 Dec;270:107286. doi: 10.1016/j.jenvrad.2023.107286. Epub 2023 Aug 24.
The sorption behavior of U(VI) on Tamusu clay sampled from a pre-selected high-level radioactive waste (HLW) disposal site in Inner Mongolia (China) was studied systematically in the U(VI)-CO solution at pH 7.8 by batch experiments. The results demonstrated that the distribution coefficients (K) decreased with the increasing values of pH, [U(VI)], and ionic strength, but increased with the extended time and the rising temperature. The sorption was a pH-dependent, heterogeneous, spontaneous, and endothermic chemical process, which could be better described by Freundlich isothermal model and pseudo-second-order kinetic model. The presence of humic acid (HA) or fulvic acid (FA) significantly inhibited the U(VI) sorption, due to the enhanced electrostatic repulsion between the negatively charged HA/FA adsorbed on the clay surface and the negative U(VI) species, as well as the well dispersed HA/FA aggregates in solution wrapping the U(VI) species. The FTIR and XPS spectra indicated that the HCO groups on the surface of Tamusu clay after hydroxylation and the ‒OH groups in HA/FA were involved in the U(VI) sorption. The results reported here provide valuable insights into the further understanding of U(VI) migration in geological media.
研究了在 pH 值为 7.8 的 U(VI)-CO 溶液中，来自内蒙古预选高放废物处置场的塔木素黏土对 U(VI)的吸附行为。结果表明，分配系数（K）随 pH 值、[U(VI)]和离子强度的增加而降低，随时间的延长和温度的升高而增加。吸附是一个依赖于 pH 值的、非均相的、自发的和吸热的化学过程，更能被 Freundlich 等温模型和拟二级动力学模型描述。腐殖酸（HA）或富里酸（FA）的存在显著抑制了 U(VI)的吸附，这是由于带负电荷的 HA/FA 吸附在粘土表面上与带负电荷的 U(VI)物种之间的静电排斥增强，以及在溶液中良好分散的 HA/FA 聚集体包裹了 U(VI)物种。FTIR 和 XPS 谱表明，塔木素黏土表面经羟化后的 HCO 基团和 HA/FA 中的‒OH 基团参与了 U(VI)的吸附。本研究结果为进一步了解 U(VI)在地质介质中的迁移提供了有价值的见解。
