放射性核素Eu(III)在锰(氢)氧化物上的吸附机理和微观结构研究

The sorption mechanism and microstructure of long-term lanthanides(III) and actinides(III) radionuclides on the surfaces of suspension particles is prerequisite to the assessment of their potential hazardous towards ecological environment and human beings. Therefore, in this project, a mechanistic understanding of Eu(III) sorption at the manganese (hydr)oxides/water interface is to be investigated based on macroscopic physiochemical and high resolution EXAFS spectroscopic techniques. The effects of contact time, pH, and temperature on Eu(III) sorption on manganese (hydr)oxides are to be studied by using batch techniques, the sorption kinetics and thermodynamics parameters, and the effects of water chemistry on sorption can be obtained. The fluorescence peak of Eu(III) from that of manganese (hydr)oxides, whose fluorescence peaks are too close in energy to be discriminated by the conventional EXAFS technique, can be discriminated by the utility of high resolution EXAFS technique. Thus, the EXAFS spectra of Eu(III) adsorbed on the surface of manganese (hydr)oxides can be determined. Based on the analysis of the EXAFS spectra, the sorption mechanism and microstructure Eu(III) adsorbed on manganese (hydr)oxides can be observed. The relationship of the compositon, structure and surface functional groups of manganese (hydr)oxides and their sorption property towards Eu(III) can be disclosed. The findings in this project are important to describe radionuclide interaction with suspension particles at molecular level and will help provide valuable data for the nuclear waste treatment.

在放射性废水的处理中，研究长寿命放射性镧系、锕系元素在悬浮颗粒物/水界面的吸附和微观结构，对评估放射性核素对生态环境和人类健康造成的潜在危害具有重要意义。本项目拟利用静态法和高分辨EXAFS技术研究放射性核素Eu(III)在悬浮颗粒物的重要组分锰(氢)氧化物/水界面的吸附作用和微观机理。用静态法研究时间、pH和温度等水化学条件对锰(氢)氧化物吸附Eu(III)的影响，获得吸附动力学和热力学参数，阐明水化学条件对吸附的影响机制；用高分辨EXAFS技术克服常规EXAFS技术的缺陷，分辨出Eu Lα1和Mn Kα荧光信号，测得吸附在锰(氢)氧化物上Eu(III)的EXAFS谱并通过图谱解析，明确Eu(III)在不同晶型的锰(氢)氧化物上的吸附机理和微观结构。从宏观和微观两个方面揭示锰(氢)氧化物的组成、结构和表面官能团与其吸附Eu(III)之间的内在关联机制，为放射性污染治理提供有意义的指导。

本项目将常规光谱技术、批实验、高分辨X-射线吸收精细结构技术相结合的研究方法，深入探讨了放射性核素Eu(III)在锰(氢)氧化物/水界面的吸附机理和微观结构。首先，利用化学法合成 了δ-MnO2, β-MnO2, γ-MnOOH等典型不同晶体结构的锰(氢)氧化物。采用批平衡技术考察了Eu(III)在锰(氢)氧化物上的吸附和水化学条件对吸附的影响，揭示了Eu(III)在锰(氢)氧化物/水界面的吸附动力学和热力学规律。采用高分辨EXAFS技术研究了Eu(III)在锰(氢)氧化物上的吸附机理和微观构型，剖析了锰(氢)氧化物的组成和结构与其对Eu(III)的吸附和微观结构之间的内在规律，阐明了吸附剂特性和吸附性质的关联机制。此外，项目还探讨了钛酸纳米管对Ni(II), Eu(III), Th(IV)等不同价态的放射性核素的吸附性能、微观作用机制及其环境去污应用潜力，探明了钛酸纳米管对不同价态放射性核素去除能力的差异及不同环境条件下不同的微观作用机制。这些研究结果对从分子水平上揭示放射性核素在颗粒物/水之间的界面作用机理有重要的参考指导意义，为放射性核素进行危害评估以及有效治理提供了有关的理论基础和数据支持。在项目的支持下，在The Journal of Physical Chemistry A, Chemosphere, Carbon, Chemical Engineering Journal, Applied Catalysis B: Environmental, Radiochimica Acta等国际SCI刊物上发表了10多篇相关研究论文，至今总被引频次达到150次，研究结果引起了国内外同行的关注和重视。