水溶液中痕量镅在容器壁上的吸附研究

【作者】 肖成建；

【导师】 陈银亮；

【作者基本信息】 中国工程物理研究院 ， 核燃料循环与材料， 2005， 硕士

【摘要】 在放射化学的研究中,研究放射性物质在容器壁上的吸附是一件非常有意义的工作。由于影响因素复杂,实验结果不好重复,使得容器壁的吸附是一个不定因素,目前只能得到定性的推测。 本文首先用静态浸泡的方法,研究四种不同材质（硬质玻璃、石英、聚乙烯、聚四氟乙烯）的容器壁对水溶液中痕量镅(²⁴¹Am（Ⅲ）)的吸附。实验结果表明,不同材质的容器壁经过不同方法处理后,吸附均有所差异。所选容器壁材质中,聚四氟乙烯的吸附能力最小,聚乙烯的吸附能力最大;所用处理方法中,硅烷化能有效减少器壁吸附。 针对放化实验操作中广泛使用的玻璃器皿,本文用玻璃微球表面模拟容器壁,即用一定量的玻璃微球作吸附剂,采用浸泡—振荡的方法,系统地研究不同溶液介质条件下镅在玻璃表面上的吸附。实验研究表明,溶液介质条件对吸附的影响非常显著:降低溶液温度、降低pH值、增大离子强度、选择离子价态高的电解质(如Al³⁺)和络合能力强的络合剂（如F^-）均能有效减少镅的吸附。因此,在放化分离纯化镅流程里的一个水相体系中（1mol/L Al（NO₃）₃+4mol/L NaNO₃+0.1mol/L HNO₃）,即便玻璃的表面积增大到50.25m²,玻璃表面上也没有镅的吸附损失。 采用Lagergren一级动力学方程和BAM理论的液膜扩散方程描述了Am（Ⅲ）在玻璃—水溶液界面上的吸附过程;热力学计算得到吸附热ΔH=17.2±1.8kJ/mol,表明Am（Ⅲ）在玻璃—水溶液界面上的吸附为一个吸热的过程。通过综合分析上述实验结果,从微观络合模式的角度建立了玻璃表面的Stern双电层模型,合理地阐释了不同溶液介质条件下镅在玻璃表面上的吸附现象。 本文的研究结果可以为如何有效地减少或避免放射性物质在容器壁上的吸附损失,以及预示其它三价镧锕元素的吸附性质,提供实验方法和依据。更多还原

【Abstract】 Researching the adsorption of radioelements on container walls is very significant in radiochemistry. In that the influence factors are complicated, laboratorial results are difficult for repetition, so adsorption on container walls is uncertain, and is guessed by qualitative analysis.In this paper, the adsorption of traced ²41Am（III） on four kinds of container walls in aqueous solution is studied, using static dunking. The results show that the value of sorption is different for different container walls. Among the four kinds of materials, teflon has a least sorption ratio. In the three washing ways, silanization of glass walls is the best way to reduce the adsorption of ²41Am（III） on container walls.Because glass vessels are used widely, tiny glass balls are used to simulate container walls, and the rule of glass surface adsorbing ²41Am（III） in aqueous solution is investigated under different aqueous medium conditions by means of dunking and shaking. It is found that glass surface adsorbing ²41Am（III） in aqueous solution is influenced greatly by aqueous medium conditions. The adsorption is decreased with increasing acidity, ionic strength, using inorganic complexant with more activity, and falling temperature. So, in a solution of the separating-purifying Americum process,which consists of 1mol/L Al （NO₃） 3,4mol/L NaNO₃ and 0.1mol/L HNO₃, there is no adsorption happened,even if surface area of glass balls is added up to 50 square meters.Lagergren first-order kinetic equation and the film diffusion equation of BAM theory can describe the adsorbing process of Am （III） on the glass surface. Enthalpy of sorption is 17.2 ± 1.8kJ/mol,which indicates a endothermic reaction. Combining all of the experimental results, Stern double layer model is established, which can interpret the rule of glass surface adsorbing ²41Arn（III） under different aqueous medium conditions in reason.Research above may offer academic base and ways to reduce the adsorption of radioelements on container walls, and foreshow adsorbing characters of other tervalent actinides or lanthanides in radiation chemistry.更多还原