新型有序大孔SiO2连续吸附分离TBP和铀的性能及机理研究

The separation of tri-n-butyl phosphate (TBP) and uranium of low concentration in the plutonium recovery section of the PUREX process is one of the key scientific problems in spent fuel reprocessing. As the adsorption technique is effective, various resins are used to separate TBP and uranium, respectively. However, resins have several defects such as weak thermal and irradiation stability, and overcommitting. The project here intends to develop novelly ordered-macroporous silicon dioxide materials for the efficiently continuous separation of TBP and uranium. The theory and method of structural chemistry will be adopted to design and optimize the preparation of ordered-macroporous silicon dioxide materials with the aim of improving the diffusion speed and complexation efficiency of TBP and uranium. The effect of the template size, the solution composition of tetraethyl orthosilicate and calcination procedure on the pore structure and functional group amount is to be studied. The influence of solid-liquid ratio, contact time, temperature and initial concentration on the adsorption will be explored. The mechanism of continuous adsorption of TBP and uranium will be explored by using Langmuir, Freundlich and pseudo-first order, pseudo-second order kinetics, spectrum and energy spectrum. The project will provide a scientific basis for the continuous separation of TBP and uranium in spent fuel reprocessing.

PUREX流程钚尾端中低浓度磷酸三丁酯（Tri-n-butyl phosphate，TBP）和铀的分离是乏燃料后处理中关键的科学问题之一。吸附法是一种有效的分离技术，然而当前采用不同类型树脂吸附TBP和铀，存在树脂热稳定性弱、辐照稳定性差、使用量大等问题。本项目拟开发新型有序大孔二氧化硅材料，用于连续高效分离TBP和铀。研究采用结构化学的理论与方法，设计、优化有序大孔二氧化硅的制备，提升TBP和铀在材料内的扩散速度和络合效率；研究模板尺寸、正硅酸四乙酯溶液配比等、煅烧程序对二氧化硅孔径、孔道结构、官能团含量等的影响；探索固液比、接触时间、温度、初始浓度等对吸附影响；采用朗格缪尔、弗雷德里希和准一级、二级动力学、波谱和能谱等研究连续吸附TBP和铀。该项目为乏燃料后处理中连续分离TBP和铀提供科学依据。

随着核电的发展，铀资源的短缺和含铀废水的危害日益凸显。因此，无论是从资源回收利用或是环境保护的角度，以经济、环境友好的方式从水中吸附铀都具有重要的科学意义和现实意义。有序孔道可以提升离子传输速度，有利于吸附剂吸附铀。本项目开发了采用了气固转换法合成了磺化介孔聚合物FDU-15-SO3H/t，通过硝基还原法制备了带有氨基的中孔碳(MC-NH2)，通过模板法和后负载技术开发了超分子/有序介孔二氧化硅，研究了其对铀、铯的吸附行为，阐释了酸度、固液比、接触时间、温度、初始浓度等对吸附影响；采用等温模型、动力学模型、热力学模型、波谱和能谱等研究吸附机理。MC-NH2的氨基含量为1.25 mmol/g。MC-NH2吸附U(VI)受pH影响，最大吸附发生在pH 5.0时。MC-NH2对U(VI)最大吸附量达到385.98mg/g，吸附符合准二级动力学模型，为化学反应。0.1mol/L EDTA溶液对负载U(VI)的MC-NH2洗脱性能最佳洗脱液，洗脱效率达到99.32%。pH=5.0是FDU-15-SO3H吸附U(VI)的最佳pH值，吸附符合准二级动力学模型，为化学反应。吸附符合Langmuir模型，最大吸附量95.60 mg/g。热力学参数(ΔH>0，ΔS>0，ΔG<0)表明，吸附为吸热、自发、固液表面无序度增加的过程。超分子/有序介孔二氧化硅的孔径为194.2nm，其吸附铯的最佳pH为6，吸附符合准二级动力学模型，为化学反应。吸附符合Langmuir模型，最大吸附量150.01mg/g。吸附为吸热过程，增加温度有利于吸附。该项目研究结果为从乏燃料后处理酸液中分离铀、铯提供了数据与理论支撑。