【作者】 雷云逸；

【导师】 曹卫国；

【作者基本信息】 上海大学 ， 环境工程， 2019， 博士

【摘要】 溶剂萃取法是乏燃料后处理技术中浓缩与提纯U（VI）的重要方法之一,新萃取剂的研究和工艺流程的研究是溶剂萃取技术的两个重要方面。本文用氟原子取代二（2-乙基已基）丁酰胺（DEHBA）的丁酰基碳链上的氢原子,得到作为U（VI）、Th（IV）的新萃取剂二（2-乙基己基）全氟丁酰胺（DEHFBA）。首次研究了DEHFBA在硝酸介质中对U（VI）、Th（IV）的萃取性能,得到了比较好的实验结果。本论文同时研究了用天然植物茶叶渣对U（VI）、Th（IV）的吸附性能,发现茶叶渣对钍、铀有较好的吸附萃取效果,这对乏燃料后处理及矿山污染的处理,有很好的应用价值。本论文主要内容包括以下几个方面:1、以全氟丁酰氯、二异辛胺合成新萃取剂二（2-乙基己基）全氟丁酰胺（DEHFBA）,并用红外光谱、核磁共振谱等手段对DEHFBA的结构进行了表征。2、研究了新萃取剂DEHFBA在硝酸介质中对U（VI）、Th（IV）的萃取行为,考察了萃取时间、稀释剂、萃取剂浓度、硝酸酸度、萃取温度等因素对萃取分配比的影响,本文选择比较廉价的苯作稀释剂,有利于DEHFBA稳定萃取;DEHFBA在硝酸介质中对U（VI）的萃取,要求p H越高越好,考虑到铀酰离子的水解条件,选择最佳萃取条件p H为3左右;DEHFBA在硝酸介质中对Th（IV）的萃取,酸溶液浓度在2～3 mol/L左右效果稍好。DEHFBA对U（VI）的有一定的萃取力,对Th的萃取力相对较弱。3、初步推断了DEHFBA对U（VI）、Th（IV）萃取机理,得出DEHFBA与UO₂（NO₃）₂的萃合物为UO₂（NO₃）₂·DEHFBA,分配比的对数与萃取剂浓度的对数两者之间的关系,斜率为非整数的直线关系,推测也可能有2UO₂（NO₃）₂·DEHFBA存在;DEHFBA与Th（NO₃）₄的萃合物为Th（NO₃）₄·DEHFBA,也可能有2UO₂（NO₃）₂·DEHFBA同时存在。研究得出DEHFBA对U（VI）、Th（IV）的萃取过程属于吸热过程。研究还发现,金属离子初始浓度低于0.0004 mol/L时,DEHFBA的萃取U性能稍优于DEHBA、TBP,但金属离子初始浓度高于0.0004 mol/L,DEHFBA的萃取性能并没有优越性。4、研究了DEHFBA的辐照稳定性,分析对比辐照前后DEHBA、DEHFBA对U（VI）的萃取行为,从萃取平衡时间、萃取剂浓度、水相酸度、金属离子浓度、萃取温度等因素考察分配比变化,结果表明,DEHFBA相比DEHBA具有更好的辐照稳定性。5、利用串级实验原理,研究了DEHFBA在硝酸介质中对U（VI）、Th（IV）的分离,得出优先考虑萃取U（VI）有利于两者分离。当U（VI）中含微量Th（IV）,浓度比例为19:1时,可以达到较好的萃取分离;而当Th（IV）中含微量U（VI）,浓度比例为9:1时,即可达到很好的分离。6、探讨了红、绿茶渣对U（VI）、Th（IV）吸附性能,研究了在硝酸介质中,吸附剂剂量、吸附时间、水相酸度、吸附温度等因素对红、绿茶渣吸附性能的影响。得出两种茶叶对U（VI）、Th（IV）的吸净率都能达到98%以上,在U（VI）的吸附研究过程中,绿茶渣比红茶渣容易达到吸附平衡,红茶渣对U（VI）的最大吸附量为70.094μg/mg,绿茶渣对U（VI）的最大吸附量为62.078μg/mg,在吸附过程中红茶渣表现出比绿渣更好的吸附性能。红、绿茶渣吸附U（VI）、Th（IV）的红外光谱分析研究,得出红、绿茶渣中的羰基和羟基及氨基表现出交换与络合。分析了红、绿茶对U（VI）、Th（IV）吸附的吸附模型,得出Freundlich等温吸附模型能更好地描述U（VI）,Th（IV）在红茶渣上与绿茶渣上的吸附行为。更多还原

【Abstract】 The solvent extraction method is one of the important techniques in concentrating and purifying uranium（VI）.The research and processing of new extractant are two important aspects of solvent extraction technology.In this paper,N,N-di（2-ethylhexyl）-2,2,3,3,4,4,4-heptafluorobutan-amide（DEHFBA）was prepared and evaluated by the extraction and separation of U（VI）and Th（IV）.The results indicated that DEHFBA exhibited high extraction efficiency and distribution ratios of U（VI）and Th（IV）in nitric acid media.And the extraction of U（VI）and Th（IV）by using natural plant tea residue as an adsorbent was also investigated.The main contents are as follows:1)In this work,N,N-di（2-ethylhexyl）-2,2,3,3,4,4,4-heptafluorobutanamide（DEHFBA）was synthesized and identified by ¹H NMR,¹⁹F NMR and IR spectroscopy2)The effects of diluents,extractants,metal ions and nitric acid acidity on the extraction distribution ratios of uranium extraction and extraction rate have been explored.DEHFBA shows much better irradiation stability and extraction performance for UO₂²⁺from nitric acid media at low acidity than N,N-di（2-ethylhexyl）butanamide（DEHBA）and tributylphosphate（TBP）.DEHFBA can extract U（VI）in some extent,but has a poor extraction ability for Th（IV）.3)The extraction mechanism of DEHFBA extraction performance for U（VI）and Th（IV）is discussed.The extractant compounds might consist of UO₂（NO₃）₂·DEHFBA for U（VI）and Th（NO₃）₄·DEHFBA for Th（IV）.4)The irradiation stability of two uranium extractants,DEHBA and DEHFBA,and the effect of irradiation on the extraction efficiency of both extractants were studied.The extraction behavior of uranium（VI）by DEHBA and DEHFBA in nitric acid medium with benzene as solvent before and after irradiation was studied.The effects of extraction concentration,metal ion concentration,metal ion solution acidity and extraction temperature on the distribution ratio of uranium（VI）were also studied.The results show that DEHFBA showed better irradiation stability than DEHBA and was less sensitive to the change of extraction conditions.5)The separation of U（VI）and Th（IV）from DEHFBA in nitric acid medium was studied by using the principle of cascade experiments.It is concluded that when the trace Th in a large amount of UO₂²⁺is reached and the ratio is 19:1,it can be well separated.When a trace of UO₂²⁺is found in a large number of Th（IV）and the ratio is 9:1,a good separation can be achieved.6)The adsorption stability of two kinds of uranium adsorbents,black tea residue and green tea residue,was studied.The effects of adsorbent concentration,adsorption time,uranium ion concentration,uranium ion solution acidity and adsorption temperature on the adsorption behavior of U（VI）by red and green tea residue in nitric acid medium were studied.The adsorption models of U（VI）on red and green tea were analyzed.The Freundlich isothermal adsorption model can better describe the adsorption behavior of U（VI）on black tea residue and green tea residue.更多还原