偕胺肟基聚丙烯腈纤维的制备及其对铀酰和竞争离子吸附性能研究

发布时间：2018-02-14 05:36

本文关键词： 海水提铀铀酰离子吸附材料偕胺肟基凝胶层　出处：《中国科学院研究生院（上海应用物理研究所）》2015年硕士论文　论文类型：学位论文

【摘要】：由于陆地上铀资源非常有限，为满足日益增长的核能燃料的需求，人们从上个世纪50年代以来开始着手海水提铀的研究工作。经过不懈的努力和尝试，学者们发现吸附法是最有工业前景的海水提铀方法。吸附材料中偕胺肟基系列化合物是目前公认性能最好的吸附材料。偕胺肟基团是决定偕胺肟类材料吸附性能的关键功能基团，腈基转化率（CR）及偕胺肟基团密度（AOGD）是两个重要的指标。材料的吸附性能与偕胺肟基团的含量，以及与偕胺肟化制备过程中材料的一些微观变化的关系，应该成为海水提铀研究中值得深入探讨的问题。一般认为，材料中偕胺肟基团含量的增多，应该成为提升材料的吸附性能的一个主要途径。然而本论文认为，当材料的偕胺肟基含量达到一定程度，会引起材料形貌和性能的变化，并不再对吸附性能的提高有利，甚至形成阻碍。因此本论文的意义及目的就在于研究CR及AOGD与吸附性能的关系，探索规律，以期为海水提铀用吸附材料的进一步发展提供参考。本论文的研究内容主要包括两部分，首先是聚丙烯腈（PAN）纤维偕胺肟化反应的规律研究，以及对其形貌和性能的表征。选用聚丙烯腈（PAN）纤维作为基材，与羟胺进行偕胺肟化反应制备得到偕胺肟基聚丙烯腈（AO-PAN）纤维，讨论了诸如反应时间、温度、羟胺浓度、溶剂配比和体系pH等因素对AO-PAN纤维的CR及AOGD的影响。结果表明，反应时间增长，温度升高，羟胺浓度增大均在一定程度上对CR和AOGD的提高有利，达到某一程度后，CR及AOGD便不再增加，趋于平衡；中性条件最有利于偕胺肟化反应；当CR超过10.8%之后，随着CR的继续升高，纤维会变得收缩结块，由柔软变得脆硬。利用电子扫描显微镜及光学显微镜对AO-PAN纤维进行了形貌表征，发现CR较高的单丝纤维有弯曲现象，但纤维表面并没有明显的裂痕或其他破损现象；AO-PAN纤维在水中浸泡后会在表面形成一层水凝胶，凝胶层的厚度会随CR及AOGD的升高而不断增大。利用电子单丝拉力测试仪及动态热机械分析仪（DMA）对AO-PAN纤维的力学性能进行了表征，结果发现，经过偕胺肟化反应后的纤维的机械强度有所下降，原PAN纤维的断裂强度为7.1cN/dTex，CR超过10.8%之后断裂强度下降明显，CR达到25.4%时，断裂强度已降到5.5cN/dTex。其次，本论文还研究了AO-PAN纤维在不同实验条件下的吸附性能。结果显示，纤维对纯铀酰离子的吸附容量在48小时左右趋于平衡，随着CR从0升高到4.7%，吸附容量从0急剧增加到2.3mg/g，当CR超过10.8%时，吸附容量开始明显下降，到CR为46.3%时，吸附容量已降至1.2mg/g。在真实与模拟海水以及对其他共存离子的吸附实验中也得到了一致的趋势，吸附容量先随着CR及AOGD的增大而升高，但当CR超过10.8%，AOGD超过1.9mmol/g时，，吸附容量则开始明显下降。研究结果表明AO-PAN纤维对铀酰离子及竞争离子的吸附容量与CR及AOGD并不是呈线性的关系，升高CR及AOGD只有在较低时对纤维的吸附性能有利，过高则会影响材料吸附性能的表现。这是由于随着CR及AOGD的升高，相应地在纤维表面形成的凝胶层厚度也会增加，当凝胶层厚度超过1.4μm则会对AO-PAN纤维的吸附性能造成严重阻碍。综合分析后本论文得出结论，在AO-PAN纤维的制备过程中，单纯提升纤维的CR和AOGD并不可取，需要结合对纤维的机械强度及表面凝胶层厚度的控制，把握好这三者的平衡点，才能制备出拥有理想性能的吸附材料。
[Abstract]:As a result of the limited uranium resources on land , the research on uranium extraction has been initiated since the 1950s . It has been found that the adsorption method is the most promising method for uranium extraction . The amidoxime group is the key functional group which determines the adsorption property of amidoxime . The relationship between the adsorption performance of the material and the content of amidoxime group and the microscopic changes of the material in the process of preparation of amidoxime should be an important problem in the study of uranium extraction . It is believed that the content of amidoxime groups in the materials should be one of the main ways to improve the adsorption properties of the materials . However , the present paper holds that the relationship between CR and AOGD and the adsorption performance is studied . Therefore , the significance and purpose of this paper are to study the relationship between the CR and AOGD and the adsorption performance , and to explore the law , in order to provide a reference for further development of the adsorption material for uranium extraction . The effects of reaction time , temperature , hydroxylamine concentration , solvent ratio and pH value on the mechanical properties of AO - PAN fibers were studied . The results showed that the adsorption capacity of AO - PAN fibers increased with the increase of CR and AOGD , but the adsorption capacity increased with the increase of CR and AOGD . The results showed that the adsorption capacity of AO - PAN fibers increased with the increase of CR and AOGD . The results showed that the adsorption capacity of AO - PAN fibers was increased with the increase of CR and AOGD . After the comprehensive analysis , it is concluded that in the preparation of AO - PAN fiber , only the CR and AOGD of the fiber are not preferable , the mechanical strength of the fibers and the thickness of the surface gel layer are controlled , and the equilibrium points of the three are grasped , so that the adsorption material with desirable properties can be prepared .

【学位授予单位】：中国科学院研究生院（上海应用物理研究所）
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ136.2;TQ424

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