多孔氧化石墨烯膜制备及其对铀的高效富集研究

In order to reduce the environmental pollution caused by fossil energy consuming, to push the development of nuclear energy is one of the most important steps in our country. However, the uranium reservation in our country is very limit. Extracting uranium from ocean may become an important way to obtain uranium resource in the future. The obvious size differences between uranium ion and main impure ions make the separation and accumulation of uranium from seawater possible through membrane separation method. Graphene and graphene oxide membranes are the new superstars rose in separation area, but both of them have advantages and drawbacks in real application. In present project, the advantages of both membranes are fully explored by preparing ultrathin porous graphene oxide (PGO) membrane through heavy ions irradiation of graphene oxide (GO) membrane, and then used for uranium accumulation from solutions. The nano-pores introduced in the GO membrane not only can create new vertical nano-passageways, but also can reduce the transmission distance of the ions, which will make the separation and accumulation of uranium more effectively with the cooperation of parallel nano-interlayers and vertical nano-pores in the PGO membrane. Moreover, the effects of membrane thickness, pore diameter, operation pressure and pore density will be systemically studied to further increase the uranium accumulation efficiency. The accumulation mechanism of uranium will also be deeply understood through the molecular dynamic simulation. All the above research work will give the basic data and move forward the engineered application of the economical PGO membrane in uranium extraction from seawater.

为减少消耗化石能源所造成的环境污染，积极推进和发展核能是我国一项重要举措；但核能发展的基础铀在我国储量有限，从海水中提取铀将成为未来人类获取铀资源的重要途径。由于海水中铀与其它主要杂质离子在尺寸上的显著差异，使得利用膜分离法实现铀的分离和富集成为可能。石墨烯和氧化石墨烯膜是分离研究领域的新星，但二者在实际应用中各有优缺点。本项目拟结合二者优势，在氧化石墨烯膜基础上，借助重离子辐照技术，制备超薄多孔氧化石墨烯（PGO）膜，开展溶液中铀的高效富集研究。氧化石墨烯膜中纳米孔的引入不仅增加了离子的传输途径，而且可缩短离子的传输距离，使得该膜可借助垂直孔道和层间传导协同作用实现铀和杂质离子选择性分离，将大幅提高铀的富集效率；此外，还可通过系统优化膜厚度、孔径大小、孔密度、操作压力等条件，进一步实现铀的高效富集；在此基础上，进行铀的富集机理研究，为价格低廉的PGO膜应用于海水铀富集的工程化提供依据。

本项目主要利用海水中铀和主要杂质离子在水合离子直径上的显著差异，，采用氧化石墨烯（GO）膜以膜分离方法开展海水中铀和主要杂质离子的分离及铀的预富集研究。为了达到上述研究目标，主要开展了以下研究工作，首先以甘氨酸（Gly）为交联剂，制备了GO-Gly膜，该膜克服氧化石墨烯（GO）膜在水溶液中易溶胀的缺陷，同时层间距满足海水中铀和主要杂质离子分离要求；以GO-Gly膜为分离膜进行了单一的铀和主要杂质离子（Na+，K+，Ca2+, Mg2+）离子的截留及模拟海水中铀的富集研究，发现该膜对铀的截留率达到~100 %且仅富集模拟海水中的铀；但是进一步研究发现， GO-Gly膜的层间距在实际海水酸度范围内不稳定，故以高分子聚丙烯酸（PAA）为交联剂制备GO-PAA膜。对膜的制备条件和厚度进行了优化，确定该膜在实际海水pH下层间距可长期保持稳定且铀截留率及水通量较高；此外，为了进一步提高GO-Gly，GO-PAA膜对铀的富集效率，分别采用重离子辐照和化学蚀刻的方法制备了多孔GO-Gly膜和GO-PAA膜，后期将以上述两个膜为基础，深入开展海水中铀的预富集研究。