纳米金刚石的微波法快速合成、表面修饰及铀吸附性能研究

Nuclear energy is considered one of the most promising energies to solve the problem of fossil energy exhaustion. It is also regarded as an important energy in China's mid and long-term development plan. However, the uranium resources are not rich in China. Therefore, it is very important to develop efficient, stable and environmental-friendly materials with high affinity and efficiency for separation of uranium to ensure the sustainable development of nuclear energy in future. In this project, a groundbreaking microwave synthetic method will be employed to prepare nanodiamonds with adjustable morphology, dimension and surface structure. Biomass materials that widely distribute in nature are used as carbon sources and the produced nanodiamonds will serve as matrix materials of solid-phase extractant. On the other hand, the ligands, including macrocycles and molecular tweezers, that can extract uranium with high selectivity and coordinate with uranium stably will be selected and synthesized by means of computer simulation and calculation, along with the experimental methods, and the well-selected ligands will be practiced to surface modification of the nanodiamonds. The thus-formed solid-phase extractants can give full play to the advantages of both matrix materials and the ligands on their surfaces, and combine them together well. This project will research detailedly on relation between material structure and adsorption performance and reveal preliminarily the design rules of selective ligands for uranium, and develop promising uranium extractant from uranium-containing water, including effluent generated during spent fuel reprocessing, radioactive waste water and sea water, etc. This research will provide important theoretical basis and reliable reference data for separation and enrichment of uranium resources from related water.

核能被认为是解决化石能源枯竭问题最有希望的能源形式之一，我国中长期发展规划也将核能列为重点发展能源。然而我国铀资源储量并不丰富，因此开发高效、稳定、环保的超亲铀高效分离材料对保障未来核能的持续发展至关重要。本项目以取材广泛的生物质材料为碳源，开创性地采用微波法制备形貌、尺度、表面结构等性质可调的纳米金刚石，并以此作为固相萃取剂的基质材料。另一方面，通过计算机模拟辅助设计与实验手段相结合的方法，筛选及合成对铀具有高选择性和配位稳定性的理想的大环和分子钳配体，用于纳米金刚石的表面功能化修饰。由此得到的固相萃取剂能够将所选基质材料和表面修饰配体有机结合以充分发挥两者的优良特性。本项目将详细研究材料结构与吸附性能间的关系，初步揭示铀选择性配体的设计规律，研制有应用前景的超亲铀萃取吸附材料，为从乏燃料后处理料液、放射性废水和海水等相关水体中分离富集铀资源提供重要的理论依据和可靠的参考数据。

放射性核素分离技术是乏燃料后处理及核能发展其他相关领域的核心技术之一，它所涉及的分离材料则是核心中的核心。其中关键核素铀的分离和回收技术一直是研究人员关注的重点，该技术的优化和改进必将为后期废物的处理和处置带来实质性的便利和可观的经济效益。本项目在微波辐照法制备纳米金刚石的基础上，采用纳米金刚石作为固相萃取剂的基质材料，同时结合近期材料科学研究的前沿，选择并制备石墨烯、共价及超分子有机框架等基质材料，通过多种功能化修饰改性方法，将具有不同组成和结构特性的亲铀性功能配体接枝修饰到基质表面，先后设计和制备了多种类型的固相萃取材料。通过全面、深入和细致的分析表征，详细考察了产物的结构特性及其在水溶液中对铀的萃取性能和相关影响因素，研究了吸附过程的动力学、热力学特性和吸附模式。此外，本项目还考察了制备材料在含有十余种核素离子的模拟核工业流出物体系中对铀的选择性吸附行为，探索了吸附机制，得到了对关键核素铀具有高选择性分离能力、有应用潜力的固相萃取剂材料。另一方面，本项目采用密度泛函理论结合实验手段系统地研究了制备材料的活性配位基团与铀酰离子相互作用过程和作用机理，考察了该过程热力学函数的改变以及相对应的微观配位结构的变化，首次提出了固相萃取剂与铀酰离子的配体交换机理，并基于该配体交换机理建立了适用于固-液萃取的位点吸附理论模型，该理论模型大大简化了之前研究中采用的对不同模型进行复杂的实验数据拟合的方法，具有重要的理论和实用意义，有望广泛应用于金属离子固-液萃取分离领域。本项目研究结果将深化我们对固相萃取材料高效分离铀的本质的认识，为在理论指导下设计与制备更加高效、适用的固相萃取剂提供切实可行的策略和可选途径。