碳点复合材料的制备及其对铀的分离去除性能研究

Efficient separation and removal of uranium are of great significance for the energy structure and environmental protection in China. Among the common uranium separation methods, adsorption stands out due to many advantages. While, as the dominant materials, the adsorbents are still facing challenges to increase the adsorption capacity. In this project, the photocatalysis assisted adsorption strategy is proposed for the first time by using the photocatalysis methodology to reduce the U(VI) of which adsorbed on the material surface. Thus, the adsorption equilibrium will be overcome and the adsorption capacity will be increased. The carbon dot composite materials with promising adsorption and photocatalytic properties will be employed for the high-efficiency separation of uranium in the aqueous phase. Efforts will be devoted to preparing the carbon dots with distinct properties by modifying the raw materials and methods, to establishing and optimizing the complex methods between carbon dots and base materials. Influences of the composite materials on the adsorption behavior of uranium will be discussed and the adsorption mechanism will be determined. Meanwhile, efforts will be applied to investigating the photocatalytic property of carbon dot composites for uranium. The effects of the carbon dots on the photocatalytic ability will be analyzed and the mechanism will be explored, thus realizing the reduction of uranium, improving the adsorption capacity. This project is dedicated to develop new methods for preparing of carbon dot composites, to provide novel materials and to offer scientific insights for the adsorption and photocatalytic reduction of uranium.

铀的高效分离和去除对我国能源结构和环境保护均具有重要意义。在分离去除铀的常用方法中，吸附法脱颖而出。其中扮演核心角色的吸附剂仍面临需提高吸附容量的挑战。为此，本项目首次提出光催化辅助的吸附策略，利用光催化对吸附的铀酰离子进行还原，打破吸附平衡，提高吸附容量。项目将结合碳点复合材料的吸附性质和光催化性质实现对铀的高效分离去除。通过筛选不同原料和方法制备性质各异的碳点，建立并优化碳点与基底材料的复合方式，制备碳点复合材料。讨论复合材料对铀吸附性能的影响因素，阐明吸附机理。研究碳点复合材料对铀的光催化性能，分析碳点性质对光催化效果的影响，探究光催化机理，进一步提高复合材料对铀酰离子的吸附容量。本项目预期将为碳点复合材料的制备提供新方法，为铀的高效吸附和光催化还原提供新材料，为研究复合材料对铀酰离子的吸附机理和光催化还原机理提供科学依据。

研究铀的高效分离和去除的材料和技术对我国能源战略和环境保护均具有重要意义。本课题提出利用碳点的吸附和光催化性质，实现对溶液中铀酰离子的固化，发展一种光催化辅助提铀的新方法。我们首先合成了7种基于碳点的氮化碳复合材料，发现碳点的引入可以提高氮化碳的光电流密度，降低界面电荷转移阻抗，缩小带隙。优化并筛选出一种对铀具有高效光催化性能的材料，该材料在空气中能够光催化铀酰离子生成水丝铀矿，对铀的不饱和去除容量高达1690mg/g。接着合成了具有黄色荧光的碳点/聚氨酯的复合材料，该材料在高效除铀的同时能够实现固液快速分离，且生成的水丝铀矿能够自动脱落，实现活性位点的再生，具有优异的循环使用性能。此外，我们还深入研究了无外加催化剂时，利用铀酰离子的光化学性质完成对溶液中铀的固化提取的机理。实验发现在空气中，铀酰离子受光照激发后可以与甲醇等反应生成过氧化氢，而后再与局部高浓度的过氧化氢结合生成水丝铀矿。最后合成了石墨烯气凝胶、改性氮化碳等新型催化剂，用于溶液中铀酰离子的高效光催化去除。且合成的改性氮化碳能够在太阳光下固化模拟海水中的铀酰离子，初步实现了光催化辅助海水提铀的设想。本课题的完成有希望用于溶液中铀酰离子的光催化分离和去除，为该领域提供了新材料、新技术和新机理，为光催化剂的设计和合成提供了新思路。