新型功能化石墨烯纳米带气凝胶的可控构筑及其对铀的吸附行为研究

Uranium is not only an important nuclear fuel, but also a potential radioactive pollutent. Therefore, separation and recovery of uranium from various uranium-containing aqueous systems are of great importance for sustainable development of nuclear energy and ecological security. Developing functional materials with high separation efficiency, good selectivity, excellent chemical and irradiation stability is very crucial to separation and recovery of uranium. Herein, the graphene nanoribbons will be used as matrix materials because of their adjustable structure and easy functionalization, stable and open graphene nanoribbons aerogels with three-dimensional network architecture will be constructed by means of hydrothermal in-situ assembly method. Then the speical groups such as phosphoryl, amidoxime and amide groups will be grafted onto the skeletons of graphene nanoribbons aerogels by ways of perfusion-evaporation-drying technique in order to synthesize several novel functionalized graphene nanoribbons aerogels with excellent selectivity to uranium and easy solid-liquid separation. Moreover, the effects of synthesis conditions on sorption properties and microstructures of functionalized graphene nanoribbons aerogels will be studied, and the relationship between structures and sorption properties will be explored. The sorption mechanism of uranium on the functionalized graphene nanoribbons aerogels will be disclosed at the molecular level by advanced spectroscopic analysis methods ( XPS and EXAFS etc.) and theoretical calculation. Additionally, functionalized graphene nanoribbons aerogels will be applied to separate uranium from simulated nuclear industrial efflunet and seawater. The results of this work will be expected to provide the fundamental and scientific basis for separating and concentrating uranium.

铀既是重要的核燃料，也是潜在的放射性污染物。从不同含铀水相介质中高效分离、富集铀，对实现核能可持续发展以及环境保护均具有十分重要的意义。本项目拟利用结构可调、易于功能化的石墨烯纳米带作为基质材料，采用水热原位组装法制备稳定、开放的具有三维网状结构的石墨烯纳米带气凝胶，并应用“灌注-蒸发-干燥”工艺将专属官能团接枝在石墨烯纳米带气凝胶的骨架上，以构筑出几种对铀选择性强、易于固液分离的新型功能化石墨烯纳米带气凝胶吸附分离材料。在此基础上，研究合成条件对功能化石墨烯纳米带气凝胶的微观结构和吸附性能的影响，探讨其吸附铀的构效关系；结合HRTEM、XPS，EXAFS等先进分析手段和理论计算在分子水平上探讨功能化石墨烯纳米带气凝胶吸附铀的作用机理；尝试开展功能化石墨烯纳米带气凝胶对模拟核工业流出物和模拟海水中吸附铀的探索研究。研究成果将为铀的分离和富集提供理论基础和科学依据。

石墨烯纳米带是宽度为几十纳米的石墨烯，比石墨烯具备更灵活可调的性质和更大的应用价值，兼具碳纳米管和石墨烯两者的优良性质。但呈粉末状的石墨烯纳米带作为吸附剂在实际应用中存在分离困难的问题，为解决纳米粉体吸附材料在水中的有效分离，将纳米材料气凝胶化是促进其实用化的方法之一。本项目利用水热原位组装法将石墨烯纳米带组装成石墨烯纳米带气凝胶，然后将磷酸基、偕胺肟基以及酰胺基聚合物沉积在石墨烯纳米带骨架的孔壁上，构筑出一系列功能化石墨烯纳米带气凝胶三维网状吸附材料，并将其应用于铀酰离子的吸附研究。本研究特别筛选出一种对铀具有高吸附容量和高选择性的聚偕胺肟/石墨烯纳米带气凝胶（PAO/GONRs-A）吸附分离材料，详细考察了其对铀的吸附行为。结果表明，PAO/GONRs-A为三维立体网状结构，具有很好的热稳定性；PAO/GONRs-A对U(VI)的吸附过程是受pH影响的，不受离子强度影响的，是一个快速、自发、吸热的准二级动力学过程；该吸附符合Langmuir模型，PAO/GONRs-A对铀的最大吸附量分别为527 mg g−1，经偕胺肟功能化后，PAO/GONRs-A对铀的吸附量大大提高；在包含铀在内的12种金属竞争离子存在的模拟核工业流出物样品中，PAO/GONRs-A对铀的吸附高达297.5 mg g−1，占总吸附量的65.1%，相对于GONRs提高了近4倍，选择性提高了约3倍；PAO/GONRs-A对铀的吸附是一个比较复杂的吸附过程，除涉及与羟基、羧基的络合过程外，铀酰离子还会与PAO/GONRs-A表面上的大量的含O和含N官能团形成稳定的络合物。该项目的研究成果将为铀分离富集提供理论基础和科学依据。