氧化石墨烯滤膜中含氧基团和离子的分布及其对离子筛选的影响

Graphene oxide membranes—partially oxidized, stacked sheets of graphene—can provide ultrathin, high-flux and energy-efficient membranes for precise ionic and molecular sieving in aqueous solution. Ions have strong interaction on oxygen-contained groups and aromatic rings of membranes soaked in salt solution. Furthermore, swelling of the membranes will be caused when immersed in aqueous solution. We have made a step in the study of ion sieving in graphene oxide membranes via cationic control of interlayer spacing. However, a series of basic scientific issues are still unclear, such as, the understanding of the interaction between oxygen-contained groups and ions, relationship between oxygen-contained groups and water channel, competition of adsorption sites of different cations in the membranes during ion sieving, et al. Herein, grapheme oxide membranes with different oxygen content and oxygen groups (epoxy, hydroxy, carboxyl) will be prepared, and analysis with high-precision experimental investigations in Shanghai synchrotron radiation facility (SSRF) together with theory simulation. We will study the general law of how the interaction between oxygen-contained groups/aromatic ring structures in membrane and the ions and water molecular affect the properties of graphene oxide membrane, such as, relationship between distribution of adsorption ions and oxygen-contained groups with different type (epoxy, hydroxyl or carboxyl group), distribution and content, respectively. And study the competitive relationship between different ions and the oxygen-contained group/aromatic ring on the surface of membranes in mixed salt solution system. Our study will provide mechanism analysis and theoretical basis for the application of water treatment in graphene oxide membranes.

层状堆叠的氧化石墨烯具有超薄、高流量、节能等特点，可实现溶液中精确的离子和分子筛选。在盐溶液渗透时，离子对膜内含氧基团和芳环结构有很强的相互作用；同时，渗透的水分子还会产生膜的溶胀。虽然我们利用水合离子-π相互作用对氧化石墨烯膜层间距进行精确控制的研究取得重要进展，但是对于膜内含氧基团/离子的分布及相互作用，膜内基团分布和水通道的关系，膜内不同离子对吸附位点的竞争等这些关键的基本科学问题仍然不清楚。本项目中我们将制备不同含氧量及含氧基团（环氧、羟基、羧基）的氧化石墨烯膜，重点结合上海光源的同步辐射实验及理论计算，研究石墨烯膜中离子与含氧基团和芳香环结构的相互作用及对膜结构和性质影响的一般规律；混盐体系下，不同离子之间在含氧基团/芳环表面的竞争关系及其对滤膜筛选性能的影响等。该项目将为氧化石墨烯膜在实际水处理应用提供机制分析和理论基础。

本项目运用同步辐射装置、配合常规表征方法，并且应用基础量子力学计算、经典分子动力学模拟验证相结合的方法，实验制备了不同含氧量和含氧基团的氧化石墨烯膜，研究和分析了不同离子对氧化石墨烯膜内片层间距离、内部通道大小等对盐离子的去除率等性质的影响。系统探析了含氧基团协同的水合离子-π相互作用的机制；基于高价态金属离子水合结构在氧化石墨烯膜受限空间内的物理机制的理解，提出优化氧化石墨烯膜的制备过程的方法。制备得到的氧化石墨烯膜在对高价态离子截留时，保持了非常高的高价态离子截留率（为99.9 ± 0.1%），同时水通量可达75 ± 2 L m−2 h−1 bar−1，超越所有现有报道的传统的纳滤膜以及其他先进的二维膜在处理高价态离子时的水渗透性能和稳定性，突破了此前方法得到的氧化石墨烯膜在离子截留率和选择性的瓶颈。相关系列研究工作，发表SCI论文17篇，其中一区SCI论文12篇；授权国家发明专利2项。