梳型导向聚离子液体接枝印迹膜的构筑及其选择性分离稀土镥离子的行为机理研究

Since highly selective separation of single rare earth element is critical to the fine development and application of rare earth resources, intensive study into this separation field is in accordance with our national strategic needs. Herein we propose a novel synthesis strategy for a comb-like poly (ionic liquid) imprinted membrane on the selective separation of critical strategic rare earth element lutetium. First a novel dialkyl phosphorus based ionic liquid with polymerizable conjugated double bond is synthesized as functional monomer to fulfill the coordinated prepolymerization with lutetium ion in aqueous phase; then polyphenylene oxide is chosen as non-polar backbone polymer, together with the aqueous coordinated prepolymerization system serving as second monomer, the proposed comb-like poly (ionic liquid) grafted imprinted membrane could be obtained through RAFT controllable copolymerization and phase inversion. The membrane material would get fine islands-in-sea morphology and be applied in the selective recognition and separation of lutetium. The recognition mechanism, thermodynamics equilibrium rules and kinetics mass transfer model are discussed and deduced. And simulated actual leachate of rare earth ore, including lutetium ions, other co-existed rare earth ions and non-rare earth ions, will also be taken into consideration. According to the above researches, we hope to broaden the range of options for water-soluble and polar imprinting functional monomers, so that the application area of imprinting technique will be expanded and the fundamental separation research and technology for single high purity rare earth product will be solved. All these would provide our nation’s rare earth separation with a novel membrane strategy.

单一稀土元素的高效分离是稀土资源精细开发利用的关键，对其开展深入研究符合我国战略需求。本项目拟制备梳型导向聚离子液体印迹膜，并将其应用于分离关键战略稀土元素镥。以二烷基磷（膦）酸酯类离子液体作为功能单体，实现其与镥离子在水相中配位预聚；以聚苯醚为非极性主链，以水相预聚自组装体为接枝共聚第二单体，通过RAFT可控共聚并相转化成膜，构筑具有“海-岛”状相分离构型的梳型导向共聚物膜；将该膜材料应用于对镥离子的高效识别、吸附分离中，强化对镥离子识别机制、热力学平衡规律、动力学传质模型的理解，并模拟实际稀土矿浸出液中镥离子、伴生稀土离子与非稀土离子配分，进行小比例放大过程探索。通过本项目的研究，拓宽水溶性、极性印迹功能单体的选择范围，拓展印迹技术在水溶性、极性模板物质识别中的应用；为从源头上解决单一高纯稀土产品的分离、推进我国稀土分离技术进步提供一种新方法，解决我国稀土分离基础性研究工作的瓶颈问题。

相邻稀土离子间物理化学性质极其相似，且伴生共存于矿物中，导致相邻稀土元素间的分离十分困难。膜分离法高效绿色，但需强化选择分离性能。将离子印迹技术应用于构建稀土离子印迹膜，有望实现对相邻重稀土离子高效绿色分离。.1.利用对重稀土离子具有良好选择性的双功能型离子液体Cyphos IL 104，制备了PVDF- Cyphos IL 104聚合物杂化膜，研究其对相邻重稀土镱与镥的吸附分离行为与机理。通过衰FT-IR和XPS证实只有P=O和P-O基团参与了RE-Cyphos IL 104络合物的形成。SEM观察到该PIM具有拇指状不对称结构。水接触角的减小证明了离子液体的加入提高了亲水性。动态传输结果表明镥与镱的渗透系数分别是156和114.82μm s-1，对应的最初膜通量分别是90.17与65.61 μmol m-2 s-1，计算得到Yb(III)与Lu(III)的分离系数为1.37。.2.在上述 PIM膜中添加亲水性乙烯-乙烯醇共聚物（EVOH），提高基膜亲水性与后续水相印迹效率。将PVDF、EVOH与Cyanex 272通过相转化法制得PIM基膜。以钇离子为模板离子，衣康酸为印迹功能单体，N, N’-亚甲基双丙烯酰胺为交联剂，通过在水相中的氧化还原引发聚合，制得钇离子印迹膜（Y-IIMs）。通过FTIR、XPS及SEM等对Y-IIMs进行表征，P=O与P-O为主要参与RE-Cyanex 272络合物形成的基团。膜的孔道内壁和表面生长了一层印迹聚合物。Y-IIMs对钇的吸附量是非印迹膜的3倍，β(Y/Ho)和β(Y/Er)由未印迹的1.27和0.88提升至印迹后1.66和1.36，并对钇进行了优先渗透传输。βr(Y/Ho)和βr(Y/Er)分别为1.32和1.45。.3. 以多巴胺改性后的PVDF-Cyanex 272静电纺丝膜作为基膜，以钇离子为模板离子，通过溶胶凝胶表面印迹法制备了钇离子印迹静电纺丝膜。Cyanex 272加入以及亲水印迹聚合物的形成，改善了该膜材料亲水性。Y-IIEMs对钇离子吸附量是NIMs的7倍，且对Y(III)表现出优秀的吸附性能。该膜对钇进行优先传输，所获得β(Y/Ho)和β(Y/Er)由未印迹的1.24和0.85提升至印迹后的2.01和1.77，βr(Y/Ho)和βr(Y/Er)分别为1.83和2.08。