竞争配位诱导分级孔金属有机骨架纳米吸附剂对稀土离子的吸附与分离

Adsorption and separation of rare earth ions by competitive coordination-induced hierarchical porous metal-organic frameworks

针对相邻稀土离子镨Pr、钕Nd、钐Sm的高效吸附与分离,采用溶剂热法,通过将月桂酸作为竞争配位剂,制备具有分级孔结构的多孔金属有机框架纳米吸附剂,提高了对稀土离子的吸附量与选择性。通过红外光谱、氮气吸脱附曲线、X射线衍射、扫描电镜等表征手段证明了所合成的MOF-5的化学组成、晶体结构以及分级孔结构。通过调控不同反应时间,制备的分级孔MOF-5表面被长度约0.1μm左右的棒状晶粒覆盖,整体呈边长1μm左右的立方体结构,并具有最佳的微孔与大孔比例,平均孔径16.46 nm。对镨、钕与钐的平衡吸附量分别为84.82 mg/g、153.88 mg/g、228.34 mg/g。从动力学吸附平衡数据计算分离系数分别为β(Sm/Nd)=1.47,β(Nd/Pr)=1.83。

Aiming at the efficient adsorption and separation of adjacent co-existed rare earth ions praseodymium(Pr),neodymium(Nd)and samarium(Sm),solvothermal method to construct a novel hierarchical MOF-5 adsorbent were applied using lauric acid as a competitive coordination agent.The chemical compositions,crystalline structure and hierarchical pore structures of the synthesized MOF-5 were demonstrated by infrared spectroscopy,nitrogen absorption and desorption curves,X-ray diffraction and scanning electron microscopy.By adjusting the solvothermal reaction time and lauric acid’s addition amount,the surface of the as-prepared hierarchical MOF-5 could be covered by a rod-like grain with average length of about 0.1μm,and the whole MOF-5 crystals were cubes with a side length of about 1μm,and the average pore size was around 16.46 nm.The equilibrium adsorption amounts of Pr,Nd and Sm were 84.82 mg/g,153.88 mg/g and 228.34 mg/g,respectively.The separation coefficients of Sm/Nd and Nd/Pr calculated from the kinetics adsorption equilibrium data were 1.47 and 1.83,respectively.