Department of Chemistry and Chemical Engineering , Inha University , Incheon 22212 , Republic of Korea.
ACS Appl Mater Interfaces. 2019 Mar 27;11(12):11488-11497. doi: 10.1021/acsami.9b00546. Epub 2019 Mar 15.
In order to meet the ever-increasing industrial demand for rare-earth elements (REEs), it is desirable to separate and recycle them at low concentrations from various sources including industrial and urban wastes. Here, we introduced phosphorus binding sites on the hydrophobic surface of a robust and high-surface area porous polymer backbone for environmentally benign and selective recovery of REEs via adsorption. For this purpose, two porous covalent organic polymer (COP) materials incorporated with in-built phosphite functionality (P-COP-1 and P-COP-2) were synthesized and applied for the adsorptive separation of Nd(III) ions from aqueous solution. A strategy to develop a series of P-COPs via a simple Friedel-Crafts reaction was introduced, and their application to the selective adsorption of REEs was explored for the first time. The newly synthesized P-COPs were amorphous and/or weakly crystalline and showed excellent chemical stability and large specific surface area with sufficient mesoporosity for enhanced diffusion of REE ions. P-COP-1 exhibited an exceptionally high Nd(III) adsorption capacity of 321.0 mg/g, corresponding to the stoichiometric ratio of P/Nd(III) = 1:0.7 and high selectivity of >86% over other competing transition and alkaline earth metal ions, whereas P-COP-2 gave a Nd(III) adsorption capacity of 175.6 mg/g at 25 °C and pH 5. Moreover, P-COP-1 showed a distribution coefficient value of 5.45 × 10 mL/g, which is superior to other benchmark adsorbent materials reported so far. Finally, the P-COPs were reusable for a minimum of 10 cycles without deterioration in adsorption capacities.
为了满足工业界对稀土元素（REEs）日益增长的需求，理想情况下是要从工业和城市废物等各种来源中以低浓度分离和回收这些元素。在这里，我们在坚固的高表面积多孔聚合物骨架的疏水性表面上引入了磷结合位点，通过吸附实现了 REEs 的环境友好和选择性回收。为此，我们合成了两种带有内置亚膦酸酯官能团的多孔共价有机聚合物（COP）材料（P-COP-1 和 P-COP-2），并将其用于从水溶液中吸附分离 Nd(III)离子。我们引入了一种通过简单的傅克反应开发一系列 P-COPs 的策略，并首次探索了其在选择性吸附 REEs 方面的应用。新合成的 P-COPs 为无定形和/或弱结晶，表现出极好的化学稳定性和大的比表面积，具有足够的中孔，有利于 REE 离子的扩散。P-COP-1 对 Nd(III)的吸附容量高达 321.0 mg/g，与磷/钕（III）的化学计量比为 1:0.7，对其他竞争过渡金属和碱土金属离子的选择性>86%，而 P-COP-2 在 25°C 和 pH 5 时的 Nd(III)吸附容量为 175.6 mg/g。此外，P-COP-1 的分配系数值为 5.45×10 mL/g，优于迄今为止报道的其他基准吸附剂材料。最后，P-COPs 至少可重复使用 10 次而不会降低吸附容量。
