摘要/Abstract

采用联苯为建筑基元，合成了价格低廉、操作简便、易于工业化的多孔芳香骨架材料PAF-45.通过后修饰方法，制备了带有磷酸基团的多孔芳香材料（PAF-45-PG）.通过FTIR（傅里叶变换红外光谱），TGA（热重分析），PXRD（多晶粉末X射线衍射），SEM（扫描电子显微镜），TEM（透射电子显微镜）以及N₂吸附实验，对PAF-45-PG的结构及孔道性质进行了系统的表征.由于骨架中引入了磷酸基团，PAF-45-PG具有优良的铀离子吸附性能，在pH=6的条件下可以达到100 mg·g^-1.另外，该材料成本低廉，具有可观的工业化前景，为多孔材料在能源方面的应用提供了广阔前景.
关键词: 多孔芳香骨架, 磷酸基, 肖尔反应, 铀离子提取, 工业化
As a clean, safe, efficient, and economical energy, nuclear energy plays an irreplaceable role in the resource sector. However, uranium deposits on land will run out in the coming decades. The uranium content in seawater is huge but its concentration is as low as~3 ppb. So it is an urgent problem to design and synthesize adsorbent materials with high extraction efficiency. In this paper, taking the actual industrialization as the direction, we adopted biphenyl as the building block and synthesize the porous aromatic framework material (PAF-45) in a low price. Then porous aromatic framework material (PAF-45-PG) with phosphoric acid groups was prepared through a post-modification procedure. The structure and pore characteristics of the compound were investigated by FTIR, TGA, PXRD, SEM, TEM and N₂ adsorption experiments. FTIR spectrum indicates that the emerging vibrational peaks at 900~1250 cm^-1 can be ascribed to the successful decoration of phosphate groups in PAF-45-PG compared with pure PAF-45. Powder X-ray diffraction shows that PAF-45 and PAF-45-PG are amorphous. And transmission electron microscope (TEM) images also agree with the conclusion of PXRD that PAF materials possess disordered structure. Moreover, there is no significant weight loss before 400℃ demonstrated by thermogravimetric analysis, which indicates the high thermal stability of two PAF resultants. The porosity of PAF networks was characterized by measuring the N₂ adsorption isotherm at 77 K. Calculated by Brunauer-Emmett-Teller (BET) adsorption model, the specific surface area of PAF-45-PG is 426 m²·g^-1, which is lower than that of pure PAF-45 (828 m²·g^-1). This reduction of surface area is attributed to the introduction of functional groups which increase the weight per constitutional unit and occupy the space in the porous structure. After that, we tested the UO₂²⁺ ion adsorption of PAFs in simulated seawater. The equilibrium adsorption capacity of PAF-45-PG increases with the increase of uranium concentration, and reaches the maximum value (101 mg·g^-1) at about 8 ppm. Because the maximum capacity of PAF-45 is 5.9 mg·g^-1, this result indicates that the adsorption of uranium ion in PAF-45-PG is mainly caused by the post-modified phosphate functional group on its pore surface. Due to the low cost and simple preparation process, the material (PAF-45-PG) has a great industrial prospect.
Key words: porous aromatic frameworks, phosphate group, Scholl reaction, uranium extraction, industrialization


PDF全文下载地址:

点我下载PDF