Ni-MOFs对水中全氟烷基醚磺酸盐的吸附性能及机理

Adsorption performance and mechanisms of Ni-MOFs towards chlorinated polyfluoroalkyl ether sulfonic acid in aqueous phase

为有效去除水中的全氟烷基醚磺酸盐(F-53B),采用溶剂热法合成二维Ni-MOFs和三维Ni-MOFs材料。采用XRD、FTIR、SEM、N2吸/脱附实验和热重分析对材料的结构形貌和热稳定性进行了表征,采用动力学和热力学实验以及对比分析,考察了Ni-MOFs对水中F-53B的吸附性能,并进一步结合理论计算探究了可能的吸附机理。结果表明,2种材料均具有明显的晶型,其中Ni是以双齿配位模式与有机骨架进行结合,二维Ni-MOFs呈现分散片层结构,三维Ni-MOFs则呈现出块状结构,二维Ni-MOFs比三维Ni-MOFs具有更高的比表面积、孔隙率和热稳定性。2种材料对F-53B的吸附均符合准二级动力学方程和Freundlich等温方程,二维Ni-MOFs的吸附速率常数和吸附容量分别达到0.0024 g·(min·mg)^(−1)和451.2 mg·g^(−1),比三维Ni-MOFs分别高出20%和16%,吸附过程以非均质多层吸附为主,受共存阴离子的影响较小。对F-53B的吸附性能与2种材料的构效有关,活性吸附位点和限域作用决定了二维Ni-MOFs比三维Ni-MOFs更优的吸附特性,吸附过程主要受静电作用控制。以上研究结果表明二维Ni-MOFs对F-53B的吸附性能较好,具有良好的应用前景。

To effectively remove chlorinated polyfluoroalkyl ether sulfonic acid(F-53B)in aqueous phase,two metal-organic framework materials(2D Ni-MOFs and 3D Ni-MOFs)were prepared via solvothermal method.Multiple technologies,including X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM),N2 adsorption/desorption,and thermogravimetry(TG),were used to characterize the structure,morphology,and thermal stability of Ni-MOFs samples.The kinetic and thermodynamic experiments and comparative analysis were used to investigate the performance of Ni-MOFs towards of F-53B in aqueous phase.Moreover,the theoretical calculation was combined to further investigate the adsorption mechanism.Results showed that 2D and 3D Ni-MOFs were crystal materials,of which Ni bonded the organic framework with the bidentate complex form.2D Ni-MOFs presented a lamellar structure,and 3D Ni-MOFs exhibited a massive structure.2D Ni-MOFs had a higher specific surface area,porosity and thermal stability than those of 3D Ni-MOFs.The adsorption kinetics and isotherms of F-53B were in line with the pseudo-second-order model and Freundlich model,respectively.The adsorption rate constant and adsorption capacity of 2D Ni-MOFs reached 0.0024 g·(min·mg)^(−1)and 451.2 mg·g^(−1),respectively,which were 20%and 16%higher than those of 3D Ni-MOFs.Moreover,the adsorption process was dominated by the heterogeneous multilayer adsorption,and the co-existing anions had negligible impacts on the adsorption of F-53B on 2D Ni-MOFs.The adsorption performance of Ni-MOFs to F-53B was dependent on their structure-effect.The abundant active adsorption sites and confinement effect determined the better adsorption performance of 2D Ni-MOFs than 3D Ni-MOFs,and the adsorption process was mainly controlled by electrostatic interaction.The results of this study showed that 2D Ni-MOFs is an excellent adsorbent for F-53B and has a good application prospect.