金属有机框架材料对水体中重金属离子去除性能及机理的研究进展

Research Progress on the Removal Performances and Mechanisms of Heavy Metal Ions from Aquatic Environments with MOFs

摘要:

工业化进程的加快导致全球环境污染日趋严峻，尤其是铬、砷、铅、汞、镉、锌、铜及镍等重金属污染极为显著。重金属在水体中多以离子态存在，难以生物降解，将对生态环境和人类健康构成巨大威胁，因此寻求经济、高效的重金属去除方法刻不容缓。水体中重金属去除的方法主要包括离子交换、混凝沉淀、氧化还原、吸附、膜过滤及电渗析等，其中吸附法具有成本低廉、操作简单和适应性强等诸多优点，被认为是去除水体中重金属的优选方法之一。金属有机框架材料（MOFs），因其比表面积大、孔隙率高、活性位点丰富、可调节性强及热/化学稳定性高等特性，被广泛应用于去除水体中的重金属。重点综述了MOFs及其复合材料对铬、砷、铅、汞、镉、锌、铜及镍重金属离子的去除性能，分析了MOFs初始浓度、重金属离子浓度、接触时间、pH 值、温度及干扰离子等因素对重金属去除效果的影响。同时，明确了MOFs去除重金属离子的机理。其主要作用机理为吸附、沉淀及氧化还原，其中吸附分为物理吸附和化学吸附，物理吸附主要包括静电引力、扩散作用和范德华力，化学吸附主要包括开放金属位点/配位作用、酸碱作用及氢键作用，而沉淀或者氧化还原伴随在吸附过程中。此外，对今后MOFs材料在重金属污染防治领域的研究方向及潜在应用进行了展望，以期为MOFs材料在环境污染修复领域的研究和应用提供理论基础。

Abstract:

The acceleration of industrialization has been leading to increasingly severe global environmental pollution， particularly in heavy metal pollutants such as chromium， arsenic， lead， mercury， cadmium， zinc， copper and nickel， etc. Removal methods for heavy metals from aquatic environments mainly include ion exchange， coagulation and sedimentation， oxidation-reduction， adsorption， membrane filtration， and electrodialysis. Among them， adsorption is considered one of the most promising methods for its advantages such as low cost， simple operation， and strong adaptability. Metal-organic framework materials （MOFs） are widely used for heavy metal removal due to their large surface area， high porosity， rich active sites， strong tunability， and excellent thermal/chemical stability. Therefore， this paper focuses on the removal performance of MOFs and their composite materials for eight typical heavy metal ions. It also analyzes the effects of factors such as initial MOFs concentration， heavy metal ion concentration， contacting time， pH value， temperature， and co-existing ions on the removal performances of heavy metals. Based on this， the main mechanisms of MOFs for removing heavy metal ions are explained by adsorption， precipitation， and oxidation-reduction， adsorption can be divided into physical adsorption and chemical adsorption. Physical adsorption mainly includes electrostatic attraction， diffusion， and van der waals forces， while chemical adsorption mainly includes open metal sites/coordination， acid-base interactions， and hydrogen bonding. Meanwhile， surface precipitation or redox reactions occur during the adsorption process. Additionally， this paper proposes the future research direction and potential applications of MOFs in the prevention and control of heavy metal， providing a theoretical basis for the research and application of MOFs in the field of environmental pollution remediation.