MOFs及其功能化改性材料对PFOA吸附的构效关系与作用机理研究

As a group of emerging persistent organic pollutants，perfluoroalkyl substances (PFASs) has aroused a growing public concern due to their widespread distribution and health hazards. Metal-organic frameworks (MOFs), a novel adsorbent with large specific surface area and excellent pore characteristics, has a great potential for the removal of PFASs in water. In this study, the adsorption mechanisms as well as the structure-adsorption correlations between different MOFs and perfluorooctanoic acid (PFOA), one of the most commonly detected PFASs in the environment, will be investigated. In addition, two modification strategies, including using different percentages of aminated organic ligands to synthesize MOFs and making different amine ligands grafted on coordinatively unsaturated metal centers of MOFs, to improve their adsorption capacity, will be explored. The differences of PFOA adsorption capacity by the modified MOFs using two approaches will be identified and explained. Furthermore, the coupling mechanisms among the amount of amino group grafted, MOFs structures, adsorption capacity and mechanisms will be established, to clarify the synergistic/antagonistic effect of amino group decoration. Furthermore, the effect of composed iron oxide nanoparticles on the adsorption capacity of amino MOFs for PFOA will be studied to explore the magnetic separation of the adsorbent. Finally, effective elution methods of PFOA will be studied for the regeneration of functional MOFs. The results in this study will provide fundamental understanding for the MOFs applications in PFASs remediation.

作为新兴持久性有机污染物，全氟化合物(PFASs)的广泛分布和健康危害已引起公众日益关注。本项目拟以水体中典型PFASs种类全氟辛酸(PFOA)为目标污染物，研究新型吸附剂金属-有机骨架材料(MOFs)对PFOA的吸附性能与构效关系，探索吸附作用机制；为进一步提高吸附性能，将分别采用胺基结合MOFs材料不同比例的有机配体、多种胺类物质嫁接MOFs材料金属离子两种基团修饰策略进行功能化改性，解析不同修饰策略导致MOFs材料吸附PFOA性能的差异及原因，探索胺基修饰量与MOFs材料功能结构、吸附性能和作用机理的关联耦合机制，阐明胺基修饰的协同/拮抗作用机理；研究氧化铁纳米颗粒负载对胺基化MOFs材料吸附性能的影响机制，探索材料的磁性分离与回收，研究经济高效的PFOA洗脱方法，评估功能化MOFs材料的再生与循环利用性能，从而为地下水和地表水中PFASs的污染修复技术提供科研借鉴与技术支持。

本项目以全氟/多氟化合物（PFASs）为目标污染物，以研发金属-有机骨架（MOFs）及其功能化改性材料为核心，借助宏观吸附实验以及晶体结构、官能团、比表面积、元素能谱等微观表征技术，取得以下创新成果：1）从升温程序、滤洗除杂两方面改进MOFs制备活化方法，研发3种柔性菱形孔道材料MIL-53(Al)、MIL-53(Fe)、MIL-53(Cr)和2种刚性足球状孔笼材料MIL-101(Fe)、MIL-101(Cr)，进一步筛选出高吸附性能材料MIL-101(Cr)。2）液膜扩散是MIL-101(Cr)吸附PFASs的关键限速步骤。具有磺酸基团、较短碳链、支链和醚键等分子特征的PFASs吸附量较高，但碳链上存在部分H原子的PFASs吸附量较低。非专性吸附为关键机制，主要体现在PFASs的C-F、C-O与MIL-101(Cr)有机配体间的静电及氢键作用；PFASs的羧基和磺酸基也可与MIL-101(Cr)中心铬离子形成络合物。PFASs单个C（S）基团平均电负性与MIL-101(Cr)吸附量间符合逻辑斯蒂方程。3）通过热合成法分别将乙二胺（ED）、三(2-氨基乙基)胺（TEMA）修饰到MIL-101(Cr)，可增加作用位点与静电吸附，大幅提高PFASs吸附量；其中MIL-101(Cr)-TEMA对PFOA、PFOS吸附量高达2407μmol/g、3773μmol/g。4）0.8mg/L MIL-101(Cr)对总浓度为114μg/L PFASs去除率超过75%。针对PFASs同分异构体，MIL-101(Cr)对支链构型吸附去除率高于直链构型。基于离子竞争吸附和疏水作用研发了高效洗脱剂， MIL-101(Cr)循环利用3次后仍可达初始吸附量76.8%。本项目探究了MOFs及其功能化改性材料对PFASs吸附的性能、机理与构效关系，为高效净化材料和快速监测探针研发提供理论基础与技术支撑。