典型全氟烷基酸的光/电催化降解:性能提升策略与反应机制

Photocatalytic and electrocatalytic degradation of typical perfluoroalkyl acids:Performance improvement strategies and reaction mechanisms

全氟烷基酸(perfluoroalkyl acids,PFAAs)在全球水体中普遍存在,且对生物体和人体均具有潜在毒害作用,是近年来被广泛关注的主要污染物之一.水环境中PFAAs的去除和降解是降低其生态健康风险的重要手段,也是目前研究的焦点之一.PFAAs分子中所有C—H键均被C—F键取代,特殊的结构使PFAAs具有极高的化学稳定性,常规的氧化技术难以实现水环境中PFAAs的有效降解.光催化氧化和电催化氧化是目前处理难降解有机污染物的两种主要高级氧化技术,也是研究水环境中PFAAs降解去除的主流关键技术.以全氟辛基羧酸(perfluorooctanoic acid,PFOA)和全氟辛基磺酸(perfluorooctane sulfonates,PFOS)为研究PFAAs降解的两类典型代表,本文综述了近年来光催化氧化和电催化氧化两种技术在水相PFOA和PFOS降解研究的文献报道,对提高PFAAs降解效率所采用的主要技术改进策略及其背后的理论机制进行了梳理和总结.基于提高催化反应活性物质产率,增加活性反应位点和反应物传质效率以及提高反应体系稳定性等优化策略,对光催化中催化剂和电催化中电极材料的优选,通过元素掺杂、异质结构筑、金属沉积、材料复合、形貌调控等对材料进行特定功能化改性,以及向反应体系添加氧化物种前驱体、多技术耦合等协同改进方法,两类PFAAs的氧化降解效率显著提高.光/电催化氧化对水中PFAAs的去除率、脱氟率和矿化率(中位值)分别达到91%和98%、38%和76%、65%和81%,展现了这两种高级氧化技术在PFAAs降解中优越的性能和应用前景.结合两种高级氧化技术进展,展望其在PFAAs降解研究的发展方向,以期为今后PFAAs的污染控制技术研究提供有益参考.

Perfluorinated alkyl acids(PFAAs),a group of widely concerned pollutants in recent years,are widespread in water bodies around the world and are potentially toxic to both organisms and humans.The degradation and removal of PFAAs in aqueous environment are crucial means to reduce their ecological and health risks,and are also focuses of current research.PFAAs show extremely chemical stability due to all C—H bonds being replaced by C—F bonds,which makes it difficult to achieve effective degradation of PFAAs by conventional oxidation techniques.Photocatalytic oxidation and electrocatalytic oxidation are two main advanced oxidation techniques for the treatment of refractory organic pollutants and already become the key techniques for the degradation and removal researches of PFAAs in the aqueous environment.With perfluorooctanoic acid(PFOA)and perfluorooctane sulfonates(PFOS)been selected as the two typical representatives,we reviewed the literature reports on the degradation of PFAAs in the aqueous phase by photocatalytic oxidation and electrocatalytic oxidation in recent years.And the main technical improvement strategies and the underlying theoretical mechanism to improve the degradation efficiency were summarized.The main optimization strategies adopted in literature works including improving the yield of active groups in the catalytic reaction,increasing the active reaction sites and mass transfer efficiency of reactants,and improving the stability of the reaction system.Specific functional modifications such as element doping,heterostructure construction,metal deposition,material composition and morphology control,were carried out to optimize the catalysts in photocatalysis and the electrode in electrocatalysis.Several synergistic methods such as adjunction of active oxide precursors and multi-technology coupling were also applied to accomplishing significant improvements of oxidation degradation efficiency of the two types of PFAAs.The removal rate,defluorination rate,and mineralization rate(median)of PFOA and PFOS in water by photocatalytic/electrocatalytic oxidation reached 91% and 98%,38% and 76%,and 65% and 81%,respectively,demonstrating the superior performance and application prospects of these two advanced oxidation techniques in the degradation of PFAAs.Finally,based on the progress in the two advanced oxidation technologies,development directions of PFAAs degradation research were prospected.We hope this review will help in the pollution control researches of PFAAs in future.