草酸与铬酸根形成配位络合物强化可见光还原六价铬的机理研究  

The coordination complex formed by oxalic acid and chromate andthe mechanism for enhanced photoreduction of Cr(Ⅵ)undervisible-light irradiation

作　　者：关盈盈 王浩 葛小明 邓力恺 邓斌 穆毅 邹建平[1] GUAN Yingying;WANG Hao;GE Xiaoming;DENG Likai;DENG Bin;MU Yi;ZOU Jianping(Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle,Nanchang Hangkong University,Nanchang 630069,China;Department of Security and Protection,Aecc South Industry Company Limited,Zhuzhou 412002,China)

机构地区：[1]南昌航空大学江西省持久性污染物控制与资源化重点实验室,江西南昌630069 [2]中国航发南方工业有限公司安全保障部环境保护室,湖南株洲412002

出　　处：《能源环境保护》2024年第1期109-118,共10页Energy Environmental Protection

基　　金：国家自然科学基金资助项目(52360027)。

摘　　要：草酸是自然水体中广泛存在的一种小分子羧酸,主要来源于植物的根系分泌和有机质分解,对自然水体中Cr(Ⅵ)的还原有重要的影响。本研究通过等温滴定量热法(ITC)、电喷雾分辨质谱(ESI-HRMS)分析发现,当pH≤4,草酸根和铬酸根分别以HC2O_4^(-)和HCrO_(4)^(-)的形式存时,可以通过脱水缩合的方式形成具有可见光活性的草酸-铬酸配位络合物(HC_(2)CrO_(7)^(-))。在可光的照射下,HC_(2)CrO_(7)^(-)络合物草酸氧原子上的电子可以通过HOMO-LUMO跃迁的形式向铬酸转移,实现Cr(Ⅵ)的还原。借助电喷雾高分辨质谱检测了Cr(Ⅵ)还原过程中的中间产物,确Cr(Ⅵ)最终还原产物为低毒的Cr(Ⅲ)-草酸络合物([Cr^(3+)-(C_(2)O_4^(2-))_3]^(3-))。根据检测到的反产物,绘制了草酸可见光还原Cr(Ⅵ)的反应路径。本研究将为利用草酸高效光还原Cr(Ⅵ)术提供理论依据。Oxalic acid,which mainly originates from root exudation and plant residue decomposition,is one of the most widely existiug carboxylic acids,and has a dramatic impact on the reduction of chromate in natural waters.In this study,isothermal titration calorimetry(ITC),theoretical calculations,and electrospray ionization high resolution mass spectrometry(ESI-HRMS)analysis revealed that oxalic acid could complex with chromate to form a Cr(Ⅵ)-oxalate complex via an esterification process at pH≤4.The in situ generated HC_(2)CrO_(7)^(-)complex was a visible-light-active species,and visible light could induce electron transfer from the oxalate unit to the Cr(Ⅵ)within the HC_(2)CrO_(7)^(-)complex via a HOMO-LUMO electronic transition,resulting in Cr(Ⅵ)reduction.Subsequently,we verified the Cr(Ⅵ)reduction intermediates,and the hypotoxic Cr(Ⅲ)species[Cr^(3+)-(C_(2)O_(4)^(2-))3]^(3-)was the final product.Finally,the pathway of Cr(Ⅵ)reduction by oxalic acid under visible-light irradiation was proposed.This study will provide a theoretical basis for efficient photoreduction of Cr(Ⅵ)pollution using oxalic acid.

关 键 词：草酸 六价铬 光还原 重金属 

分 类 号：X703[环境科学与工程—环境工程]