Key Laboratory of Jiangxi Province for Persistent Pollutants Control and Resources Recycle, NanchangHangkong University
Department of Security and Protection, Aecc SouthIndustry Company Limited

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的分解,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)、电喷雾高分辨质谱(ESI-HRMS)分析发现,当 pH≤4,草酸根和铬酸根分别以 HC2O-4 和 HCrO-4 的形式存在时,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(HC2CrO-7 )。 在可见光的照射下,HC2CrO-7络合物草酸氧原子上的电子可以通过 HOMO-LUMO 跃迁的形式向铬酸根转移,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,确定Cr(Ⅵ)最终还原产物为低毒的 Cr(Ⅲ)-草酸络合物([Cr3+ -(C2O2-4 ) 3] 3-)。 根据检测到的反应产物,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) 技术提供理论依据。

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 chro⁃mate in natural waters. In this study, isothermal titration calorimetry (ITC), theoretical calculations,and electrospray ionization high resolution mass spectrometry ( ESI - HRMS) analysis revealed thatoxalic acid could complex with chromate to form a Cr(Ⅵ)-oxalate complex via an esterification processat pH≤4. The in situ generated HC2CrO7 complex was a visible-light-active species, and visible lightcould induce electron transfer from the oxalate unit to the Cr(Ⅵ) within the HC2CrO7 complex via aHOMO-LUMO electronic transition, resulting in Cr(Ⅵ) reduction. Subsequently, we verified the Cr(Ⅵ)reduction intermediates, and the hypotoxic Cr(Ⅲ) species [Cr3+-(C2O2-4 ) 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 oxalicacid.

国家自然科学基金资助项目(52360027)

关盈盈, 王浩, 葛小明, 等. 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[J]. 能源环境保护, 2024, 38(1): 109-118.

GUAN Yingying, WANG Hao, GE Xiaoming, et al. The coordination complex formed by oxalic acid and chromateand the mechanism for enhanced photoreduction of Cr(Ⅵ) under visible-light irradiation[J]. Energy Environ⁃mental Protection, 2024, 38(1): 109-118.