The coordination complex formed by oxalic acid and chromate and the mechanism for enhanced photoreduction of Cr(Ⅵ)under visible-light irradiation
GUAN Yingying
WANG Hao
GE Xiaoming
DENG Likai
DENG Bin
MU Yi
ZOU Jianping
Abstract：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 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 HC2CrO-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 HC2CrO7-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[Cr3+-(C2O42-)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.
Keywords：Oxalic acidCr(Ⅵ)PhotoreductionHeavy metal
Publication Date：2024-02-28
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：10( 109-118 )