Mechanistic study of Fe(III) chelate reduction in a neutral electro-Fenton process

[Display omitted] •Reduction mechanisms of Fe(III) chelates through electron and atomic H* were investigated.•Electron reduction was highly efficient for the [Fe(III)-EDTA]− and [Fe(III)-EDDS]− chelates.•[Fe(III)-HA]3+ chelate was reduced more readily by the atomic H* than electron.•Phthalocyanine h...

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Published in:Applied catalysis. B, Environmental Environmental, 2020-12, Vol.278, p.119347, Article 119347
Main Authors: Liu, Xiao-Cheng, He, Chuan-Shu, Shen, Zi-Yang, Li, Wen-Qiang, Chen, Ning, Song, Jun-Sheng, Zhou, Xiao-Guo, Mu, Yang
Format: Article
Language:English
Subjects:
Atomic H
Chelates
Chelation
Density functional theory
DFT calculations
Electro-Fenton
Electron
Electrons
Environmental degradation
Ethylenediaminetetraacetic acids
Fe(III) chelate reduction
Iron
Molecular orbitals
Pollutants
Reduction
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Summary:[Display omitted] •Reduction mechanisms of Fe(III) chelates through electron and atomic H* were investigated.•Electron reduction was highly efficient for the [Fe(III)-EDTA]− and [Fe(III)-EDDS]− chelates.•[Fe(III)-HA]3+ chelate was reduced more readily by the atomic H* than electron.•Phthalocyanine had an insignificant effect on pollutant degradation due to low chelate ability. Fe(III) chelate reduction is of great importance in the homogeneous neutral electro-Fenton (EF) process, but its reduction mechanisms with different reductive species remain unclear. In this study, the reduction mechanisms of several typical Fe(III) chelates through electron and atomic H* were investigated using experiments and density functional theory calculations. The results indicated that the electron reduction efficiencies for [Fe(III)-EDTA]− and [Fe(III)-EDDS]− chelates were 16.23 and 8.31 times higher compared to [Fe(H2O)6]3+, which was featured by low ELUMO-HOMO and concentrated LUMO distribution around Fe atom. In contrast, the atomic H* reduction efficiency for [Fe(III)-HA]3+ chelate was 10 times higher than that of electron, attributed to high chelation ability of HA and negative energy barrier of [Fe(III)-HA]3+ reduction in the atomic H*-dominated system. Additionally, phthalocyanine (Pc) had insignificant effect on pollutant degradation efficiency in the neutral EF systems due to the lower chelate ability of Pc with Fe(III) compared to H2O.
ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2020.119347