The Fenton Reaction in Water Assisted by Picolinic Acid: Accelerated Iron Cycling and Co-generation of a Selective Fe-Based Oxidant

The Fenton reaction is limited by a narrow acidic pH range, the slow reduction of Fe­(III), and susceptibility of the nonselective hydroxyl radical (HO•) to scavenging by water constituents. Here, we employed the biodegradable chelating agent picolinic acid (PICA) to address these concerns. Compared...

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Bibliographic Details
Published in:Environmental science & technology 2021-06, Vol.55 (12), p.8299-8308
Main Authors: Yang, Zhichao, Shan, Chao, Pan, Bingcai, Pignatello, Joseph J
Format: Article
Language:English
Subjects:
2,4,6-Trichlorophenol
Acidic oxides
Atrazine
Autocatalysis
Biodegradability
Biodegradation
Chelating agents
Chelation
Cogeneration
Cycles
Herbicides
Hydrogen peroxide
Hydroxyl radicals
Iron
Iron constituents
Oxidants
Oxidation
Oxidizing agents
pH effects
Phenols
Picolinic acid
Reduction
Scavenging
Selectivity
Sulfamethazine
Treatment and Resource Recovery
Trichlorophenol
Trichlorophenols
Wastewater treatment
Water analysis
Water sampling
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Summary:The Fenton reaction is limited by a narrow acidic pH range, the slow reduction of Fe­(III), and susceptibility of the nonselective hydroxyl radical (HO•) to scavenging by water constituents. Here, we employed the biodegradable chelating agent picolinic acid (PICA) to address these concerns. Compared to the classical Fenton reaction at pH 3.0, PICA greatly accelerated the degradation of atrazine, sulfamethazine, and various substituted phenols at pH 5.0 in a reaction with autocatalytic characteristics. Although HO• served as the principal oxidant, a high-spin, end-on hydroperoxo intermediate, tentatively identified as PICA–FeIII–OOH, also exhibited reactivity toward several test compounds. Chloride release from the oxidation of 2,4,6-trichlorophenol and the positive slope of the Hammett correlation for a series of halogenated phenols were consistent with PICA–FeIII–OOH reacting as a nucleophilic oxidant. Compared to HO•, PICA–FeIII–OOH is less sensitive to potential scavengers in environmental water samples. Kinetic analysis reveals that PICA facilitates Fe­(III)/Fe­(II) transformation by accelerating Fe­(III) reduction by H2O2. Autocatalysis is ascribed to the buildup of Fe­(II) from the reduction of Fe­(III) by H2O2 as well as PICA oxidation products. PICA assistance in the Fenton reaction may be beneficial to wastewater treatment because it favors iron cycling, extends the pH range, and balances oxidation universality with selectivity.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.1c00230