Role of Ferrate(IV) and Ferrate(V) in Activating Ferrate(VI) by Calcium Sulfite for Enhanced Oxidation of Organic Contaminants

Although the Fe­(VI)–sulfite process has shown great potential for the rapid removal of organic contaminants, the major active oxidants (Fe­(IV)/Fe­(V) versus SO4 •–/•OH) involved in this process are still under debate. By employing sparingly soluble CaSO3 as a slow-releasing source of SO3 2–, this...

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Bibliographic Details
Published in:Environmental science & technology 2019-01, Vol.53 (2), p.894-902
Main Authors: Shao, Binbin, Dong, Hongyu, Sun, Bo, Guan, Xiaohong
Format: Article
Language:English
Subjects:
Anions
Antibiotics
Calcium
Contaminants
Contamination
Hydrogen peroxide
Iron
Organic contaminants
Oxidants
Oxidation
Oxidizing agents
Pesticides
Pollutant removal
Species
Sulfite
Water pollution
Water treatment
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Summary:Although the Fe­(VI)–sulfite process has shown great potential for the rapid removal of organic contaminants, the major active oxidants (Fe­(IV)/Fe­(V) versus SO4 •–/•OH) involved in this process are still under debate. By employing sparingly soluble CaSO3 as a slow-releasing source of SO3 2–, this study evaluated the oxidation performance of the Fe­(VI)–CaSO3 process and identified the active oxidants involved in this process. The process exhibited efficient oxidation of a variety of compounds, including antibiotics, pharmaceuticals, and pesticides, at rates that were 6.1–173.7-fold faster than those measured for Fe­(VI) alone, depending on pH, CaSO3 dosage, and the properties of organic contaminants. Many lines of evidence verified that neither SO4 •– nor •OH was the active species in the Fe­(VI)–CaSO3 process. The accelerating effect of CaSO3 was ascribed to the direct generation of Fe­(IV)/Fe­(V) species from the reaction of Fe­(VI) with soluble SO3 2– via one-electron steps as well as the indirect generation of Fe­(IV)/Fe­(V) species from the self-decay of Fe­(VI) and Fe­(VI) reaction with H2O2, which could be catalyzed by uncomplexed Fe­(III). Besides, the Fe­(VI)–CaSO3 process exhibited satisfactory removal of organic contaminants in real water, and inorganic anions showed negligible effects on organic contaminant decomposition in this process. Thus, the Fe­(VI)–CaSO3 process with Fe­(IV)/Fe­(V) as reactive oxidants may be a promising method for abating various micropollutants in water treatment.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.8b04990