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Mechanisms for aqueous photolysis of adsorbed benzoate, oxalate, and succinate on iron oxyhydroxide (goethite) surfaces

Environmental Science and Technology

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Abstract

Photolysis of carboxylate anions adsorbed onto highly crystalline goethite (??-FeOOH) with 300-400-nm light produces Fe2+(aq) and ??OH from surface and solution redox reactions. The production of Fe2+(aq) and ??OH was studied in N2-purged and aerated aqueous suspensions, respectively, of goethite containing equimolar (10-3 M) concentrations of oxalate and benzoate (ob + g), succinate and benzoate (sb + g), benzoate alone (b + g), and goethite alone (g). The hydroxyl radical was measured by fluorescence analysis of salicylate formed in a reaction between benzoate and ??OH. Fe2+(aq) was determined colorimetrically. A proposed reaction mechanism includes the photoexcitation of Fe(III) surface complexes with OH-, HCO3-, and RCOO- ligands to form Fe2+(aq) and corresponding ligand radicals. Additional ??OH is made by the O2 oxidation of Fe2+(aq) (Haber-Weiss mechanism). Comparison of Fe2+(aq) and ??OH yields permitted an estimate of the relative importance of pathways leading to ??OH.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Mechanisms for aqueous photolysis of adsorbed benzoate, oxalate, and succinate on iron oxyhydroxide (goethite) surfaces
Series title:
Environmental Science and Technology
Volume
22
Issue:
9
Year Published:
1988
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
1090
Last page:
1097
Number of Pages:
8