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

Journal Article · · Environ. Sci. Technol.; (United States)
DOI:https://doi.org/10.1021/es00174a015· OSTI ID:6146971
Photolysis of carboxylate anions adsorbed onto highly crystalline goethite (..cap alpha..-FeOOH) with 300-400-nm light produces Fe/sup 2 +/(aq) and /sup ./OH from surface and solution redox reactions. The production of Fe/sup 2 +/(aq) and /sup ./OH was studied in N/sub 2/-purged and aerated aqueous suspensions, respectively, of goethite containing equimolar (10/sup -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 /sup ./OH. Fe/sup 2 +/(aq) was determined colorimetrically. A proposed reaction mechanism includes the photoexcitation of Fe(III) surface complexes with OH/sup -/, HCO/sub 3//sup -/, and RCOO/sup -/ ligands to form Fe/sup 2 +/(aq) and corresponding ligand radicals. Additional /sup ./OH is made by the O/sub 2/ oxidation of Fe/sup 2 +/(aq). Comparison of Fe/sup 2 +/(aq) and /sup ./OH yields permitted an estimate of the relative importance of pathways leading to /sup ./OH.
Research Organization:
Geological Survey, Denver, CO (USA)
OSTI ID:
6146971
Journal Information:
Environ. Sci. Technol.; (United States), Journal Name: Environ. Sci. Technol.; (United States) Vol. 22:9; ISSN ESTHA
Country of Publication:
United States
Language:
English