Photo-Induced Reductive Dissolution of Hematite (α-Fe₂O₃) by S(IV) Oxyanions

Citation

Faust, Bruce Charles (1985) Photo-Induced Reductive Dissolution of Hematite (α-Fe₂O₃) by S(IV) Oxyanions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/cj3r-5x15. https://resolver.caltech.edu/CaltechETD:etd-03262008-141334

Abstract

The kinetics and mechanism of the photo-induced reductive dissolution of hematite (α-Fe₂O₃) by S(IV) oxyanions, in aqueous suspensions of hematite, have been investigated. Experimental quantum yields for Fe(II)_aq production are reported for deoxygenated hematite suspensions containing S(IV). Quantum yield studies together with spectroscopic information indicate that ≡Fe(III)-S(IV) surface complexes undergo a photo-induced ligand to metal charge transfer reaction resulting in the reductive dissolution of hematite and production of Fe(II)_aq.

The autoxidation of S(IV) in oxygenated hematite suspensions exhibits autocatalytic behavior. This behavior is interpreted in terms of three general processes: i) production of Fe(II)_aq from photo-induced ligand to metal charge transfer reactions of ≡Fe(III)-S(IV) surface complexes, ii) oxidation of Fe(II)_aq to Fe(III)_aq and, iii) the Fe(III)_aq catalyzed autoxidation of S(IV). A numerical model, based on these processes, is developed to predict the disappearance of S(IV) in oxygenated hematite suspensions under illumination.

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