HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brennan, E. W. Articles by Lindsay, W. L. Search for Related Content PubMed Articles by Brennan, E. W. Articles by Lindsay, W. L. GeoRef GeoRef Citation Agricola Articles by Brennan, E. W. Articles by Lindsay, W. L.

Reduction and Oxidation Effect on the Solubility and Transformation of Iron Oxides

Highland Community College, Highland, KS

W. L. Lindsay^*

Dep. Soil and Crop Sciences, Colorado State Univ., Fort Collins, CO 80523-1170

*Corresponding author (wlindsay{at}agsci.colostate.edu).

ABSTRACT

Reports on the solubility of Fe during fluctuating redox conditions in soils and sediments are often difficult to interpret. This study was undertaken to examine the solubility relationships of Fe in suspensions of amorphous Fe(OH)₃, Fe₂O₃(hematite), and soils subjected to changing redox conditions. A decrease in pe + pH was accomplished by the addition of organic matter and H₂(g) in soils, and by H₂(g) with a Pt catalyst in Fe(III) oxide suspensions. Addition of H₂(g) and a Pt catalyst to Fe(III) oxide suspensions resulted in their dissolution and subsequent precipitation of two distinct Fe₃O₄ products. With small additions of O₂ (0.2 mL of air), equilibrium was maintained with Fe₃O₄(magnetite). X-ray diffraction confirmed its presence. When large amounts of atmospheric O₂(g) were added (15 mL of air), the precipitate designated Fe₃O₄(amorp) was formed with a mean log of the equilibrium constant based on activities (K^o) of 40.65 ± 0.11. X-ray diffraction showed this precipitate to be amorphous. This precipitate controlled Fe solubility within the pe + pH range of 4.0 to 12.7. In soil suspensions subject to changing redox, the Fe₃O₄(amorp) precipitate and Fe(OH)₃(amorp) appear to control Fe solubility. Crystalline Fe(III) oxides including Fe₂O₃(hematite) and FeOOH(goethite) can only control Fe solubility under more highly stable, oxidizing conditions. Only with prolonged and intensive reduction is Fe₃O₄(magnetite) expected to form and control Fe solubility.

Received for publication March 24, 1997.

This article has been cited by other articles:

				G. C. Murray and D. Hesterberg Iron and Phosphate Dissolution during Abiotic Reduction of Ferrihydrite-Boehmite Mixtures Soil Sci. Soc. Am. J., June 21, 2006; 70(4): 1318 - 1327. [Abstract] [Full Text] [PDF]

				M. Shenker and P. R. Bloom Comments on "Amounts, Forms, and Solubility of Phosphorus in Soils Receiving Manure" Soil Sci. Soc. Am. J., June 28, 2005; 69(4): 1353 - 1354. [Full Text] [PDF]

				K. M. Catlett, D. M. Heil, W. L. Lindsay, and M. H. Ebinger Soil Chemical Properties Controlling Zinc2+ Activity in 18 Colorado Soils Soil Sci. Soc. Am. J., July 1, 2002; 66(4): 1182 - 1189. [Abstract] [Full Text] [PDF]