Hostname: page-component-78c5997874-j824f Total loading time: 0 Render date: 2024-11-10T09:31:46.475Z Has data issue: false hasContentIssue false
  • English
  • Français

Iron Oxide Removal from Soils and Clays by a Dithionite-Citrate System Buffered with Sodium Bicarbonate

Published online by Cambridge University Press:  01 January 2024

O. P. Mehra  and
M. L. Jackson
O. P. Mehra
Affiliation:
Department of Soils, University of Wisconsin, Madison, Wisconsin, USA
M. L. Jackson
Affiliation:
Department of Soils, University of Wisconsin, Madison, Wisconsin, USA
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The oxidation potential of dithionite (Na2S2O4) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na2S2O4 oxidized. Tests show that NaHCO3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline goethite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays.

A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na2S2O4-citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was about 17 percent as contrasted to 35–80 percent with other methods.

Type
Article
Information
Clays and Clay Minerals (National Conference on Clays and Clay Minerals) , Volume 7 , February 1958 , pp. 317 - 327
Copyright
Copyright © Clay Minerals Society 1958

References

Aguilera, N. E. and Jackson, M. L. (1953) Iron oxide removal from soils and clays: Soil Sci. Soc. Amer. Proc., v. 17, pp. 359–364.10.2136/sssaj1953.03615995001700040015xCrossRefGoogle Scholar
Allison, L. E. and Scarseth, G. D. (1942) A biological reduction method for removing free iron oxides from soils and colloidal clays: J. Amer. Soc. Agron., v. 34, pp. 616–623.10.2134/agronj1942.00021962003400070003xGoogle Scholar
Deb, B. C. (1950) The estimations of free iron oxide in soils and clays and their removal: J. Soil Sci., v. 1, pp. 212–220.10.1111/j.1365-2389.1950.tb00733.xCrossRefGoogle Scholar
Dion, H. G. (1944) Iron oxide removal from clays and its influence on base exchange properties and x-ray diffraction patterns of the clays: Soil Sci., v. 58, pp. 411–424.10.1097/00010694-194412000-00001CrossRefGoogle Scholar
Drosdoff, M. and Truog, E. (1955) A method for removing and determining the free iron oxide in soil colloids: J. Amer. Soc. Agron., v. 27, pp. 312–317.10.2134/agronj1935.00021962002700040011xCrossRefGoogle Scholar
Haldane, A. D. (1956) Determination of free iron oxide in soils: Soil Sci., v. 82, pp. 483–489.10.1097/00010694-195612000-00005CrossRefGoogle Scholar
Jackson, M. L. (1956) Soil Chemical Analysis—Advanced Course: Published by the author, Dept. of Soils, University of Wisconsin, Madison, Wisconsin, 991 pp.Google Scholar
Jackson, M. L. (1958) Soil Chemical Analysis: Prentice-Hall, Englewood Cliffs, New Jersey, 498 pp.Google Scholar
Jeffries, C. D. (1941) A method of preparing soils for petrographic analysis: Soil Sci., v. 52, pp. 451–454.10.1097/00010694-194112000-00004CrossRefGoogle Scholar
Jeffries, C. D. (1947) A rapid method for the removal of free iron oxides in soils prior to petrographic analysis: Soil Sci. Soc. Amer. Proc., v. 11, pp. 211–212.10.2136/sssaj1947.036159950011000C0039xCrossRefGoogle Scholar
Latimer, W. M. (1952) Oxidation Potentials: Prentice-Hall, New York, 392 pp.Google Scholar
Mackenzie, R. C. (1954) Free-iron oxide removal from soils: J. Soil Sci., v. 5. pp. 167–172.10.1111/j.1365-2389.1954.tb02185.xCrossRefGoogle Scholar
Mitchell, B. D., and Mackenzie, R. C. (1954) Removal of free-iron oxide from clays: Soil Sci., v. 77, pp. 173–184.10.1097/00010694-195403000-00001Google Scholar
Sawhney, B. L., Jackson, M. L. and Corey, R. B. (1959) Cation exchange determination of soils as influenced by the cation species: Soil Sci. v. 87, pp. 243–248.10.1097/00010694-195905000-00001CrossRefGoogle Scholar
Tamm, O. (1922) Eine Method zur Bestimmung der anorganischen Komponenten des Gelkomplex in Boden: Medd. statens skogforsoksanst, v. 19, pp. 385–404.Google Scholar
Truog, E., Taylor, J. R. Jr., Pearson, R. W., Weeks, M. E. and Simonson, R. W. (1937) Procedure for special type of mechanical and mineralogical soil analysis; Soil Sci. Soc. Amer. Proc., v. 1, pp. 101–112.10.2136/sssaj1937.03615995000100000013xCrossRefGoogle Scholar