Journal ArticleDOI
Iron Oxide Removal from Soils and Clays by a Dithionite-Citrate System Buffered with Sodium Bicarbonate
TLDR
In this article, the bicarbonate-buffered Na2S2O4-citrate system was used for removing free iron oxides from latosolic soils, and the least destructive of iron silicate clays.Abstract:
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.read more
Citations
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Book ChapterDOI
X-ray Diffraction Procedures for Clay Mineral Identification
G. Brown,G. W. Brindley +1 more
Journal ArticleDOI
Nitrate Reduction in an Unconfined Sandy Aquifer: Water Chemistry, Reduction Processes, and Geochemical Modeling
TL;DR: In this article, a series of eight multilevel samplers along a flow line, deriving water from both arable and forested land, were used to investigate the distribution and reduction of nitrate in an unconfined sandy aquifer.
Journal ArticleDOI
The cycling of iron in natural environments : considerations based on laboratory studies of heterogeneous redox processes
Werner Stumm,Barbara Sulzberger +1 more
TL;DR: The various pathways for the oxygenation of ferrous iron and for the dissolution of Fe(III) (hydr) oxides, especially by reducing ligands with oxygen donor atoms in thermal and photochemical processes, are assessed on the basis of laboratory experiments for application to natural systems.
Journal ArticleDOI
A critical look at iron paleoredox proxies: New insights from modern euxinic marine basins
Timothy W. Lyons,Silke Severmann +1 more
TL;DR: In this paper, the authors show that high siliciclastic accumulation rates can swamp the enrichment mechanism, resulting in only intermediate DOP values for euxinic sediments and FeT/Al ratios that mimic the oxic shelf.
Journal ArticleDOI
Environmental magnetism: Principles and applications
Qingsong Liu,Andrew P. Roberts,Juan C. Larrasoaña,Subir K. Banerjee,Yohan Guyodo,Lisa Tauxe,Frank Oldfield +6 more
TL;DR: In this article, a review of magnetic properties and the environmental processes that give rise to the measured magnetic signal is presented, and the power of environmental magnetism in enabling quantitative environmental interpretations is discussed.
References
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Book
Soil Chemical Analysis
TL;DR: Soil chemical analysis, Soil Chemical Analysis (SCA), this paper, is a technique for soil chemical analysis that is used in the field of Soil Chemistry and Chemical Engineering.
Journal ArticleDOI
Iron Oxide Removal from Soils and Clays1
N. H. Aguilera,M. L. Jackson +1 more
TL;DR: In this article, a procedure is presented which employs sodium dithionite (Na2S2O4, hyposulfite, or "hydrosulfite") as the reductor, and 0.3 molar citrate with or without Fe-3 specific Versene as the chelating reagent.