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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Journal ArticleDOI
Microtextures on quartz grains in tills from Antarctica
TL;DR: In this article, replicated subsamples from tills emplaced by thick glaciers with both short and long transport distances were analyzed by scanning electron microscope (SEM) to test the hypothesis that relative ice thickness and distance of transport influence the type and range of microtextures observed on individual grains.
Journal ArticleDOI
Soil Characteristic Response Times and Pedogenic Thresholds during the 1000-Year Evolution of a Paddy Soil Chronosequence
Journal ArticleDOI
Hydrothermal clay mineral formation of East Pacific rise and Bauer Basin sediments
Gary M. McMurtry,Hsueh-Wen Yeh +1 more
TL;DR: In this article, surface metalliferous sediment recovered from the crest of the East Pacific Rise at 6°S and 10°S latitudes and from the adjacent Bauer Basin are characterized by an authigenically formed, Fe-rich montmorillonite that dominates the non-carbonate mineralogy of the clay fraction.
Journal ArticleDOI
Effect of different soil washing solutions on bioavailability of residual arsenic in soils and soil properties.
TL;DR: Overall, this study showed that treated soils having lower levels of contaminants could still exhibit toxic effects due to changes in soil properties, which highly depended on washing solutions.
Journal ArticleDOI
Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw.
Monique Sézanne Patzner,Carsten W. Mueller,Miroslava Malusova,Moritz Baur,Verena Nikeleit,Thomas Scholten,Carmen Hoeschen,James M. Byrne,James M. Byrne,Thomas Borch,Andreas Kappler,Casey Bryce,Casey Bryce +12 more
TL;DR: It is shown that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost, which leads to an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient.
References
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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.