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
Scanning Electron Microscopy–Energy Dispersive Scan Analyses and Rheological Investigations of South-Brazilian Soils
Wibke Markgraf,Rainer Horn +1 more
TL;DR: In this paper, the influence of soil organic matter (SOM), Fe oxides, and clay minerals on micromechanical shear behavior under oscillation were tested under saturated and predrained (at -60 hPa) conditions.
Journal ArticleDOI
Soil formation and its implications for stabilization of soil organic matter in the riparian zone
TL;DR: In this article, the authors investigated the influence of flooding conditions on the stabilization of soil organic matter (SOM) in the riparian zone of the Danube near Vienna (Austria).
Journal ArticleDOI
Phosphate sorption by calcite, and iron-rich calcareous soils
Ming-Kuang Wang,Yu-Min Tzou +1 more
TL;DR: In this paper, the results of high-gradient magnetic separation (HGMS) were used to fractionate soil clays into magnetic and tailing fractions, and the results could be put into the Langmuir equation.
Journal ArticleDOI
Insulating properties of clay films towards Fe(CN)63− as affected by electrolyte concentration
Alanah Fitch,Carol L. Fausto +1 more
Journal ArticleDOI
Sedimentary processes on the Bengal continental shelf as revealed by clay-size mineralogy
M.P. Segall,Steven A. Kuehl +1 more
TL;DR: In this paper, the authors examined sediment dispersal seaward of the Ganges-Brahmaputra river system through analysis of sediment cores and surface grab samples for clay-size mineralogy.
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.