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
Isomorphous substitution of iron for aluminium in some soil kaolinites
TL;DR: In this article, the results showed that iron was a structural constituent of the kaolinites in the Mysore Plateau (India), and the considerable amounts of iron extracted by the procedure and the closeness of the SiO2/R203 molar ratios (2.00-2.18) to the ideal value of 2.
Journal ArticleDOI
Soluble and particulate transfers of Cu, Cd, Al, Fe and some major elements in gravitational waters of a Podzol
TL;DR: In this article, the movement of particles moving in suspension through the soil can carry heavy metals with them, and they may be associated with these elements, and possibly the organic matter also, forming sesquioxide-organic complexes similar to those found in the solid phase of the soil.
Journal ArticleDOI
Lateritic and redoximorphic features in a faulted landscape near Manaus, Brazil
E. Fritsch,C. R. Montes-Lauar,C. R. Montes-Lauar,René Boulet,Adolpho José Melfi,Adolpho José Melfi,Etienne Balan,P. Magat +7 more
TL;DR: In this article, the authors describe and analyse the soils and sediments of the uplands in the Manaus region along a representative cross-section and identify two broad types of features, lateritic and redoximorphic.
14. eolian and silica deposition in the central north pacific: results from sites 885/8861
TL;DR: Sediments recovered at Ocean Drilling Program Sites 885/886 (central North Pacific Ocean at 44°41'N, 168°14'W and 44° 41'N and 168°16'W, respectively) record eolian deposition during the Cenozoic and late Mesozoic as discussed by the authors.
Journal ArticleDOI
Ecotoxicology of mercury in tropical forest soils: Impact on earthworms.
Andressa Cristhy Buch,George G. Brown,Maria Elizabeth Fernandes Correia,Lúcio Fábio Lourençato,Emmanoel V. Silva-Filho +4 more
TL;DR: The role of earthworms as environmental bioremediators was confirmed in this study, showing their ability to greatly bioaccumulate trace metals while reducing Hg availability in feces.
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.