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
Use of partial dissolution techniques in geochemical exploration
TL;DR: Partial dissolution techniques are classified as single dissolution or sequential multiple dissolution depending on the number of steps taken in the procedure, or as nonselective extraction and as "selective" extraction in terms of the relative specificity of the extraction as mentioned in this paper.
Journal ArticleDOI
Sorption of DOM and DOM fractions to forest soils
TL;DR: In this article, the sorption of total, hydrophilic, and hydrophobic dissolved organic matter (DOM) on 125 forest soil samples was studied in batch experiments, where the soil samples represented the main soil orders of temperate climatic zones.
Journal ArticleDOI
Bacterial reduction of crystalline Fe (super 3+) oxides in single phase suspensions and subsurface materials
John M. Zachara,James K. Fredrickson,Shu-Mei Li,David W. Kennedy,Steven C. Smith,Paul L. Gassman +5 more
TL;DR: In this article, a dissimilatory Fe reducing bacterium (Shewanella putrefaciens, strain CN32) was used to reduce synthetic and geologic Fe{sup 3+} oxides associated with four Pleistocene-age, Atlantic coastal plain sediments.
Journal ArticleDOI
Recent progress in understanding physical and chemical properties of African and Asian mineral dust
Paola Formenti,Lothar Schütz,Yves Balkanski,Karine Desboeufs,Martin Ebert,Konrad Kandler,Andreas Petzold,Dirk Scheuvens,Dirk Scheuvens,Stephan Weinbruch,Daizhou Zhang +10 more
TL;DR: A review of recently acquired knowledge on the physico-chemical properties of mineral dust from Africa and Asia based on data presented and discussed during the Third International Dust Workshop, held in Leipzig (Germany) in September 2008 is presented in this paper.
Journal ArticleDOI
Controlled variation of redox conditions in a floodplain soil: Impact on metal mobilization and biomethylation of arsenic and antimony
TL;DR: An automated biogeochemical microcosm system allowing the control of redox potential (E H ) in soil suspensions was used to assess the effect of E H on the mobility of cadmium (Cd), copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), and manganese (Mn) as well as on the methylation of arsenic (As) and antimony (Sb) in a contaminated and slightly acidic floodplain soil as discussed by the authors.
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.