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
Pedogenic and lithogenic contributions to the magnetic susceptibility record of the Chinese loess/palaeosol sequence
TL;DR: In this paper, the magnetic properties of 69 loess and palaeosol samples from the loess plateau in China were studied, and it was shown that approximately two-thirds of the total iron in these samples exists as paramagnetic iron in silicate minerals.
Journal ArticleDOI
Characterization of clay–organic‐matter complexes resistant to oxidation by peroxide
TL;DR: In an acid soil, amounts or organic carbon resistant to peroxidation with hydrogen peroxide were strongly related to the proportions of expandable phyllosilicate (vermiculite, smectite) in the clay fraction, as measured by its K2O content and cation exchange capacity as discussed by the authors.
Journal ArticleDOI
Characterization of primary and secondary magnetite in marine sediment by combining chemical and magnetic unmixing techniques
Peter Ludwig,Ramon Egli,Shawn Bishop,Volodymyr A. Chernenko,Thomas Frederichs,Georg Rugel,Silke Merchel,María Julia Orgeira +7 more
TL;DR: In this article, Hu et al. presented a novel technique for quantitative unmixing of primary and secondary ferrimagnetic minerals in sediments, which is suitable for the search for cosmogenic 60 Fe signatures from supernova explosions, because 60 Fe dilution by dissolved primary Febearing minerals is minimized.
Journal ArticleDOI
Mobility of Ni, Cr and Co in serpentine soils derived on various ultrabasic bedrocks under temperate climate
TL;DR: In this article, the authors analyzed the mobility of Ni, Cr and Co in six serpentine sites derived from a variety of parent substrates: from partially serpentinized peridotites through serpentinites containing relics of primary minerals and textures to proper serpentinite.
Journal ArticleDOI
Coupled dynamics of iron and iron-bound organic carbon in forest soils during anaerobic reduction
Qian Zhao,Dinesh Adhikari,Rixiang Huang,Aman Patel,Xilong Wang,Yuanzhi Tang,Daniel Obrist,Eric E. Roden,Yu Yang +8 more
TL;DR: In this article, the authors investigated the dynamics of Fe and organic carbon (OC) in four forest soils in the presence of the dissimilatory Fe-reducing bacterium, Shewanella oneidensis MR-1.
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.