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
More filters
Journal ArticleDOI
Rheological stabilization of wet soils by model root and fungal exudates depends on clay mineralogy
Pierre Barré,Paul D. Hallett +1 more
TL;DR: In this paper, the root mucilage analogue (polygalacturonic acid, PGA) and a fungal polysaccharide (scleroglucan) were studied for a range of soils with different clay mineralogies.
Journal ArticleDOI
Distribution of soil organic matter between fractions and aggregate size classes in grazed semiarid steppe soil profiles
TL;DR: In this article, the authors applied a combined aggregate size, density and particle size fractionation procedure to sandy steppe soils under different grazing intensities (continuously grazed = Cg, winter grazing = Wg, ungrazed since 1999 = Ug99, since 1979 = Ug79).
Journal ArticleDOI
Robust geochemical indices for redox and weathering on a granitic laterite landscape in Central Uganda
TL;DR: In this article, a suite of robust geochemical indices for landscape-scale analysis of weathering and oxidation-reduction (redox) processes in laterite formation is presented.
Journal ArticleDOI
Bioaccessibility of arsenic in mine waste-contaminated soils: a case study from an abandoned arsenic mine in SW England (UK).
Barbara Palumbo-Roe,Ben Klinck +1 more
TL;DR: Mine soils from Devon Great Consols Mine showed overall higher As bioaccessibility (15%) than other mineralised soils not affected by mining activities and background soils within the Tamar Catchment whose percent bioaccessible As median values were 9%.
Journal ArticleDOI
Covalent Grafting to μ-Hydroxy-Capped Surfaces? A Kaolinite Case Study
TL;DR: All μ-hydroxyl groups are frequently encountered capping groups found on the external surfaces of various minerals that are often used as fillers in composite materials as mentioned in this paper, and Covalent grafting to this f...
References
More filters
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.