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
Pedogeochemical characteristics of chromite in a paddy soil derived from serpentinites
Zeng-Yei Hseu,Yoshiyuki Iizuka +1 more
TL;DR: In this paper, the micromorphological characteristics of chromite and identified chromite weathering as a source of Cr in a paddy soil profile derived from serpentinites in Eastern Taiwan.
Journal ArticleDOI
The behavior of heavy metals in tidal flat sediments during fresh water leaching
TL;DR: It is suggested that leaching with fresh water can also remove a fraction of the heavy metal contamination when it diminishes sediment salinity.
Journal ArticleDOI
Nickel accumulation in paddy rice on serpentine soils containing high geogenic nickel contents in Taiwan
Zeng-Yei Hseu,Yun-Jie Lai +1 more
TL;DR: The accumulation ability of rice roots was much higher than that of its shoots; however, compared with those reported previously, brown and polished rice samples contained much higher Ni concentrations, within the ranges of 1.50–4.53 and 2.45–5.54 mg/kg, respectively.
Book ChapterDOI
Argillic Horizons in Modern Loess Soils in an Ustic Soil Moisture Regime: Comparative Studies in Forest-Steppe and Steppe Areas from Eastern Europe and the United States
TL;DR: In this paper, the authors investigate the causal relationship between the soil-forming factors and the regular spatial distribution pattern of soils, using the expression "structure of the soil cover".
Journal ArticleDOI
Iron oxides dynamics in a subtropical Brazilian Paleudult under long-term no-tillage management
TL;DR: In this paper, the effect of no-tillage management on the content and distribution of types of iron oxides in a Rhodic Paleudult in southern Brazil was investigated.
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.