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
Organo-mineral associations in sandy acid forest soils: importance of specific surface area, iron oxides and micropores
TL;DR: In this article, the importance of Fe oxides, short-range order Al silicates and the surface areas of minerals and micropores on the formation of organo-mineral associations was examined.
Journal ArticleDOI
Phosphorus binding by poorly crystalline iron oxides in North Sea sediments
TL;DR: In this article, differential X-ray powder diffraction (DXRD) and extraction procedures were used to characterize the iron oxides present in four sediments from contrasting environments in the North Sea.
Journal ArticleDOI
Zinc and Copper Solubility as a Function of pH in an Acid Soil1
M. B. McBride,J. J. Blasiak +1 more
TL;DR: In this paper, the effect of pH and competing cations on Zn/sup 2 +/ solubility in an acid mineral soil indicate the probable involvement of hydrous oxides of iron, aluminum, or manganese in the adsorption process.
Journal ArticleDOI
Climate extremes in Loess of China coupled with the strength of deep-water formation in the North Atlantic
Zhengtang Guo,Tungsheng Liu,Nicolas Fedoroff,Lanying Wei,Zhongli Ding,Naiqin Wu,Huoyuan Lu,Wenying Jiang,Zhisheng An +8 more
TL;DR: Xifeng, Changwu and Weinan as discussed by the authors showed that the Loess-paleosol sequences of the last 1.2 Ma in China have recorded two kinds of climate extremes: the strongly 18. developed S4, S5-1 and S 5-3 soils corresponding to the marine d O stages 11, 13, and 15, respectively as evidence of 18 three episodes of great warmth and two coarse-grained loess units L9 and L15, corresponding to marine dO stages 22,. 23, 24 and 38, respectively which indicate seve
Journal ArticleDOI
Heavy metals in coastal wetland sediments of the Pearl River Estuary, China
TL;DR: Sediment quality in coastal wetlands of the Pearl River Estuary was concerned since the wetlands were used for land reclamation, aquaculture and wildlife protection, and meanwhile served as one of the main ultimate sinks for large amount of heavy metals discharged from the rapidly developing Pearl River Delta.
References
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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.