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
Phosphorus Sorption and Availability from Biochars and Soil/Biochar Mixtures
Rajesh Chintala,Thomas E. Schumacher,Louis M. McDonald,David E. Clay,Douglas D. Malo,Sharon K. Papiernik,Sharon A. Clay,James Julson +7 more
TL;DR: In this article, the authors quantify the P sorption and availability from biochars produced from the fast pyrolysis of corn stover (Zea mays L.), Ponderosa pine (Pinus ponderosa Lawson and C. Lawson), and switchgrass (Panicum virgatum L.).
Journal ArticleDOI
Urban soil contamination in Bangkok : heavy metal and aluminium partitioning in topsoils
TL;DR: In this paper, the extent and severity of surface soil contaminations from urban parts of the Bangkok metropolitan region was assessed by sampling 30 soils at 0-5 cm depth along a N-S-bound ''main axis'' with ''suburb', ''central'' and ''industrial'' branches at a right angle.
Journal ArticleDOI
Sol–gel transitions of sodium montmorillonite dispersions
S. Abend,Gerhard Lagaly +1 more
TL;DR: The flow behavior of sodium montmorillonite dispersions at salt concentrations below the critical coagulation concentration is determined by the influence of the ionic double layers on the mobility of the particles (secondary electroviscous effect) as mentioned in this paper.
Journal ArticleDOI
Influence of organic matter on phosphate adsorption by aluminium and iron oxides in sandy soils
TL;DR: In this paper, the phosphate adsorption capacity (Pmax) of samples from various horizons of five Danish podzolized soils were investigated before and after organic matter removal.
Journal ArticleDOI
Review of methodologies for extracting plant-available and amorphous Si from soils and aquatic sediments
TL;DR: There is a variety of methodologies used in the aquatic sciences and soil sciences for extracting different forms of Si from sediments and soils as mentioned in this paper, however, a comparison of the published extraction techniques is lacking.
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.