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
Effects of vegetation type on soil resistance to erosion: Relationship between aggregate stability and shear strength
M. Fattet,Yuxi Fu,Muriel Ghestem,Wenyong Ma,M. Foulonneau,Jérôme Nespoulous,Y. Le Bissonnais,Alexia Stokes +7 more
TL;DR: In this article, the effect of vegetation on both soil aggregate stability and shear strength was investigated in former croplands converted to vegetated erosion protection areas within the context of China's sloping land conversion program.
Journal ArticleDOI
The geochemistry of mercury in central amazonian soils developed on the Alter-do-Chão formation of the lower Tapajós River Valley, Pará state, Brazil
Michel Roulet,Marc Lucotte,A. Saint-Aubin,S. Tran,Isabelle Rheault,N. Farella,E. de Jesus da Silva,J. Dezencourt,C.-J. Sousa Passos,G. Santos Soares,Jean Remy Davée Guimarães,Donna Mergler,M. Amorim +12 more
TL;DR: The sandification and podzolisation that is characteristic of the evolution of numerous pedological systems in the equatorial Amazon could be responsible for exportation of the naturally accumulated Hg by acidic complexation and migration to the black waters of the Amazon.
Journal ArticleDOI
Adsorption of lead, copper, zinc, cobalt, and cadmium by soils that differ in cation-exchange materials
Aly Abd-Elfattah,Koji Wada +1 more
TL;DR: In this paper, the adsorption of Zn2+, Pb2+, Cu2+, Co2+, and Cd2+ (M2+) by soils was measured at concentrations ranging from 10-7 to 10-2 M in 10-3 to 10 -2 M CaCI2.
Journal Article
Morphology and composition of allophane
Teruo Henmi,K. Wada +1 more
TL;DR: In this paper, electron micrographs of coarse clays (0.2-2 prm) showed that allophane forms within weathered glass shards, and the content of aluminum in 4-fold coordination in alophane increased with its SiOr/AlrOB ratio and amounted to 50 percent of the total aluminum.
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.