Influence of Organic Anions on the Crystallization of Ferrihydrite

Cornell, R. M.

doi:10.1346/ccmn.1979.0270602

Cited by 199 publications

(126 citation statements)

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“…Moreover, the latter effect also depends on the pH. In the moderately acidic pH, phosphate favors the formation of hematite over goethite (Figure 3), probably by the mechanism discussed by Cornell and Schwertmann (1996), i,e., a phosphate ion adsorbed on ferrihydrite or on a small hematite nucleus acts as a template, in a way similar to oxalate and carboxylic and hydroxy-carboxylic acids that form binuclear surface complexes (Fischer and Schwertmann, 1975;Cornell and Schwertmann, 1979). Thus, the spindle-shaped and granular ellipsoidal hematite crystals produced in our experiments are similar to those synthesized, for example, in oxalate media (Fischer and Schwertmann, 1975).…”

Section: Discussionsupporting

confidence: 55%

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Gálvez

Barrón

Torrent

1999

Clays and clay miner.

123

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Abstract--We investigated the crystallization of ferrihydrite prepared by hydrolysis of Fe(NO3)3 solutions containing phosphate. Crystallization was studied at different pH (3-9), temperatures (298, 323, and 373 K), and initial P/Fe atomic ratios for periods to 730 d. Generally, crystallization was inhibited or only poorly crystallized lepidocrocite was formed at P/Fe > 2.5%. Phosphate favored the formation of hematite over goethite at all temperatures for most of the pH and P/Fe ranges investigated. This result is consistent with a model in which phosphate acts as a template for hematite formation, in analogy with other anions, such as oxalate. However, goethite was preferentially formed at alkaline pH and P/Fe > 1%, probably because high phosphate concentration resulted in a large increase in the negative charge of the ferrihydrite particles. This resulted in turn in less aggregation, a process that is known to precede dehydration to hematite. Phosphate greatly influenced the morphology of hematite and goethite. Hematite was often ellipsoidal or spindle-shaped. Twinned goethite crystals with a hematite core were formed at alkaline pH at P/Fe > 1%. Both hematite and goethite particles incorporated phosphate in an occluded form not desorbable by repeated alkali treatments.

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Section: Discussionsupporting

confidence: 55%

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Gálvez

Barrón

Torrent

1999

Clays and clay miner.

123

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“…• the content of total nitrogen (tn) by means of the Kjeldahl method [2], • the content of total iron and aluminium (Fe t , Al t ) by means of the microwave plasma atomic emission spectrometry (Agilent 4100 MP-AES) after samples digestion in a mixture of 60% hClO 4 and 40% hF,…”

Section: Soil Sampling and Analysismentioning

confidence: 99%

Characteristics of Iron and Aluminium Forms and Quantification of Soil Forming Processes in Chernozems in Western Slovakia

Jończak

Šimanský

2016

pjss

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Abstract. the studies on iron and aluminium forms and soil forming processes quantification in Chernozems were conducted in two localities in Western Slovakia. two soil pits were done in a complex of arable haplic Chernozems in Krakovany and two soil pits representing arable and forest Cambic Chernozems were done in Báb. the soils were sampled every 10 cm and analysed using standard methods. Based on analytical results, profile development indices (PDI) were calculated for each profile. Chernozems in Krakovany were characterised by 90 cm (Krakovany 1) and 80 cm (Krakovany 2) thick solums and ph increasing with depth from neutral to alkaline. the content of total organic carbon (tOC) was up to 13.70 g kg -1 in both profiles. Cambic Chernozems in Báb were characterised by a lower thickness of solum -40 cm in arable soil (Báb 1) and 70 cm in forest soil (Báb 2). Reaction of arable soil ranged from slightly acid to alkaline, and in the case of forest soil -from strongly acid to alkaline. Arable soil contained 14.2-14.5 g kg -1 , and forest soils 12.9-50.7 g kg -1 of tOC in A horizons. the content of Fe t in the studied soils ranged from 21.78 to 32.48 g kg . Fe d /Fe t ratios ranged from 0.26 to 0.39. Crystalline forms predominated over amorphous ones. the values of PDI were relatively low, namely 1.50 -in the profile Krakovany 1; 1.76 -in the profile Krakovany 2; 1.15 in the profile Báb 1 and 2.12 -in the profile Báb 2.

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“…Studies of the effect of foreign ions have contributed to an understanding of the mechanisms of the transformation of ferdhydrite to goethite and hematite (Fisher and Schwertmann, 1975;Cornell and Schwertmann, 1979;Cornell, 1985). The only cationic species that has been considered in detail in affecting the formation of Fe oxides is A1 although recently, CorneU andGiovanoli (1987, 1988) studied the influence of Mn and Cu in the transformation of ferdhydrite.…”

Section: Introductionmentioning

confidence: 99%

Influence of Mn²⁺ and pH on the Formation of Iron Oxides from Ferrous Chloride and Ferrous Sulfate Solutions

Krishnamurti

1989

Clays and clay miner.

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Abstract--The influence of Mn 2 § on the formation of Fe oxides at pHs of 6.0 and 8.0 and varying Mn/ Fe molar ratios (0, 0.1, 1.0, and 10.0) in the FeC12-NH4OH and FeSO4-NH4OH systems was studied by X-ray powder diffraction (XRD), infrared absorption, transmission electron microscopic, and chemical analyses. In the absence of Mn ~+, lepidocrocite (-t-FeOOH) and maghemite ('y-Fe203) were the crystalline species formed at pHs of 6.0 and 8.0, respectively, in the FeC12 system, whereas lepidocrocite and goethite (a-FeOOH) and lepidocrocite were the crystalline species formed at pHs of 6.0 and 8.0, respectively, in the FeSO4 system. The amount of Mn coprecipitated with Fe (as much as 8.1 mole % in the FeC12 system and 15.0 mole % in the FeSO4 system) increased as the initial solution Mn/Fe molar ratio increased from 0 to 10.0, resulting in the perturbation of the crystallization processes of the hydrolytic products of Fe formed. At pH 6.0, the perturbation led to the formation of poorly ordered lepidocrocite, as reflected in the increasing broadening of its characteristic peaks in the XRD patterns. At pH 8.0, poorly ordered iepidocrocite and a honessite-like mineral (Mn-Fe-SO4-H20) formed in the FeC12 and FeSO4 systems, respectively.

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Influence of Organic Anions on the Crystallization of Ferrihydrite

Cited by 199 publications

References 12 publications

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Characteristics of Iron and Aluminium Forms and Quantification of Soil Forming Processes in Chernozems in Western Slovakia

Influence of Mn²⁺ and pH on the Formation of Iron Oxides from Ferrous Chloride and Ferrous Sulfate Solutions

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Influence of Organic Anions on the Crystallization of Ferrihydrite

Cited by 199 publications

References 12 publications

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Effect of Phosphate on the Crystallization of Hematite, Goethite, and Lepidocrocite from Ferrihydrite

Characteristics of Iron and Aluminium Forms and Quantification of Soil Forming Processes in Chernozems in Western Slovakia

Influence of Mn2+ and pH on the Formation of Iron Oxides from Ferrous Chloride and Ferrous Sulfate Solutions

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Influence of Mn²⁺ and pH on the Formation of Iron Oxides from Ferrous Chloride and Ferrous Sulfate Solutions