Effect of Silicate Species on the Transformation of Ferrihydrite into Goethite and Hematite in Alkaline Media

Cornell, R. M.

doi:10.1346/ccmn.1987.0350103

Cited by 213 publications

(163 citation statements)

References 31 publications

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“…Also, the relative position of hydroxyl groups on the surface is presumably altered, possibly leading to different sorption properties as compared to pure goethite. The incorporation of Si did not cause any change of the unit-cell dimensions as also shown by Cornell et al (1987) and Quin et al (1988). This indicates that the close association of this element with goethite occurs by occlusion and not by isomorphous substitution.…”

Section: Characteristics Of the Goethitessupporting

confidence: 57%

“…In the presence of Si relatively large crystals are formed (sample GSi: length ~600 nm, width ~ 200 nm) which are multi-domainic (Figure 2). This effect could be due to the presence of strongly sorbing silicate anions linking together goethite particles (Cornell et al 1987, Quin et al 1988. Furthermore, this sample exhibited the smallest X R D line-broadening of all samples.…”

Section: Characteristics Of the Goethitesmentioning

confidence: 89%

“…Thin sections of Si associated goethites show a mottled contrast (Smith and Eggleton 1983) which is indicative of discontinuities in the structure. The difficulty of incorporating Si into octahedral coordination in the goethite structure is a consequence of its strong preference for tetrahedral coordination (Cornell et al 1987).…”

Section: Characteristics Of the Goethitesmentioning

confidence: 99%

“…Among those are elements like Co, Cu and Cd, which can be incorporated by isomorphous substitution (Gerth 1990, Kumar et al 1990. On the other hand, Si seriously retards goethite crystallization and seems to be incorporated in goethite because of occlusion (Cornell et al 1987, Quin et a11988, Gerth et al 1993. Natural goethites were found to contain up to 7% SiO2 (Fordham and Norrish 1983).…”

Section: Introductionmentioning

confidence: 99%

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Retention of Cobalt by Pure and Foreign-Element Associated Goethites

Bibak¹,

Gerth

Borggaard³

1995

Clays and clay miner.

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Abstract--Retention studies of the cobalt-goethite system were carried out using synthetic, star-shaped and lath-shaped pure, AI-, Cd-, Cu-and Si-associated goethites. Aluminium and Si are commonly occurring foreign elements in natural goethites. The goethites were prepared by coprecipitating Fe and the foreign element under controlled conditions and characterized by X-ray diffraction, transmission electron microscopy, specific surface area determination and 2 M HC1 extraction. The foreign-element associated goethites contained ~3, ~5 and ~9 mole % A1, ~4 mole % Cd and ~3 mole % Cu incorporated by isomorphous substitution but only ~0.4 mole % of probably occluded Si. Crystal size and shape but also number of defects and domains, and hence specific surface area, unit-cell dimensions and reactivity towards 2 M HC1, exhibited great variability among the goethites. Accordingly the amounts of Co sorbed from initially 10 -7 M Co in 0.1 M Ca(NO3)2 in relation to pH (3-8) and reaction time (2-504 h) were very different for the eight gnethites. The affinity of Co is highest for Cd-and lowest for Cu-gnethite. These samples also form the extremes regarding time-dependent sorption with Cu-goethite showing the smallest and Cd-goethite the largest increase in sorption with increasing reaction time. The Co uptake was not caused by precipitation Co(III) oxides due to Co(II) oxidation, since oxygen exclusion during sorption had no effect on the amount of Co sorbed. The amounts of sorbed Co extracted by 2 M HC1 decreased with increasing sorption time but 40--87% of sorbed Co remained unextracted after 48 h, most in Cu-goethite and least in lath-shaped pure goethite. The strong retention suggests Co uptake by diffusion into micropores and fissures resulting from structural defects and intergrowths. The diffusion coefficients range from 3.10-19 to 6.10 -17 cm2/s with the highest values for A1-and Si-associated gnethites emphasizing the importance for Co immobilization, and hence availability, of foreign-element associations in goethite.

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Section: Characteristics Of the Goethitessupporting

confidence: 57%

Section: Characteristics Of the Goethitesmentioning

confidence: 89%

Section: Characteristics Of the Goethitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Retention of Cobalt by Pure and Foreign-Element Associated Goethites

Bibak¹,

Gerth

Borggaard³

1995

Clays and clay miner.

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“…TEMs of samples taken during the earliest stages of the reaction showed that birnessite formed simultaneously with or even before hausmannite. Apparently, this birnessite formed by disproportionation from Mn(III) produced by oxidation of Mn(II) at the akaganrite surface: earlier studies (CorneU and Giovanoli, 1987) showed that addition ofMn 3 § solution (0.01 M) to KOH (0.01-1 M) led to rapid precipitation of birnessite. In the present work, more birnessite formed initially in the presence of high-surface-area, than lowsurface-area akaganrite, which is consistent with more extensive adsorption and, hence, oxidation of Mn(II) by the high-surface-area iron oxide.…”

Section: Reaction Products (Table 1)mentioning

confidence: 95%

Transformation of Akaganéite Into Goethite and Hematite in the Presence of Mn

Cornell

Giovanoli

1991

Clays and clay miner.

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Abstract--The interaction of Mn and akagan6ite in neutral to alkaline media has been investigated using X-ray powder diffraction and transmission electron microscopy. Akagan6ite transformed into goethite and/or hematite, whereas Mn precipitated as hausmannite and bimessite at pH > 12 and as manganite at pH 7.5-8.5. Mn influenced the kinetics of the transformation of akagan6ite: the rate-determining step, i.e., the dissolution of akagan6ite, was retarded by adsorbed Mn species. Hematite formation was not suppressed. By catalyzing the air oxidation of adsorbed Mn(II), akagan6ite promoted the formation of birnessite. Akagan6ite did not retard recrystallization of the Mn phases. The incorporation of Mn in the structure of goethite fo.rmed in this system was negligible, and jacobsite (MnFe204) did not form. The formation of mixed Mn-Fe phases appeared to require a ratio of Mn 2+ : Fe to~ > 0.02; this ratio was not achieved due to the oxidation of Mn 2 § at the akagan6ite surface.

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New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

Laurila

Hannington

Leybourne

et al. 2015

Geochem Geophys Geosyst

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The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool‐type metal deposition. The deposit consists mainly of chemical‐clastic sediments with input from basin‐scale hydrothermal and detrital sources. A characteristic feature is the millimeter‐scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe‐(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main “ore” minerals. Mn‐oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe‐deposition and Mn‐deposition also alternated at the scale of individual laminae, reflecting short‐term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal‐bearing components, which formed by metal adsorption onto poorly crystalline Si‐Fe‐OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)‐carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe‐oxides. Permeable layers with abundant radiolarian tests were the focus for late‐stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

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Effect of Silicate Species on the Transformation of Ferrihydrite into Goethite and Hematite in Alkaline Media

Cited by 213 publications

References 31 publications

Retention of Cobalt by Pure and Foreign-Element Associated Goethites

Retention of Cobalt by Pure and Foreign-Element Associated Goethites

Transformation of Akaganéite Into Goethite and Hematite in the Presence of Mn

New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

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