A study of the non-stoichiometrical halogen and water content of β-FeOOH

Chambaere, D.; Grave, E. De

doi:10.1002/pssa.2210830109

Cited by 26 publications

(18 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Analysis of akaganeite‐free pH 0 4/Cl 0.02 M, pH 0 6/Cl 0.02 M, and pH 0 8/Cl 0.02 M samples showed that little Cl − (≤0.3 wt %) was associated with Fe(III) (hydr)oxides (Figure a and Table ) in agreement with our previous observations (Peretyazhko et al, ). We, therefore, assume that chloride detected in akaganeite mixtures was associated with akaganeite tunnels, although we cannot exclude minor amount of Cl − adsorbed onto akaganeite surfaces (Chambaere & Degrave, ).…”

Section: Resultsmentioning

confidence: 99%

Effect of Solution pH and Chloride Concentration on Akaganeite Precipitation: Implications for Akaganeite Formation on Mars

et al. 2018

View full text Add to dashboard Cite

Akaganeite, a chloride-bearing Fe(III) (hydr)oxide, has been reported on Mars in Yellowknife Bay in Gale crater by X-ray diffraction (XRD), in Robert Sharp crater by Compact Reconnaissance Imaging Spectrometer for Mars, and possibly at the Gusev crater and Meridiani Planum by combined Mössbauer and bulk chemistry analyses. Because formation conditions remain unknown, we investigated akaganeite precipitation as a function of solution pH and chloride concentration. Akaganeite was synthesized through hydrolysis of Fe(III) perchlorate in the presence of 0.02, 0.05, and 0.1 M chloride and at initial solution pH of 1.6, 4, 6, and 8 at 90°C. Mineralogy of the precipitated Fe(III) (hydr)oxides was characterized by XRD, infrared spectroscopy, and Mössbauer spectroscopy. Total chloride and perchlorate contents were determined by ion chromatography. XRD revealed that akaganeite formed alone or in mixtures with ferrihydrite, hematite, and/or goethite at initial pH 1.6 with 0.02, 0.05, and 0.1 M Cl À and at initial pH from 4 to 8 with 0.05 and 0.1 M Cl À . Infrared analysis showed that akaganeite bands at~2 and~2.45 μm were sensitive to amount of akaganeite, total chloride content, and presence of other Fe(III) (hydr)oxides. The results indicate that akaganeite in Yellowknife Bay in Gale crater likely formed under acidic to alkaline (1.6 < pH < 8) oxidizing conditions in solutions containing >0.05 M Cl À by the dissolution of basaltic minerals. Akaganeite in Robert Sharp crater may have formed in acidic (pH < 4) solutions with~0.1 M Cl À through oxidative dissolution of Fe(II) sulfides and/or acidic oxidizing dissolution of basalts.Plain Language Summary Akaganeite, a chloride-bearing Fe(III) (hydr)oxide, has been reported in several locations (e.g., Gale and Robert Sharp craters) on Mars, but formation conditions are unknown. The objective of this work was to investigate formation of akaganeite at variable pH and dissolved chloride concentrations and to characterize the past aqueous conditions in the locations where akaganeite was detected on Mars. We found that akaganeite on Mars could form under substantially different environmental conditions. Akaganeite in Yellowknife Bay likely formed under acidic to alkaline moderately saline conditions by the dissolution of basaltic minerals. Akaganeite in Robert Sharp crater may have formed in acidic saline solutions through oxidative dissolution of Fe(II) sulfides and/or acidic oxidizing dissolution of basalts.

show abstract

Section: Resultsmentioning

confidence: 99%

Effect of Solution pH and Chloride Concentration on Akaganeite Precipitation: Implications for Akaganeite Formation on Mars

et al. 2018

View full text Add to dashboard Cite

show abstract

“…On the basis of weight loss, XRD data and quite similar variations of Cl/Fe ratio, the endothermic minimum at 230 8C should be attributed mainly to the loss of interstitial water instead of water removal from the tunnels, as has been suggested earlier [8,10,12]. According to determined Cl/Fe ratio (Table 4), the composition of b-FeOOH,Cl should be expressed by the formula FeOOHÁ0.163HClÁxH 2 O, where xH 2 O is the content of interstitial water [28], whereas the composition of the product after annealing at 230 8C is close to FeOOHÁ0.153HCl.…”

Section: Data From the Thermal And Edx Analysesmentioning

confidence: 93%

Peculiarities of heating-induced transformations in Fe(III) β-oxyhydroxides

Klimas

Mažeika

Pakštas

et al. 2015

Journal of Fluorine Chemistry

View full text Add to dashboard Cite

“…One of the most commonly employed manufacturing protocols for hematite involves crystallization from precursor akaganeite [ β -FeO(OH,Cl); space group I 2/ a ; Figure 2], which has a hollandite-like structure. In akaganeite, edge-linked octahedral chains form tunnels along (010) that are supported by Cl − or similarly sized anions, such as F − or OH − (Weiser and Milligan, 1935; Mackay, 1960; Chambaere and De Grave, 1984; Post and Buchwald, 1991; Cai et al ., 2001; Cornell and Schwertmann, 2003; Post et al ., 2003a). Based on a Rietveld analysis of powder X-ray diffraction data, Post and Buchwald (1991) report that Cl fills ~2/3 of the tunnel sites.…”

Section: Introductionmentioning

confidence: 99%

Evolution in the structure of akaganeite and hematite during hydrothermal growth: anin situsynchrotron X-ray diffraction analysis

2018

View full text Add to dashboard Cite

Synchrotron X-ray diffraction was used to monitor the hydrothermal precipitation of akaganeite (β-FeOOH) and its transformation to hematite (Fe2O3) in situ. Akaganeite was the first phase to form and hematite was the final phase in our experiments with temperatures between 150 and 200 °C. Akaganeite was the only phase that formed at 100 °C. Rietveld analyses revealed that the akaganeite unit-cell volume contracted until the onset of dissolution, and subsequently expanded. This reversal at the onset of dissolution was associated with a substantial and rapid increase in occupancy of the Cl site, perhaps by OH− or Fe3+. Rietveld analyses supported the incipient formation of an OH-rich, Fe-deficient hematite phase in experiments between 150 and 200 °C. The inferred H concentrations of the first crystals were consistent with “hydrohematite.” With continued crystal growth, the Fe occupancies increased. Contraction in both a- and c-axes signaled the loss of hydroxyl groups and formation of a nearly stoichiometric hematite.

show abstract

A study of the non-stoichiometrical halogen and water content of β-FeOOH

Cited by 26 publications

References 5 publications

Effect of Solution pH and Chloride Concentration on Akaganeite Precipitation: Implications for Akaganeite Formation on Mars

Effect of Solution pH and Chloride Concentration on Akaganeite Precipitation: Implications for Akaganeite Formation on Mars

Peculiarities of heating-induced transformations in Fe(III) β-oxyhydroxides

Evolution in the structure of akaganeite and hematite during hydrothermal growth: anin situsynchrotron X-ray diffraction analysis

Contact Info

Product

Resources

About