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Transformation of lepidocrocite

Fig. 14.12 The effect of silicate and seeding with goethite on the transformation of lepidocrocite to goethite in M KOH at 80 °C The figures on the curves give the Si concentration in mmol (Schwertmann Taylor, 1972 a with permission). Fig. 14.12 The effect of silicate and seeding with goethite on the transformation of lepidocrocite to goethite in M KOH at 80 °C The figures on the curves give the Si concentration in mmol (Schwertmann Taylor, 1972 a with permission).
Schwertmann, U. Taylor, R.M. (1972) The influence of silicate on the transformation of lepidocrocite to goethite. Clays Clay Min. 20 159-164... [Pg.625]

Gehring, A. U. and Hofmeister, A. M. (1994) The transformation of lepidocrocite during heating a magnetic and spectroscopic study. Clays Clay Min. 42 409-415. [Pg.169]

Fig. 6.10 Left Placement of various synthetic goethites (G), lepidocrocites (L) and hematites (H) in CIE L a b colour space. Right Development of a and b in the CIE L a b colour space during the transformation of ferrihydrite (common starting point) to goethite or hematite, respectively (Nagano et al., 1994, with permission). Fig. 6.10 Left Placement of various synthetic goethites (G), lepidocrocites (L) and hematites (H) in CIE L a b colour space. Right Development of a and b in the CIE L a b colour space during the transformation of ferrihydrite (common starting point) to goethite or hematite, respectively (Nagano et al., 1994, with permission).
With lepidocrocite the dehydroxylation endotherm due to transformation to maghemite is followed by an exotherm indicating transformation of maghemite to hematite. The temperature of the dehydroxylation endotherm was found to increase from 270 to 300 °C as A1 substitution rose from Al/(Fe-tAl) of 0 to 0.12 (Schwertmann Wolska, 1990) and that of the exotherm rose from 500 to 650 °C (Wolska et al., 1992). Synthetic feroxyhyte shows a weak dehydroxylation endotherm at ca. 260 °C (Carlson Schwertmann, 1980). [Pg.181]

The freshly precipitated Fe(OFI)2 sho ved broadened XRD lines and had a log of-14. With time a transformation to a more ordered phase vith log of-15.1 occurred. Figure 9.9 compares the solubility of Fe(OH)2 vith that of lepidocrocite as a function of pH. [Pg.220]

Bechine, K. Subrt, J. Hanslik,T. ZapletafV. Tlaskal, J. Lipka, J. Sedlak, B. Rotter, M. (1982) Transformation of synthetic y-FeOOH (lepidocrocite) in aqueous solutions of ferrous sulphate. Z. anorg. allg. Chem. 489 186-196... [Pg.559]

Cornell, R.M. Giovanoli, R. Schneider, W. (1989b) The transformation of ferrihydrite into lepidocrocite. Clay Min. 24 549-553 Cornell, R.M. Giovanoli, R. Schneider, W. [Pg.571]

The water molecules produced during mechanochemical dehydration of lepidocrocite facilitate the lithium mobility in a way similar to that found when LiOH melts and reacts with Fc20j. The structural transformation is explained within a model in which Li vacancies created during grinding promote the migration of Fe ions from octahedral to tetrahedral sites. [Pg.124]

Hydrothermal transformation of various Fe oxides. Ferrihydrite (2-line), lepidocrocite, akaganeite and goethite (if poorly crystalline) can be converted to large (1-3 am) hexagonal plates of hematite if kept under water in a teflon bomb at 180 °C for 10 days. [Pg.132]

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Lepidocrocite

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