Hydroxide, ferric amorphous

Am. Ceram. Soc. 51 594-599 Okamoto, S. Sekizawa, H. Okamoto, S.I. (1972) Characterization and phase transformation of amorphous ferric hydroxide. In Anderson, J.S. Roberts, M.W. Stone, F.S. (eds.) Proc. 7 Int. Symp. on Reactivity of Solids, Chapman Hall, London, 341-349 Oles, A., Szytula, A. Wanic, A. (1970) Neutron diffraction study of y-FeOOH. Phys. Stat. Sol. 41 173-177... 

Schwertmann, U. Fischer, W.R. (1973) Natural amorphous ferric hydroxide. Geoderma 10 237-247... 

Schwertmann, U. (1964) DifFerenzierung der Eisenoxide des Boden durch Extraktion mit Ammoniumoxalat-Ldsung. Z. Pflanzener-nahr. Diing. Bodenk. 105 194-202 Schwertmann, U. (1966) Inhibitory effect of soil organic matter on the crystallization of amorphous ferric hydroxide. Nature 212 645-646 Schwertmann, U. (1971) Transformation of hematite to goethite in soils. Nature 232 624-625... 

In this case study, the selected phases are pyrite, amorphous FeS, calcite (present in limestones in the roof strata Fig. 5), dolomite (possibly also present in the limestones), siderite (which occurs as nodules in roof-strata mudstones), ankerite (present on coal cleats in the Shilbottle Seam), melanterite and potassium-jarosite (representing the hydroxysulphate minerals see Table 3), amorphous ferric hydroxide (i.e., the ochre commonly observed in these workings, forming by precipitation from ferruginous mine waters), and gypsum (a mineral known to precipitate subaqueously from mine waters with SO4 contents in excess of about 2500 mg/L at ambient groundwater temperatures in this region, and with which most of the mine waters in the district are known to be in equilibrium). In addition, sorption reactions were included in some of the simulations, to contribute to the mole transfer balances for Ca, Na, and Fe. 

Schwertmann, U. 1966. Inhibitory effect of soil organic matter on the crystallization of amorphous ferric hydroxide. Nature 212 645-646. 

Amorphous hydroxide Fe(0H)3.nH20 Amorphous ferric hydroxide... 

Amorphous ferric hydroxide. Most of Spring Creek below the Boulder Creek confluence is iron stained and actively precipitates iron hydroxide. 

Figure 7. Saturation indices for amorphous ferric hydroxide plotted as a function of the log conductivity showing an approach to saturation for the more dilute and more oxidized downstream waters...

Figure 10.7 Adsorption isotherm describing the adsorption of uranyl (UO +) species onto suspended amorphous ferric hydroxide at pH 7.23 and 25°C. The vertical line denoting saturation with respect to schoepite [U02(0H)2 H2OI has been computed from the pH and dissolved uranyl concentration. The enrichment factor, E.F., equals K,. Reprinted from Geochim. et Cosmochim. Acta, Vol. 53(6), D. Langmuir, Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits, pp. 547-569,...

Ferrihydrite, [5Fe203 9H2O], once called "amorphous ferric hydroxide", has been reported in bog iron and drainage ditches and in environments where other compounds prevent the formation of goethite and lepidocrocite (Schwertmann, 1988). It occurs as bulky precipitates containing water, adsorbed ions, and organic material. It appears as small (5.0-10.0 nm), spherical particles with a high surface area (200-350 m /g Schwertmann and Taylor, 1977). Ferrihydrite is probably the form of iron present in the B horizon of true Podzols. 

Thus, the rates of precipitation and "aging" of ferric oxyhydroxide solids are evident from each of our experiments. In all cases, solid is indicated at the first data point, and the pQ of the solid increases and levels off over a period of time depending upon the conditions. In 31 separate experiments, spanning the entire range of iron concentrations listed above, the average "final" value for pQ is 38.3 +/- 0.4. (All uncertainties expressed here and subsequently are +/- one standard deviation). As discussed above, these pQ values probably correspond to a mixture of amorphous ferric hydroxide and akagancite present 12-200 hours after initial precipitation. 

In the case of the Fe(III)-H20 system, the initial precipitation product is an amorphous ferric hydroxide, Fe(OH)3(s). It has been postulated by van der Woude and de Bruyn [35] that the formation of the corresponding supercritical nucleus may be viewed in terms of the reaction... 

F. Esmadi, J. Simm, Sorption of cobalt(II) by amorphous ferric hydroxide . Colloids and Surfaces A Physicochemical and Engineering Aspects, 104 (2/3) (1995), pp. 265-270. 

A solution of ferritin mixed with sodium hydroxide gives rise to a brown precipitate of ferric hydroxide, which is not precisely of the composition FeOOH, but contains some phosphate, just as all amorphous ferric hydroxides, especially those obtained from coagulation of any colloidal ferric hydroxide sol, contains some anionic constituents other than OH. The phosphorus content of that precipitate is smaller than would correspond to the ratio 1 9 mentioned above. A part of the phosphate seems to be split off from its attachment to iron, when the iron is precipitated by sodium hydroxide. 

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