Fe-57 Mossbauer, FT-IR and TEM observations of oxide phases precipitated from concentrated Fe(NO3)(3) solutions

Musić, Svetozar; Santana, Genilson P.; Šmit, Goran; Garg, Vijayendra K. (1999) Fe-57 Mossbauer, FT-IR and TEM observations of oxide phases precipitated from concentrated Fe(NO3)(3) solutions. Croatica Chemica Acta, 72 (1). pp. 87-102. ISSN 0011-1643

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Abstract

Concentrated Fe(NO3)(3) solutions (final Fe3+ concentration of 1 M) were completely or partially neutralized by addition of concentrated NaOH solution, and then aged at various temperatures and times. The oxide phases were investigated using Mossbauer spectroscopy, FT-IR spectroscopy and transmission electron microscopy. In a highly alkaline medium, single phase alpha-FeO(OH) was obtained by the aging of Fe(OH)(3) suspension at room temperature (RT) for 135 days. The Mossbauer spectrum of this sample at 298 K showed superposition of the central quadrupole doublet and a collapsing sextet, while at 80 K a sextet corresponding to alpha-FeO(OH) was recorded. In the highly alkaline medium, an amorphous material was obtained after heating the Fe(OH)(3) suspension at 333 K for 1 day. Spectroscopic investigations provided a certain evidence of the presence of alpha-Fe2O3 in this material. With prolonged time of heating, alpha-FeO(OH) appeared at 333 K and its fraction showed a tendency to increase. It was suggested that, in a highly alkaline medium, nucleation and crystallization of alpha-Fe2O3 occurred inside the amorphous gel, while alpha-FeOOH crystallized by a dissolution/reprecipitation mechanism. After neutralization of 90% of 1 M Fe(NO3)(3) solution, lemon-shaped alpha-Fe2O3 particles were produced at 398 K between 6 and 24 h. Interpretations of the spectroscopic and electron microscopic measurements are given.

Item Type:

Article

Uncontrolled Keywords:

x-ray-diffraction; feso4 solution; structural-properties; beta-feooh; fe3+ ions; hydrolysis; spectroscopy; particles; hematite; ferrihydrite

Subjects:

NATURAL SCIENCES > Chemistry

Divisions:

Division of Materials Chemistry

Projects: