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Croatica Chemica Acta, Vol. 73 No. 2, 2000.

Original scientific paper

Forced Hydrolysis of Fe3+ Ions in NH4Fe(SO4)2 Solutions Containing Urotropin

Svetozar Musić ; Ruđer Bošković Institute, P. O. Box 180, HR-10002 Zagreb, Croatia
Ankica Šarić ; Ruđer Bošković Institute, P. O. Box 180, HR-10002 Zagreb, Croatia
Stanko Popović ; Ruđer Bošković Institute, P. O. Box 180, HR-10002 Zagreb, CroatiaDepartment of Physics, Faculty of Science, University of Zagreb, P. O. Box 331, HR-10002 Zagreb, Croatia
Kiyoshi Nomura ; School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113 Japan
Tsuguo Sawada ; School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113 Japan

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Abstract

The effects of urotropin on the hydrolysis of Fe3+ ions in NH4Fe(SO4)2 Solutions at 90 °C were investigated using X-ray powder diffraction, 57Fe Mössbauer spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Three concentrations of NH4Fe(SO4)2 Solutions, 0.03, 0.1 and 0.5 M, with varying initial amounts of urotropin were used in the experiments. Chemical and structural properties of the precipitates strongly depended on the concentrations of the reactants and the time of hydrolysis. In the early stages of Fe3+ hydrolysis, samples were dominantly amorphous. α-FeOOH, α-Fe2O3 and NH4Fe3(OH)6(SO4)2 were crystalline phases detected in the precipitates; however, the specific phase composition of each precipitate depended on the experimental conditions. The possible formation of schwertmannite was not proven in the precipitates. It was suggested that the particles of amorphous fraction, as well as α-FeOOH particles, contained significant amounts of sulphates on external and internal surfaces due to the specific adsorption. Regularity in the phase composition of the precipitates, as a function of the experimental conditions, was found. Crystallite sizes of oxides were estimated on the basis of the broadening of diffraction lines. Mossbauer spectroscopy indicated super-paramagnetic behavior of a-FeOOH particles. Formation of α-FeOOH particles of colloidal dimensions was proven by transmission electron microscopy.

Keywords

hydrolysis of Fe<sup>3+</sup>; NH<sub>4</sub>Fe(SO<sub>4</sub>)<sub>2</sub> Solutions; urotropin

Hrčak ID:

132070

URI

https://hrcak.srce.hr/132070

Publication date:

5.6.2000.

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