Original scientific paper

Influence of Urotropin on the Precipitation of Iron Oxides from FeCl₃ Solutions

Ankica Šarić ; Ruđer Bošković Institute, P. O. Box 1016, 10001 Zagreb, Croatia
Svetozar Musić ; Ruđer Bošković Institute, P. O. Box 1016, 10001 Zagreb, Croatia
Kiyoshi Nomura ; School of Engineering, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113 Japan
Stanko Popović ; Department of Physics, Faculty of Science, University of Zagreb, P. O. Box 162, 10001 Zagreb, Croatia

Abstract

Precipitations of iron oxides from FeCl₃ solutions in the presence of urotropin at 90 °C were monitored using the Fourier transform infrared spectroscopy, Mössbauer spectroscopy, X-ray diffraction and transmission electron microscopy. Urotropin was used as a generator of OH- ions. The precipitation processes depended on the concentrations of FeCl₃ and urotropin and the time of aging. After 1 day of aging the precipitation systems up to pH ≈ 2, the β-FeOOH phase was precipitated, while in the region of 5 < pH < 6 the mixtures of β-FeOOH, α-Fe₂O₃ and α-FeOOH were precipitated, and at pH > 6 the mixtures of α-Fe₂O₃ and α-FeOOH were observed. The β-FeOOH phase precipitated at 2.16 < pH < 5.55 dissolved after 7 days, yielding soluble iron for the α-FeOOH growth on account of α-Fe₂O₃. At pH ≈ 1.5 and less, β-FeOOH was present as a single phase up to 7 days of aging the precipitation systems. The mechanisms of iron oxide precipitation in dependence on pH were discussed. The size and morphology of oxide particles were strongly influenced by experimental conditions of the precipitation process as shown by transmission electron microscopy.

Keywords

Hrčak ID:

132435

URI

https://hrcak.srce.hr/132435

Publication date:

1.12.1998.

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