Naslov
Chemical and microstructural properties of oxide phases obtained by forced hydrolysis of Fe3+ ions

Autori
Musić, Svetozar ; Šarić, Ankica ; Nomura, Kiyoshi ; Popović, Stanko

Izvornik
Ach : models in chemistry (1217-8969) 136 (1999), 4; 457-476

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
hydrolysis ; Fe3+ ions

Sažetak
The chemical and microstructural properties of oxide phases obtained by forced hydrolysis of Fe ions at 90°C, were investigated using X-ray powder diffraction, Fourier transform infrared spectroscopy, 57Fe Mössbauer spectroscopy and transmission electron microscopy. Urotropin (hexamethylenetetramine) was used as a generator of OH ions. After 5 hours of the hydrolysis of 0.1 M Fe(NO3)3 solution in an acidic medium the RT Mössbauer spectrum showed a broad size distribution of a-FeOOH particles, while XRD showed the presence of an amorphous fraction and a-FeOOH. With a prolonged heating time a-FeOOH was transformed to a-Fe2O3 by a dissolution/reprecipitation mechanism. At the beginning of precipitation process the amorphous fraction increased with an increase of urotropin concentration and for 0.25 M urotropin the sample was completely amorphous, as shown by XRD. For the same sample RT Mössbauer spectrum showed a quadrupole doublet. After 3 and 5 hours of aging of the precipitation system in the presence of 0.1 M urotropin, traces of a-FeOOH were observed in the FT-IR spectra, while for 0.25 M urotropin FT- IR spectroscopy did not show any a-FeOOH content. For longer ageing times (7 and 21 days) of the precipitation systems mixtures of a-Fe2O3 and a- FeOOH were found and tendency of the a-FeOOH fraction to increase with an increase in the urotropin concentration was observed. A possible mechanism of crystallization of a-Fe2O3 and a- FeOOH from an amorphous phase in the near neutral pH region is discussed. The size and morphology of oxide particles depended strongly on the experimental conditions of their formation.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA