Original scientific paper

Investigation of Factors Influencing the Precipitation of Iron Oxides from Fe(II) Containing Solutions

Marijan Gotić ; Division of Materials Chemistry, Ruđer Bošković Institute, Zagreb, Croatia
Svetozar Musić ; Division of Materials Chemistry, Ruđer Bošković Institute, Zagreb, Croatia
Stanko Popović ; Department of Physics, Faculty of Natural Sciences and Mathematics, University of Zagreb, Zagreb, Croatia
Lavoslav Sekovanić ; Faculty of Geotechnical Engineering, University of Zagreb, Varaždin, Croatia

Abstract

Factors that influence the precipitation of iron oxides from Fe(II) containing solutions were investigated
by X-ray powder diffraction, 57Fe Mössbauer and FT-IR spectroscopies, FE SEM
and EDS techniques. Near spherical aggregates of spindle-shape goethite particles were obtained
by oxidation of 0.1 mol dm–3 FeSO4 solution (suspension) with pure oxygen at 90 °C.
Wide and thin goethite particles elongated along the crystallographic c-axis were formed in
parallel. With the addition of tetramethylammonium hydroxide to 0.1 mol dm–3 FeSO4 solution
(suspension) substoichiometric magnetite (Fe3-xO4) particles were additionally formed. They were
dominant at pH > 12.5. Mössbauer spectroscopy was used to calculate the stoichiometries of
Fe3-xO4 particles. Very small magnetite particles ( 20–100 nm) showed a tendency to aggregate.
The twinning effect of octahedral magnetite particles (> 200 nm) was observed. A drastic
effect on the properties of iron oxide precipitates was achieved by adding H3PO4 to the precipitation
system containing 0.1 mol dm–3 FeSO4 + 0.01 mol dm–3 H2SO4 solution at the start. In
dependence on the concentration of the added H3PO4, nanosize goethite particles about 15–25 nm
in size, or poor crystalline ferrihydrite particles (two-line ferrihydrite) were obtained. The EDS
analyses of the precipitates did not show any significant change in the sulphur content, whereas
the phosphorous content gradually increased in the precipitates with an increase in the added
H3PO4. In high concentrations phosphates completely suppressed the formation of goethite under
given experimental conditions, and phosphated ferrihydrite was formed instead.

Keywords

ferrihydrite; magnetite; phosphate; Mössbauer; FE SEM

Hrčak ID:

31182

URI

https://hrcak.srce.hr/31182

Publication date:

31.12.2008.

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