Characterization of mixed Fe-Al oxyhydroxides and oxides obtained by hydrothermal synthesis of nitrates, chlorides and urea as precursors

J. Bertoldi R. Marangoni L. Zatta About the authors

Abstract

Materials based on mixed aluminum and iron (III) and oxyhydroxides were prepared by the hydrothermal synthesis using urea, nitrates, or chlorides salts in different Al3+:Fe3+ molar ratios. The structural, morphological, and thermal properties of the materials were evaluated. The mixtures of Al3+ and Fe3+ nitrates led to the formation of hematite whereas, for the materials obtained from chlorides, different crystalline phases of Fe3+ were identified. For the thermal behavior, it was observed that, regardless of the anion of the precursors’ salts, the samples with composition 30%:70% (Al3+:Fe3+) stood out from the others. After calcination, the hematite phase was identified in all samples. The precursor salts and the Al3+:Fe3+ ratios reflected in differences between the samples in the evaluated properties. From the observed results, the occurrence of isomorphic substitutions of Fe3+ by Al3+ in the hematite phase was observed, which provided changes in the evaluated properties in relation to the material without the presence of Al3+.

Keywords:
hydrothermal synthesis; aluminum; iron; mixed oxyhydroxides; mixed oxides

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