Abstract
Amorphous iron (III) oxide was obtained from clay, using ammonium hydroxide as a precipitating agent. Influence of freeze drying under vacuum, as a drying method, on particle size, chemical composition, and crystallinity of obtained iron (III) oxide powder was investigated. After freeze drying, precipitate was annealed in air at 500?C and 900?C. X-ray diffraction, particle size analysis, scanning electron microscopy, energy dispersive spectrometry, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis were used to characterize obtained iron (III) oxide powder. All of three powders obtained by freeze drying and annealing, have low crystallinity and particles with irregular layered shape. Narrow particle size distribution was given by an average diameter value of around 50 ?m for all observed powders. Iron-bearing materials like ?-Fe2O3 and ?- Fe2O3 are obtained. Differential thermal analysis curve of obtained samples showed endothermic reaction at 620?C which could be ascribed to phase transition from cubic form ?- ? ?- Fe2O3. Thermal transformations of iron (III) oxide, obtained from clay as a natural source, is suitable to explore in the framework of materials chemistry, and opens the possibility to synthesize materials based on Fe2O3 with specific magnetic behavior.
Highlights
European countries increasingly apply exploitation of accompanying minerals in coal mine deposits such as clay, sand, gravel, coal gangue, diatomaceous earth, fly ash, etc
Samples containing iron oxide particles were characterized at room temperature by Xray powder diffraction (XRD) by using Philips PW-1050 diffractometer with Ni-filtered CuKα radiation (1.54178 Å)
The XRD pattern of samples annealed at 500 oC, exhibited a remarkable broadening in 2θ region from 20-33o which is associated with the presence of amorphous silica
Summary
European countries increasingly apply exploitation of accompanying minerals in coal mine deposits such as clay, sand, gravel, coal gangue, diatomaceous earth, fly ash, etc. Iron (III) oxide is one of the ingredients of clay. Iron oxides are used for production of iron and steel, as pigments, catalysts, sensors, adsorbents, materials for magnetic data recording, etc. This work describes a possibility to obtain iron (III) oxide from clayey material as a raw material by co-precipitation method, and freeze dried under vacuum. This method does not require any specialized facilities. Clay as a source of iron (III) oxide was purified using thermal and chemical treatments before processing. Iron (III) oxide, was obtained from filtrate by precipitation method using ammonium hydroxide as a precipitation agent followed by decanting liquid phase. The powders were annealed in air (1 oC/min) at 500 oC and at 900 oC, for 6 h
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