Abstract
The microstructural and physical properties of magnetically separable CeO2 (5 wt.%)/Fe-oxide sorbents, applicable for the decomposition of organophosphorus pesticides, are analyzed in dependence on calcination temperature. The sorbents are prepared using a two-step procedure: (1) synthesis of magnetite core from cheap and commercially available raw materials; and (2) the formation of cerium (III) carbonate by precipitation with the ammonium hydrogen carbonate, containing re-dispersed magnetite. The cerous carbonate/magnetite precursor is annealed in a muffle furnace at temperatures ranging from 473 to 1073 K for 2 h to obtain the CeO2/Fe-oxide reactive sorbents. Structural characterization of the samples is performed using X-ray diffraction, scanning electron microscopy, Raman and Fourier transform infrared spectroscopy. Magnetic properties are obtained from hysteresis loops, field-cooled and zero-field-cooled curves, first-order reversal curve (FORC) diagrams, and Henkel plots. Sorbents exhibit an increase in coercivity from 0.2 kA/m to about 20 kA/m and a decrease in saturation magnetization from roughly 50 Am2/kg to 1 Am2/kg after annealing at 973 K. This deterioration of magnetic properties is caused by the transformation of magnetite and maghemite into weakly ferromagnetic hematite, with a typical peak in FORC diagram and a Morin transition at about 200 K. The degradation efficiency towards parathion and paraoxon methyl is about 30% for samples annealed from 473 K to 773 K.
Highlights
In recent years, cerium dioxide (CeO2) has been used in a variety of applications, either as a pure compound or as a part of various composites
Magnetic properties are obtained from hysteresis loops, field-cooled and zero-field-cooled curves, first-order reversal curve (FORC) diagrams, and Henkel plots
(2) SEM and energy-dispersive X-ray (EDX) analysis indicate that the sorbents contain a mix of grains of different sizes; some are enriched with Ce, and others are Ce depleted
Summary
Cerium dioxide (CeO2) has been used in a variety of applications, either as a pure compound or as a part of various composites. Developed a new kind of magnetically separable sorbent, formed from grains of iron oxide decorated by CeO2. Nanocrystallites was successfully applied in the decomposition of organophosphorus pesticides and chemical warfare agents. These investigations revealed that the degradation efficiency of sorbents depends on the CeO2 amount, and its crystallinity, which can be influenced by its method of preparation including calcination.. This paper discusses the preparation, microstructural, and physical characterization of magnetically separable CeO2(5 wt.%)/ Fe-oxide powder sorbents across a wide range of annealing temperatures (Ta) from 473 K to 1073 K. Further we demonstrate the sorbents degradation capabilities using selected pesticides Such a complex study of these composite materials has not yet been presented. The degradation efficiency towards parathion and paraoxon methyl exhibits a dependence on Ta
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