Thermal decomposition of barium ferrate(VI): Mechanism and formation of FeIV intermediate and nanocrystalline Fe2O3 and ferrite

Abstract

Simple high-valent iron-oxo species, ferrate(VI) (Fe VI O 2-4 , Fe(VI)) has applications in energy storage, organic synthesis, and water purification. Of the various salts of Fe(VI), barium ferrate(VI) (BaFeO 4) has also a great potential as a battery material. This paper presents the thermal decomposition of BaFeO 4 in static air and nitrogen atmosphere, monitored by combination of thermal analysis, Mössbauer spectroscopy, X-ray powder diffraction, and electron-microscopic techniques. The formation of Fe IV species in the form of BaFeO 3 was found to be the primary decomposition product of BaFeO 4 at temperature around 190 • C under both studied atmospheres. BaFeO 3 was unstable in air reacting with CO 2 to form barium carbonate and speromagnetic amorphous iron(III) oxide nanoparticles (< 5 nm). Above 600 • C, a solid state reaction between BaCO 3 and Fe 2 O 3 occurred, leading to the formation of barium ferrite nanoparticles, BaFe 2 O 4 (20-100 nm).

Effect of Synthesis Method on Antibacterial and Antibiofilm Activity Properties of BaFeO3-δ Perovskite Nanomaterials

“…Moreover, the existence of magnetic sextets in Mössbauer spectra indicated that the Néel temperature (T N ) of BaFeO 3 -Cop and BaFeO 3 -Sol samples is above the room temperature [29,30]. This result is agreement with previous reports for barium ferrate and Ba 1-x Ca x FeO 3 (where x=0.05) as well as it is consistent with the following magnetic measurement of the BaFeO 3 -Sol and BaFeO 3 -Cop samples [31,32]. The single peak and quadrupole doublet in the Mössbauer spectra of BaFeO 3 -Cop and BaFeO 3 -Sol samples (Fig.…”

Effect of Metal Ions on Oxidation of Micropollutants by Ferrate(VI): Enhancing Role of FeIV Species

“…Overall, the technique to identify directly Fe IV /Fe V species in the Fe VI –micropollutant systems under aqueous solutions remains elusive. However, the investigation of decomposition of solid Fe VI using Mossbauer spectroscopy has shown Fe IV as the intermediate species. , We have therefore applied a kinetic modeling approach to assess which of the two species, that is, Fe V and Fe IV , caused the enhancement.…”

“…However, the investigation of decomposition of solid Fe VI using Mossbauer spectroscopy has shown Fe IV as the intermediate species. 37,55 We have therefore applied a kinetic modeling approach to assess which of the two species, that is, Fe V and Fe IV , caused the enhancement.…”

“…Trace amounts of transition metal ions, such as Co­(II) and Ni­(II), could rapidly decompose Fe VI in water, which may produce large amounts of Fe IV /Fe V species in a short time, before being converted to Fe­(III) leading to an acceleration of oxidations by Fe VI . Formation of Fe IV /Fe V species has been seen in thermal decomposition of solid salts of Fe VI at 235 °C, , and formation of such iron intermediates may also occur under aqueous solution and room-temperature conditions. Furthermore, once the Fe IV /Fe V species are formed, their structures and properties would vary with the cations (or metal ions) present in solution-like synthesized salts of Fe VI having different metal ions. − The current study thus investigated for the first time the varying systems of enhanced oxidation of Fe VI in combination with different metal ions.…”

Reactive High-Valent Iron Intermediates in Enhancing Treatment of Water by Ferrate

“…The Mössbauer technique is suitable for solid samples and requires a certain amount of iron content in order to observe the spectrum of iron. Studies on ferrates using Mössbauer spectroscopy are largely limited to solid state chemistry. ,− Incorporation of 57 Fe into solid K 2 FeO 4 samples has been applied to minimize the required iron content for Mössbauer measurements. ,, Investigations on ferrates in solution require rapid freezing of the liquid to obtain solid samples prior to performing Mössbauer spectroscopy measurements (i.e., frozen solution) . In addition to the minimum iron content, the time required to freeze the liquid is another constraint that limits observations of the change in the iron oxidation state of ferrate during a short time scale.…”