Transformation of Solid Potassium Ferrate(VI) (K₂FeO₄): Mechanism and Kinetic Effect of Air Humidity

Abstract

The kinetics of solid-state transformation (aging) of potassium ferrate(VI) (K 2 FeO 4 ) under various air-humidity conditions (55-95 % relative humidity) at room temperature were studied by in-situ Mössbauer spectroscopy. The kinetic data showed a significant increase in the decomposition rate with increasing air humidity. The decomposition kinetics is very unusual with two almost linear decay steps. The first slow decay was observable at rather lower humidity levels (55-70 %) probably due to the formation of the narrow compact layer of nanoparticulate Fe(OH) 3 reaction product. This layer limits the access of both H 2 O and CO 2 participating in the reaction as the gaseous reactants. The second decay with much faster rate showed a nearly positive linear relationship with the humidity. The identification and characterization of the final products of aging were conducted by using X-ray

Mechanisms and Efficiency of the Simultaneous Removal of Metals and Cyanides by Using Ferrate(VI): Crucial Roles of Nanocrystalline Iron(III) Oxyhydroxides and Metal Carbonates

“…[39] It can thus be concluded that Ni remains in the reaction solution in the form of Ni II carbonate, as confirmed by the dimethylglyoxime method and IR absorption spectroscopy. Although this demonstrates that potassium ferrate(VI) effectively decomposes the K 2 [Ni (CN) 4 ], the resulting Ni II ions are almost exclusively preserved in the reaction solution due to the formation of highly soluble carbonate.…”

Ferryl and Ferrate Species: Mössbauer Spectroscopy Investigation

“…[25,26] The encapsulation of arsenic and heavy metals by iron(III) oxide nanoparticles (γ-Fe2O3), generated from Fe(VI), was investigated in detail by in-field Mössbauer spectroscopy. [27][28][29] In the case of arsenic, the results clearly demonstrated that a significant portion of arsenic was embedded in the tetrahedral sites of the γ-Fe2O3 spinel structure.…”

Preparation of Potassium Ferrate from Spent Steel Pickling Liquid

“…Figure 8 indicates that for a 32 h storage time, only 1.2% chemical reduction occurred to in-house potassium ferrate when stored under 35%-40% relative humidity (RH), while, if stored under the atmosphere of 67%-70% RH, Fe(VI) reduction rate to Fe(III) was 14.5%. Previous study elsewhere has observed an increase in Fe(VI) reduction with increasing RH at room temperature [28]. At a lower humidity (55%-70% RH), Fe(VI) decay was slow, while the decay rate was considerably enhanced at higher humidity such as 90%-95% RH [28].…”

“…At a lower humidity (55%-70% RH), Fe(VI) decay was slow, while the decay rate was considerably enhanced at higher humidity such as 90%-95% RH [28]. Formation of KHCO3 at higher RH was suggested to be an important reason for the enhanced Fe(VI) decay rate [28].…”