Iron(III) solubility and speciation in aqueous solutions. experimental study and modelling: part 1. hematite solubility from 60 to 300°C in NaOH–NaCl solutions and thermodynamic properties of Fe(OH)4−(aq)

Electroreduction of Iron(III) Oxide Pellets to Iron in Alkaline Media: A Typical Shrinking-Core Reaction Process

“…[16] [16] (DG°3 83K [110°C] < À36.49 kJ/mol). [48][49][50][51][52] In addition, a few small powdery electroreduction-generated iron grains are found in the reaction interface (the inset in Figure 14(a)), which suggests that the solid state electroreduction mechanism (Reactions [1] and [2]), i.e., Fe 2 O 3 fi Fe 3 O 4 fi Fe, is likely to present in the electroreduction process. The electroreduction-generated oxygen ion could then react with H 2 O to form OH À , i.e., O 2À + H 2 O fi 2OH À .…”

“…[15] The theoretical decomposition potentials (E°) for Reactions [1] through [3] have been calculated from the reported thermodynamic data. [48][49][50][51][52] …”

“…The standard Gibbs free energy changes (DG°) or the theoretical decomposition potentials (E°) for Reactions [4] through [9] have been calculated based on the reported thermodynamic data. [48][49][50][51][52] More details about the reaction mechanisms of the electrodeposition of iron from Fe 2 O 3 and NaFeO 2 precursors in aqueous NaOH solution can be found in our recent work. [56] Therefore, during the electroreduction process in this experiment, Fe 2 O 3 precursor and the electroreduction-generated Fe 3 O 4 and/or NaFeO 2 intermediates surrounded by aqueous NaOH solution would dissolve in the nearby electrolyte simultaneously, and then redeposit on the preformed iron to form dendritic crystals in the reaction front area immediately (as schematically shown in Figure 14(b)).…”

The electrolyte NRTL model and speciation approach as applied to multicomponent aqueous solutions of H2SO4, Fe2(SO4)3, MgSO4 and Al2(SO4)3 at 230–270°C

“…It is worthy to note that the ferric-hydroxo complexes Fe(OH) 2+ and Fe(OH) 2 + were included in the model. According to Diakonov et al [9], these species form as pH increases at room temperature. Since at high temperatures the pH of a sulphate solution also increases, one may assume that these hydroxide complexes also form.…”

“…The speciation of aluminum sulfate and magnesium sulfate in sulfuric acid solution are given by Baghalha and Papangelakis [2] as follows: The speciation of ferric sulfate in sulfuric acid solution at high temperature was given by Diakonov et al [9] and Liu et al [8]:…”