Solubility of hematite in LiOH, NaOH and KOH solutions

Ishikawa, Kanji; Yoshioka, Toshiaki; Sato, Tsugio; Okuwaki, Akitsugu

doi:10.1016/s0304-386x(96)00068-0

Cited by 37 publications

(24 citation statements)

References 5 publications

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“…Others works [7] have studied the solubility of hematite in alkaline solutions and proven that the solubility increases with temperature and the concentration of the alkali metal hydroxide, even though the solubility is still considered very low. The solubility of hematite changes signiicantly, depending on the nature of the alkali metal hydroxide (KOH < NaOH).…”

Section: Introductionmentioning

confidence: 99%

Comparing the deposition mechanisms in suspension plasma spray (SPS) and solution precursor plasma spray (SPPS) deposition of yttria-stabilised zirconia (YSZ)

Joulia

Bolelli

Gualtieri

et al. 2014

Journal of the European Ceramic Society

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Thermal spraying using liquid feedstock has emerged as a promising technology for the deposition of finely structured ceramic coatings. In order to provide a comparative assessment of the deposition mechanisms occurring when spraying suspension or solution feedstock, suspensions of 300 nm-sized ZrO2–4.5 mol.% Y2O3 particles dispersed in water and in ethanol and solutions of zirconium and yttrium salts, corresponding to ZrO2–4.5 mol.% Y2O3 and ZrO2–8 mol.% Y2O3 stoichiometries, were processed by plasma spraying using different parameter settings. In-flight diagnostics of sprayed droplets, together with the morphological, microstructural and phase analysis of individual lamellae collected onto polished substrates, performed by SEM, FIB, AFM and micro-Raman spectroscopy, led to the identification of deposition mechanisms, which were subsequently verified through the characterisation of complete coating layers

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Section: Introductionmentioning

confidence: 99%

Comparing the deposition mechanisms in suspension plasma spray (SPS) and solution precursor plasma spray (SPPS) deposition of yttria-stabilised zirconia (YSZ)

Joulia

Bolelli

Gualtieri

et al. 2014

Journal of the European Ceramic Society

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“…Actually, a trace amount of iron(III) oxide can dissolve in NaOH aqueous electrolyte in the form Fe(OH) 4 À , [14,15,54,55] the corresponding dissolution reaction is Fe 2 O 3 + 3H 2 O + 2OH À fi 2Fe(OH) 4 À . [15] Simultaneously, the intermediate product Fe 3 O 4 can also be dissolved in aqueous NaOH solution by the electroassisted dissolution Reaction [4].…”

Section: Solid State Electroreduction Mechanismmentioning

confidence: 99%

“…It was also suggested that the solubilities of iron species in aqueous NaOH solution generally increase with increasing temperature and NaOH concentration. [14,54] Therefore, in order to evaluate the possible electrodeposition routes during the electroreduction process, experiments were conducted to quantify the electrodeposition routes from the aqueous NaOH solutions saturated with Fe 2 O 3 and NaFeO 2 , respectively. The microstructures of the iron particles electrodeposited in Fe 2 O 3 -and NaFeO 2 -saturated 60 wt pct aqueous NaOH solutions at 383 K (110°C) and 1.7 V for 4 hours are shown in Figure 15.…”

Section: Solid State Electroreduction Mechanismmentioning

confidence: 99%

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

Zou

et al. 2015

Metall Mater Trans B

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Low temperature electrochemical reduction of iron(III) oxide to iron in a strongly alkaline solution has been systematically investigated in this article. The facile electrochemical process was carried out in 50 to 70 wt pct aqueous NaOH solution at 383 K (110°C) and 1.7 V. The preformed spherical Fe 2 O 3 pellets with porous structures were used directly as precursors for the electrolytic production of iron. The influences of the experimental parameters on the electroreduction process and the characteristics of the iron products as well as the reaction mechanisms were investigated. The results show that the precursor's pre-sintering process and the concentration of NaOH aqueous electrolyte have significant influences on the electroreduction process. The electroreduction-generated spherical metallic iron layer comprising dendritic iron crystals is first formed on the surface of Fe 2 O 3 pellet precursor and then extends gradually into the pellet's interior along the radial direction. The electroreduction process is confirmed to be a typical shrinking-core reaction process. The direct solid state electroreduction mechanism and the dissolution-electrodeposition mechanism coexist in the electrochemical process. The experimental observations suggest that the dissolution-electrodeposition mechanism appears to be the dominant mechanism under the experimental conditions employed in this study. This facile process may open a new green electricitybased route for the production of dendritic iron crystals from iron(III) oxide in alkaline media.

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“…As is the case for Al(OH) 3 , heating the alkaline sludge may increase solubilities of absorber compounds. For example, as shown in Figure 2 solution increases by a factor of two to three as the temperature is raised from 30° C to 76° C (Ishikawa et al (1997); data as a function of temperature at higher NaOH concentrations were not found in the technical literature). Although the Fe 2 O 3 solubility increase by heating occurs by approximately the same multiplicative factor as the solubility of Al(OH) 3 , the solubility of Fe 2 O 3 is only 10 -4 to 10 -3 M over the ~2 to 10 M NaOH and 30° C to 76° C range, much lower than the molar solubility of Al(OH) 3 .…”

Section: Op6 -Temperature Changesmentioning

confidence: 96%

Effects Influencing Plutonium-Absorber Interactions and Distributions in Routine and Upset Waste Treatment Plant Operations

Delegard

Sinkov

Fiskum

2015

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Permanganate Effects -The solubilities of (hydr)oxide compounds of aluminum, cadmium, chromium, iron, and uranium (but not manganese and nickel), and of plutonium itself, increase with alkaline concentration and thus help preserve the plutonium/absorber ratio in solution. However, the ratio may be altered in permanganate oxidative dissolution of discrete plutonium phases such as PuO 2 ,PuO 2 •xH 2 O, or other low-solubility tetravalent plutonium because of oxidation to more soluble pentavalent or hexavalent plutonium. The ratio also may be altered because of oxidative leaching of Cr(III) phases while compounds of other absorber elements (e.g., aluminum, iron, nickel) are largely redox-indifferent. Plutonium dissolution from genuine washed sludge with permanganate is significantly enhanced by an increase in NaOH concentration, increasing by an average factor of 70 when permanganate oxidative leaching is undertaken at 3 M NaOH as compared with 0.1 or 0.25 M NaOH. The increase is likely due to plutonium being more readily oxidized to the more soluble hexavalent state. Dissolved plutonium species in alkaline solution, irrespective of oxidation state, are anionic so they are not expected to sorb onto the cation-sorbing resin used for 137 Cs removal. Indeed, such sorption is observed to be negligible. Excess permanganate does not appear to have an appreciable effect on the distribution of plutonium to solution based on oxidative leaching of REDOX Process sludge simulants and genuine Cr(III)-bearing Hanford tank sludges. In lab testing, intentional over-dosage of permanganate did not lead to enhanced plutonium leaching at lower alkalinity (0.09 to 0.25 M NaOH), while at higher alkalinity (3 M NaOH), the plutonium concentration increase to ~0.00036 g Pu/L was relatively low and could be mitigated by adding Cr(III) nitrate to the permanganate/manganate-bearing slurry to eliminate excess oxidant, form MnO 2 , and remove ~95% of the solubilized plutonium by coprecipitation. Separate testing showed that plutonium dissolution in the presence of excess permanganate at 2 to 4 M NaOH also can be mitigated by addition of hydrogen peroxide, removing ~75% of the solubilized plutonium. In treatment with Sr/Mn(VII) for 90 Sr and transuranic element removal from Envelope C supernates, both coprecipitated plutonium that remains undissolved and the residual soluble plutonium, should be protected with 100 to 1000 times higher neutron absorber concentrations based on AN-102 supernate studies. Although experimental data on 239 Pu decontamination from AN-107 supernates are lacking, it is likely that plutonium decontamination by Sr/Mn(VII) treatment was similar to that of AN-102 supernates based on solution composition and total alpha analyses. Decontamination of tank SY-101 from dissolved plutonium by permanganate treatment also is found. Overall, treatment of Envelope C wastes by Sr/Mn(VII) should improve criticality safety by carrying plutonium into the solid phase in the presence of co-precipitated iron and especially manganese.Cerium an...

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Solubility of hematite in LiOH, NaOH and KOH solutions

Cited by 37 publications

References 5 publications

Comparing the deposition mechanisms in suspension plasma spray (SPS) and solution precursor plasma spray (SPPS) deposition of yttria-stabilised zirconia (YSZ)

Comparing the deposition mechanisms in suspension plasma spray (SPS) and solution precursor plasma spray (SPPS) deposition of yttria-stabilised zirconia (YSZ)

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

Effects Influencing Plutonium-Absorber Interactions and Distributions in Routine and Upset Waste Treatment Plant Operations

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