Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

Shinoda, Kōzō; Tanno, Takenori; Fujita, Tetsuo; Suzuki, Shigeru

doi:10.2320/matertrans.m-m2009804

Cited by 31 publications

(20 citation statements)

References 29 publications

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“…The gel-like precursor is consumed and it is not observed in latter stage of scorodite formation. Shinoda et al 11) analyzed the chemical state of iron in the gel-like precursor by X-ray absorption near-edge structure (XANES) spectroscopy at the Fe K absorption edge. According to their results, the gel-like precursor mainly consists of Fe(II) with a small amount of Fe(III).…”

Section: Introductionmentioning

confidence: 99%

Scorodite Synthesis in As(V)-Containing Fe(II) Solution in the Presence of Hematite as a Fe(III) Source

2018

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Stabilization of arsenic by precipitation of large crystalline scorodite (FeAsO 4 •2H 2 O) particles is considered to be a promising option for treating As(V) contained in industrial by-products. In this study, scorodite synthesis by direct addition of hematite particles as a Fe(III) source to Fe(II) solution containing As(V) was investigated with different initial Fe(II) concentrations. During scorodite formation, the Fe(II) concentration and pH of the reaction solution are almost constant, and the residual arsenic concentration in the solution is low. The initial Fe(II) concentration strongly affects scorodite formation, and larger faceted crystalline scorodite particles are obtained with higher initial Fe(II) concentration. The observed scorodite particle size is larger than that formed by the conventional DMSP method. Coarse faceted scorodite can also be obtained by direct addition of hematite powder to FeSO 4 solution with As(V). From the results of environmental leaching tests, O 2 gas blowing for a short time to convert the remaining unstable gel-like precursor to crystalline scorodite is very effective to prevent arsenic leaching. Furthermore, for the gel-like precursor formed in the initial stage of the scorodite synthesis process, chemical state analysis by X-ray absorption spectroscopy in the range of the X-ray absorption near-edge structure at the Fe K absorption edge for iron reveals that the precursor contains Fe(II) as well as Fe(III). This indicates that scorodite does not directly form from Fe(III) ions from hematite and arsenate ions from solution, but a gel-like precursor initially forms from Fe(II) ions in solution and is then converted to crystalline scorodite.

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Section: Introductionmentioning

confidence: 99%

Scorodite Synthesis in As(V)-Containing Fe(II) Solution in the Presence of Hematite as a Fe(III) Source

2018

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“…Shinoda et al 23) used X-ray absorption near-edge structure spectroscopy to investigate the chemical state of Fe in the gel-like precursor. Their results showed that the precursor mainly consists of Fe(II) with a small amount of Fe(III).…”

Section: Introductionmentioning

confidence: 99%

Scorodite Crystal Formation on Hematite (Fe<sub>2</sub>O<sub>3</sub>) Surface in Fe(II) Solution Containing As(V)

2020

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Scorodite crystal formation on a hematite (Fe 2 O 3) surface in excess Fe(II) solution containing As(V) was observed under various conditions using the direct hematite addition method. Gel-like precursors initially formed and covered the entire hematite surface. Scorodite crystal nuclei then appeared preferentially on the grain boundaries of each hematite crystal, rather than on the flat hematite crystal surface. These grew into faceted crystalline scorodite particles through stepwise structure formation. The effects of solution temperature (50, 70, and 95°C), initial solution pH (0.6, 0.9, and 1.6), initial Fe(II) concentration (0, 25, and 55.9 g/L), and initial As concentration (25 and 50 g/L) on gel-like precursor and scorodite crystal formation were comprehensively investigated. The reaction temperature only affected the scorodite crystal formation rate and not the crystal shape in the studied range of 5095°C. Octahedral faceted scorodite was obtained at all temperatures studied. The solution pH strongly affected scorodite crystal formation, with a higher pH favoring scorodite formation in the studied range of pH 0.61.6. Scorodite crystals were not obtained at pH 0.6 because of the lower AsO 4 3¹ concentration in solution. Octahedral faceted scorodite crystals were also obtained at a lower Fe(II) concentration (25 g/L), but the gel-like precursor and scorodite crystals were not obtained in the absence of Fe(II). The As(V) concentration in solution affected the overall scorodite formation rate. Imperfect octahedral-shaped scorodite crystals with larger diameters were observed at lower As(V) concentration (25 g/L), which was attributed to the lower AsO 4 3¹ concentration. This study provides important information for As treatment through scorodite crystal formation using the hematite addition method.

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“…Scorodite (FeAsO 4 1 2H 2 O) is a promising material for the storage of concentrated arsenic generated by copper smelting. 1) Scorodite can be synthesized from a sulfuric acidic solution containing bivalent iron [Fe(II)] and pentavalent arsenic [As(V)] via oxidation under flowing O 2 gas.…”

Section: Introductionmentioning

confidence: 99%

“…4) Monitoring the growth process with scanning electron microscopy (SEM) revealed that the precursor agglomerated during the early stage of scorodite synthesis. 9,10) As reaction time increased, the agglomerates were transformed to scorodite by the crystal growth during further oxidation.…”

Section: Introductionmentioning

confidence: 99%

Utilization of carbon dioxide to synthesize large scorodite particles under ultrasound irradiation

Kitamura¹,

Okawa²,

Kato³

et al. 2018

Jpn. J. Appl. Phys.

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This study aims to synthesize large scorodite particles at 70 °C for 3 h via the oxidation of a precursor containing Fe(II) under flowing O2 gas by adding CO2 during ultrasound agglomeration process. First, the size of the precursor was increased with flowing O2 gas and stirring until the particle size was large enough to allow aggregation by 200 kHz ultrasound (1.1–2.9 µm). Next, the reaction solution was ultrasonically irradiated for 10 min under the flow of a mixed gas (O2 + CO2). Finally, the agglomerated precursor was oxidized under flowing O2 gas and stirring without ultrasound irradiation. The addition of a mixed gas containing 80 vol % O2 and 20 vol % CO2 and a short period (10 min) of ultrasound irradiation mitigated cavitation-related dispersion while preserving oxidation by O2 and oxidant radicals. Thus, the average size of synthesized particles was >10 µm from the laser diffraction particle size analysis.

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Coprecipitation of Large Scorodite Particles from Aqueous Fe(II) and As(V) Solution by Oxygen Injection

Cited by 31 publications

References 29 publications

Scorodite Synthesis in As(V)-Containing Fe(II) Solution in the Presence of Hematite as a Fe(III) Source

Scorodite Synthesis in As(V)-Containing Fe(II) Solution in the Presence of Hematite as a Fe(III) Source

Scorodite Crystal Formation on Hematite (Fe<sub>2</sub>O<sub>3</sub>) Surface in Fe(II) Solution Containing As(V)

Utilization of carbon dioxide to synthesize large scorodite particles under ultrasound irradiation

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