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7. Fe(II)-Catalyzed Recrystallization Drives Phosphorus and Aluminum Release from Goethite

Author

Karimian, Niloofar, Pownceby, Mark.I, Burton, Edward D., Wells, Martin, and Frierdich, Andrew J.

Abstract

Goethite often harbors impurities, such as phosphorus (P) and aluminum (Al), which are incorporated into its structure through direct substitution or coprecipitation with nanocrystalline phases. Understanding the processes that drive the release of P and Al from goethite is of paramount importance for the iron ore industry and for managing nutrient and pollutant behavior in the environment. This study investigates the impact of Fe(II)-catalyzed recrystallization on the release of P and Al from goethite. We evaluated the solubility and extractability of P and Al in suspensions of Al- and P-coprecipitated goethite, treated with 57Fe-enriched Fe(II)aqunder oxygen-free conditions for 30 days at neutral pH and room temperatures. The addition of Fe(II)aqinduced the recrystallization of goethite dominant initial synthetic phases (i.e., low P- and Al-containing phases) and the transformation of higher P- and/or Al-bearing starting material that was actually a mixture of goethite and minor amounts of lepidocrocite and feroxyhyte. Our results reveal that Fe(II)-catalyzed mineral and structural evolution led to the repartitioning of P and, to a lesser extent, Al throughout the crystal structure, mineral surface, and aqueous solution. Following a 30 day reaction with Fe(II)aq, we extracted approximately 80, 68.8, 73.9, and 83.2% of P from P-only, low, medium, and high P + Al goethite, respectively. Additionally, we observed total Al removals of approximately 17, 27, and 25% from low, medium, and high P + Al goethite, respectively. The results demonstrate that treating both P-only and P + Al goethite with Fe(II) at room temperature, followed by a 24 h extraction using 1 M NaOH, significantly enhances the overall extractability of P and Al, including both aqueous and surface-adsorbed fractions, compared to Fe(II)-free controls. These findings advance our understanding of the recrystallization process and impurity substitution in goethite, offering promising avenues for developing new environmentally friendly methods to extract P and other impurities from goethitic iron ores at lower temperatures.

Published
2024
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34. [Untitled]

Author

Karimian, Niloofar, Karimian, Niloofar, Karimian, Niloofar, and Karimian, Niloofar

Abstract

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35. Antimony and arsenic partitioning during Fe 2+ -induced transformation of jarosite under acidic conditions.

Author

Karimian N, Johnston SG, and Burton ED

Subjects
Arsenates, Ferrous Compounds chemistry, Hydrogen-Ion Concentration, Iron Compounds chemistry, Minerals chemistry, Mining, Oxidation-Reduction, Soil chemistry, Antimony chemistry, Arsenic chemistry, Ferric Compounds chemistry, Sulfates chemistry
Abstract

Jarosite [KFe 3 (SO 4 ) 2 (OH) 6 ] is considered a potent scavenger for arsenic (As) and antimony (Sb) under oxidizing conditions. Fluctuations in water levels in re-flooded acid sulfate soils (ASS) can lead to high Fe 2+ (aq) concentrations (∼10-20 mM) in the soil solution under acidic to circumneutral pH conditions. This may create favorable conditions for the Fe 2+ -induced transformation of jarosite. In this study, synthetic arsenate [As(V)]/antimonate [Sb(V)]-bearing jarosite was subjected to Fe 2+ (aq) (20 mM) at pH 4.0 and 5.5 for 24 h to simulate the pH and Fe 2+ (aq) conditions of re-flooded freshwater ASS/acid mine drainage (AMD)-affected environments at early and mid-stages of remediation, respectively. The addition of Fe 2+ at pH 5.5 resulted in the formation of a metastable green rust sulfate (GR- SO 4 ) phase within ∼60 min, which was replaced by goethite within 24 h. In contrast, at pH 4.0, jarosite underwent no significant mineralogical transformation. Although the addition of Fe 2+ (aq) induced the dissolution/transformation of jarosite at pH 5.5 and increased the mobility of Sb during the initial stages of the experiment (Sb (aq) = ∼0.05 μmol L -1 ), formation of metastable green rust (GR-SO 4 ) and subsequent transformation to goethite effectively sequestered dissolved Sb. Aqueous concentrations of As remained negligible in both pH treatments, with As being mostly repartitioned to the labile (∼10%) and poorly crystalline Fe(III)-associated phases (∼10-30%). The results imply that, under moderately acidic conditions (i.e. pH 5.5), reaction of Fe 2+ (aq) with jarosite can drive the dissolution of jarosite and increase Sb mobility prior to the formation of GR-SO 4 and goethite. In addition, repartitioning of As to the labile fractions at pH 5.5 may enhance the risk of its mobilisation during future mineral transformation processes in Fe 2+ -rich systems., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Published
2018
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