Effect of ionic strength on the kinetics of oxidation of ferrous ion by chlorate ion

Ang, K. P.; Creak, G. Alan; Kwik, W.L.

doi:10.1039/dt9720002560

Cited by 6 publications

(10 citation statements)

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“…A kinetic rate law model for dissolved Fe(II) oxidation by chlorate [63][64][65] was previously implemented in The Geochemist's Workbench module React [49], using a modified LLNL database [86,87]. This kinetic model was employed in the present study to simulate the reaction of chlorate with Fe(II), using the starting compositions of the experiments.…”

Section: Kinetic Experimentsmentioning

confidence: 99%

“…To further evaluate the stoichiometric efficiency of chlorate, the kinetic data were compared to the predictions of the rate model from Mitra and Catalano [49], which followed the following rate law [63][64][65] (2)…”

Section: Iron Oxidation Inmentioning

confidence: 99%

“…Geochemically similar systems can produce different mineral products due to the differences in their iron oxidation rate (Figure 3). The oxidation rate is primarily controlled by the reactant concentration ([Fe(II)] and [ClO 3 − ]) (Equation ( 2)) [63][64][65], with dilute solutions experiencing slower oxidation rate than solutions with higher concentrations. Chloride-rich, "Chlorate-excess" ([…”

Section: Oxidation Ratementioning

confidence: 99%

“…While chlorate likely always co-occurs with perchlorate, the latter displays no reactivity towards Fe(II) [49,61,62] and is not relevant to iron chemistry on the Martian surface. Fe(II) oxidation by ClO 3 − is represented by the following net redox reaction [63][64][65]:…”

Section: Introductionmentioning

confidence: 99%

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Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars

Mitra¹,

Moreland²,

Catalano³

2020

Minerals

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Chlorate is an important Cl-bearing species and a strong potential Fe(II) oxidant on Mars. Since the amount of oxychlorine species (perchlorate and chlorate) detected on Mars is limited (<~1 wt.%), the effectiveness of chlorate to produce iron oxides depends heavily on its oxidizing capacity. Decomposition of chlorate or intermediates produced during its reduction, before reaction with Fe(II) would decrease its effective capacity as an oxidant. We thus evaluated the capacity of chlorate to produce Fe(III) minerals in Mars-relevant fluids, via oxidation of dissolved Fe(II). Each chlorate ion can oxidize 6 Fe(II) ions under all conditions investigated. Mass balance demonstrated that 1 wt.% chlorate (as ClO3−) could produce approximately 6 to 12 wt.% Fe(III) or mixed valent mineral products, with the amount varying with the formula of the precipitating phase. The mineral products are primarily determined by the fluid type (chloride- or sulfate-rich), the solution pH, and the rate of Fe(II) oxidation. The pH at the time of initial mineral nucleation and the amount of residual dissolved Fe(II) in the system exert important additional controls on the final mineralogy. Subsequent diagenetic transformation of these phases would yield 5.7 wt.% hematite per wt.% of chlorate reacted, providing a quantitative constraint on the capacity of chlorate to generate iron oxides on Mars.

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Section: Kinetic Experimentsmentioning

confidence: 99%

Section: Iron Oxidation Inmentioning

confidence: 99%

Section: Oxidation Ratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars

Mitra¹,

Moreland²,

Catalano³

2020

Minerals

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“…Kinetic geochemical modeling of Fe(II) oxidation by chlorate was done using the kinetic rate law model ,, that was previously implemented in The Geochemist’s Workbench module React , using a modified LLNL database. , This kinetic model was employed to simulate the reaction of chlorate with Fe(II), using the temperatures and starting compositions of the experiments. Details of the kinetic model, rate constants, and the activation energy can be found in our previous paper …”

Section: Methodsmentioning

confidence: 99%

Rates and Products of Iron Oxidation by Chlorate at Low Temperatures (0 to 25 °C) and Implications for Mars Geochemistry

Mitra

Moreland

Knight

et al. 2022

ACS Earth Space Chem.

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The mean annual surface temperatures on present and early Mars likely remain well below 0 °C with episodic warming to temperatures as high as 20 °C. Temperature exerts a strong control on geochemical processes but fundamental phenomena like iron oxidation and the formation of iron oxides have not been widely studied below 20 to 25 °C. Earlier studies have demonstrated the effectiveness of chlorate in oxidizing dissolved Fe(II) to form Fe(III)-bearing minerals commonly found on Mars. Here, we determined the rate of oxidation of dissolved ferrous iron by chlorate and the resulting formation of mineral precipitates as a function of temperature in Mars-relevant fluids. The results demonstrate that chlorate oxidizes dissolved Fe(II) at temperatures as low as 0 °C on the time scale of weeks to months. Mixtures of different Fe(III) phases, including goethite, lepidocrocite, schwertmannite, and akaganeite, were produced and the minerals formed were found to be primarily dependent on the fluid type, pH, concentration, and temperature. Chloride-rich solutions favored the formation of akaganeite at 4 °C while 24 °C solutions favored lepidocrocite. In both chloride- and sulfate-rich solutions, lepidocrocite formation was favored at 4 °C whereas 24 °C fluids preferably produced goethite. Schwertmannite formed in sulfate-rich solutions that started at low pH. An established kinetic rate law model parametrized at higher temperatures was found to be accurate in determining the rate of Fe(II) oxidation at temperatures as low as 0 °C. Rate comparisons of Fe(II) oxidation showed that in an ∼1 mmol L–1 chlorate solution at 0 °C the rate is about three times faster than under 1 bar oxygen at 25 °C, demonstrating the effectiveness of chlorate as an important Fe(II) oxidant on Mars. The impact of temperature in determining the Fe(III) oxidation products suggests that iron mineralogy in cryogenic systems on Mars may be distinct from the phases forming in more clement terrestrial analog environments.

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ChemInform Abstract: EINFLUSS DER IONENSTAERKE AUF DIE OX.‐KINETIK DES EISEN(II)‐IONS DURCH DAS CHLORATION

Ang¹,

Creak²,

Kwik³

1973

Chemischer Informationsdienst

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Effect of ionic strength on the kinetics of oxidation of ferrous ion by chlorate ion

Cited by 6 publications

References 0 publications

Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars

Capacity of Chlorate to Oxidize Ferrous Iron: Implications for Iron Oxide Formation on Mars

Rates and Products of Iron Oxidation by Chlorate at Low Temperatures (0 to 25 °C) and Implications for Mars Geochemistry

ChemInform Abstract: EINFLUSS DER IONENSTAERKE AUF DIE OX.‐KINETIK DES EISEN(II)‐IONS DURCH DAS CHLORATION

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