Redox Reactions between Mn(II) and Hexagonal Birnessite Change Its Layer Symmetry

Zhao, Hongbin; Zhu, Mengqiang; Li, Wei; Elzinga, Evert J.; Villalobos, Mario; Fan, Louzhen; Zhang, Jing; Feng, Xionghan; Sparks, Donald L.

doi:10.1021/acs.est.5b04436

Cited by 111 publications

(121 citation statements)

References 57 publications

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“…Such an evolution was consistent with previous studies (Elzinga, 2011(Elzinga, , 2016Lefkowitz et al, 2013;Lefkowitz & Elzinga, 2015). In the following section, the mechanisms of transformation were studied at the crystal scale, hypothesizing that an increased concentration of Mn 2þ led to an increased conversion of d-MnO 2 to synthetic feitknechtite without significant dissolution of d-MnO 2 .…”

Section: Mineralogical Evolutionsupporting

confidence: 87%

“…The present description of the vernadite-to-feitknechtite transformation, from macroscopic to crystal scales, is consistent with our current understanding of this transformation (Elzinga, 2011(Elzinga, , 2016Lefkowitz et al, 2013;Lefkowitz & Elzinga, 2015). One of the key findings is the major role of oriented aggregation in the nucleation and growth of feitknechtite from d-MnO 2 precursors.…”

Section: The Role Of Oriented Aggregation In Nanoparticle Growthsupporting

confidence: 87%

“…The 2Mn 3þ (s) formed may further disproportionate, returning the system to its initial state. Alternatively, they may accumulate in the structure and induce a change in layer symmetry, from hexagonal to orthogonal, as observed experimentally at pH 9 when the molar ratio of Mn 2þ to d-MnO 2 is lower than 0.05 (Zhao et al, 2016). At lower pH and/or at higher Mn 2þ concentration, a transformation to synthetic feitknechtite (b-MnOOH) is observed, following the reaction:…”

Section: Mn 2þmentioning

confidence: 81%

“…The possible contact with redox-sensitive species such as Mn 2þ can induce structural changes whose nature and extent depend on solution pH and Mn 2þ concentration. The first step of reaction between aqueous Mn 2þ and layer Mn 4þ , hereafter referred to as Mn 2þ (aq) and Mn 4þ (s) , respectively, is (Elzinga, 2016):…”

Section: Introductionmentioning

confidence: 99%

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Nucleation and growth of feitknechtite from nanocrystalline vernadite precursor

Grangeon¹,

Warmont²,

Tournassat³

et al. 2017

ejm

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Vernadite is a nanocrystalline manganese oxide, which controls the fate of many trace elements in soils and sediments through sorption and oxidative-degradation mechanisms. This exceptional reactivity directly results from its crystal structure, which may however evolve upon contact with redox-sensitive species. Understanding these changes is a prerequisite to predict and model the geochemical cycle of trace elements in the environment. Here, the structural and morphological modifications affecting synthetic nanocrystalline vernadite (d-MnO 2 ) upon contact with increasing concentrations of Mn 2þ were investigated using wet chemistry, synchrotron X-ray diffraction and transmission electron microscopy. Fresh d-MnO 2 crystals had an Mn oxidation state of 3.94 ± 0.05 and a ∼10 A layer-to-layer distance. Crystal size was ∼10 nm in the layer plane, and ∼1 nm perpendicular to that. Upon contact with aqueous Mn 2þ under anoxic conditions, d-MnO 2 crystals underwent several morphological and mineral evolutions, starting with the stacking, perpendicular to the layer plane, of d-MnO 2 crystals to form crystals ∼10 nm Â 2 nm which were then subjected to oriented aggregation both along and perpendicular to the layer plane to form lath-like crystals with dimensions of ∼100 nm Â 20 nm. Finally, these laths stacked perpendicular to the layer plane to form synthetic feitknechtite (b-MnOOH) crystals with sizes up to ∼100 nm Â 500 nm when the Mn 2þ loading reached 31.9 mmol g À1 . Structural transformation from d-MnO 2 to synthetic feitknechtite was detected at Mn 2þ loading equal to or higher than 3.27 mmol g À1 . These mechanisms are likely to influence the geochemical fate of trace elements in natural settings where Mn 2þ is abundant. Firstly, the systematic increase in crystal size with increasing Mn 2þ loading may impact the sorption capacity of vernadite and feitknechtite by reducing the density of reactive edge sites. Secondly, the fate of trace elements initially sorbed at the vernadite surface is unclear, as they could either be released in solution or incorporated into the feitknechtite lattice.

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Section: Mineralogical Evolutionsupporting

confidence: 87%

Section: The Role Of Oriented Aggregation In Nanoparticle Growthsupporting

confidence: 87%

Section: Mn 2þmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Nucleation and growth of feitknechtite from nanocrystalline vernadite precursor

Grangeon¹,

Warmont²,

Tournassat³

et al. 2017

ejm

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“…44 In addition, previous reports have shown that Mn(II) can react with birnessite and alter the XRD pattern of the birnessite. 43,47,48 In our case, we found that the XRD patterns of the birnessite before and after reaction with Gb1 are essentially identical (see SI), further indicating that little Mn(II) is produced during the reaction. Therefore, we propose that degradation of Gb1 by birnessite is the result of hydrolysis of the peptide bond catalyzed by the birnessite surface.…”

Section: Articlesupporting

confidence: 53%

Abiotic Protein Fragmentation by Manganese Oxide: Implications for a Mechanism to Supply Soil Biota with Oligopeptides

Reardon

Chacon

Walter

et al. 2016

Environ. Sci. Technol.

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The ability of plants and microorganisms to take up organic nitrogen in the form of free amino acids and oligopeptides has received increasing attention over the last two decades, yet the mechanisms for the formation of such compounds in soil environments remain poorly understood. We used Nuclear Magnetic Resonance (NMR) and Electron Paramagnetic Resonance (EPR) spectroscopies to distinguish the reaction of a model protein with a pedogenic oxide (Birnessite, MnO2) from its response to a phyllosilicate (Kaolinite). Our data demonstrate that birnessite fragments the model protein while kaolinite does not, resulting in soluble peptides that would be available to soil biota and confirming the existence of an abiotic pathway for the formation of organic nitrogen compounds for direct uptake by plants and microorganisms. The absence of reduced Mn(II) in the solution suggests that birnessite acts as a catalyst rather than an oxidant in this reaction. NMR and EPR spectroscopies are shown to be valuable tools to observe these reactions and capture the extent of protein transformation together with the extent of mineral response.

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