Transformations from triclinic to hexagonal birnessite at circumneutral pH induced through pH control by common biological buffers

Ling, Florence T.; Heaney, Peter J.; Post, Jeffrey E.; Gao, Xiang

doi:10.1016/j.chemgeo.2015.10.007

Cited by 27 publications

(15 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One recent study, however, observed that TriB partially transforms to hexagonal H-birnessite at 573 pH 7 in solutions containing 20 mM MES or HEPES buffers and in unbuffered solutions after 14 574 days (Ling et al, 2015). This distinct outcome compared to the present study and prior research 575 Silvester et al, 1997;Lanson et al, 2000) is of unclear origin.…”

contrasting

confidence: 90%

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

Hinkle

Flynn

Catalano

2016

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

41 Naturally occurring Mn(IV/III) oxides are often formed through microbial Mn(II) 42 oxidation, resulting in reactive phyllomanganates with varying Mn(IV), Mn(III), and vacancy 43 contents. Residual aqueous Mn(II) may adsorb in the interlayer of phyllomanganates above 44 vacancies in their octahedral sheets. The potential for interlayer Mn(II)-layer Mn(IV) 45 comproportionation reactions and subsequent formation of structural Mn(III) suggests that 46 aqueous Mn(II) may cause phyllomanganate structural changes that alters mineral reactivity or 47 trace metal scavenging. Here we examine the effects of aging phyllomanganates with varying 48 initial vacancy and Mn(III) content in the presence and absence of dissolved Mn(II) at pH 4 and 49 7. Three phyllomanganates were studied: two exhibiting turbostratic layer stacking (δ-MnO 2 with 50 high vacancy content and hexagonal birnessite with both vacancies and Mn(III) substitutions) 51 and one with rotationally ordered layer stacking (triclinic birnessite containing predominantly 52 Mn(III) substitutions). Structural analyses suggest that during aging at pH 4, Mn(II) adsorbs 53 above vacancies and promotes the formation of phyllomanganates with rotationally ordered 54 sheets and mixed symmetries arranged into supercells, while structural Mn(III) undergoes 55 disproportionation. These structural changes at pH 4 correlate with reduced Mn(II) uptake onto 56 triclinic and hexagonal birnessite after 25 days relative to 48 hours of reaction, indicating that 57 phyllomanganate reactivity decreases upon aging with Mn(II), or that recrystallization processes 58 involving Mn(II) uptake occur over 25 days. At pH 7, Mn(II) adsorbs and causes limited 59 structural effects, primarily increasing sheet stacking in δ-MnO 2 . These results show that 60 aging-induced structural changes in phyllomanganates are affected by aqueous Mn(II)

show abstract

contrasting

confidence: 90%

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

Hinkle

Flynn

Catalano

2016

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

show abstract

“…1b). These differences in Mn valence states and vacancy concentrations are integral in establishing their stability with respect to pH and in predicting their chemical reactivity in natural environments (Ling et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Fourier-transform infrared spectroscopy (FTIR) analysis of triclinic and hexagonal birnessites

Ling

Post

Heaney

et al. 2017

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

Self Cite

View full text Add to dashboard Cite

The characterization of birnessite structures is particularly challenging for poorly crystalline materials of biogenic origin, and a determination of the relative concentrations of triclinic and hexagonal birnessite in a mixed assemblage has typically required synchrotron-based spectroscopy and diffraction approaches. In this study, Fourier-transform infrared spectroscopy (FTIR) is demonstrated to be capable of differentiating synthetic triclinic Na-birnessite and synthetic hexagonal H-birnessite. Furthermore, IR spectral deconvolution of peaks resulting from MnO lattice vibrations between 400 and 750cm yield results comparable to those obtained by linear combination fitting of synchrotron X-ray absorption fine structure (EXAFS) data when applied to known mixtures of triclinic and hexagonal birnessites. Density functional theory (DFT) calculations suggest that an infrared absorbance peak at ~1628cm may be related to OH vibrations near vacancy sites. The integrated intensity of this peak may show sensitivity to vacancy concentrations in the Mn octahedral sheet for different birnessites.

show abstract

“…It has been proposed that the primary buildup of Mn(III), which leads to passivation of the surface, results from the comproportionation reaction between Mn(II) product and surface Mn(IV) to produce Mn(III) [ 54 , 55 ]. This increase in Mn(III) is evidenced by the transformation of triclinic birnessite to hexagonal birnessite (Additional file 1 : Figure S6) [ 56 ], which is caused by migration of Mn(III) within the sheet to the interlayer region [ 39 ]. The oxidation of As(III) by surface Mn(III) is considered to be slow, consistent with the decreasing rate of As(V) formation as the reaction time increases [ 23 , 51 ].…”

Section: Resultsmentioning

confidence: 99%

Oxidation of arsenite to arsenate on birnessite in the presence of light

et al. 2016

View full text Add to dashboard Cite

The effect of simulated solar radiation on the oxidation of arsenite [As(III)] to arsenate [As(V)] on the layered manganese oxide, birnessite, was investigated. Experiments were conducted where birnessite suspensions, under both anoxic and oxic conditions, were irradiated with simulated solar radiation in the presence of As(III) at pH 5, 7, and 9. X-ray absorption spectroscopy (XAS) was used to determine the nature of the adsorbed product on the surface of the birnessite. The oxidation of As(III) in the presence of birnessite under simulated solar light irradiation occurred at a rate that was faster than in the absence of light at pH 5. At pH 7 and 9, As(V) production was significantly less than at pH 5 and the amount of As(V) production for a given reaction time was the same under dark and light conditions. The first order rate constant (kobs) for As(III) oxidation in the presence of light and in the dark at pH 5 were determined to be 0.07 and 0.04 h−1, respectively. The As(V) product was released into solution along with Mn(II), with the latter product resulting from the reduction of Mn(IV) and/or Mn(III) during the As(III) oxidation process. Post-reaction XAS analysis of As(III) exposed birnessite showed that arsenic was present on the surface as As(V). Experimental results also showed no evidence that reactive oxygen species played a role in the As(III) oxidation process.Electronic supplementary materialThe online version of this article (doi:10.1186/s12932-016-0037-5) contains supplementary material, which is available to authorized users.

show abstract

Transformations from triclinic to hexagonal birnessite at circumneutral pH induced through pH control by common biological buffers

Cited by 27 publications

References 58 publications

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

Structural response of phyllomanganates to wet aging and aqueous Mn(II)

Fourier-transform infrared spectroscopy (FTIR) analysis of triclinic and hexagonal birnessites

Oxidation of arsenite to arsenate on birnessite in the presence of light

Contact Info

Product

Resources

About