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Open AccessArticle

Tunable Mn Oxidation State and Redox Potential of Birnessite Coexisting with Aqueous Mn(II) in Mildly Acidic Environments

1
The Key Laboratory of Water and Sediment Sciences, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China
2
Beijing Key Laboratory of Mineral Environmental Function, Peking University, Beijing 100871, China
3
School of Water Resources and Environment, Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences Beijing, Ministry of Education, Beijing 100083, China
*
Authors to whom correspondence should be addressed.
Minerals 2020, 10(8), 690; https://doi.org/10.3390/min10080690
Received: 15 June 2020 / Revised: 28 July 2020 / Accepted: 30 July 2020 / Published: 2 August 2020
As the dominant manganese oxide mineral phase in terrestrial and aquatic environments, birnessite plays an important role in many biogeochemical processes. The coexistence of birnessite with aqueous Mn2+ is commonly found in the subsurface environments undergoing Mn redox cycling. This study investigates the change in Mn average oxidation state (AOS) of birnessite after reaction with 0.1–0.4 mM Mn2+ at pH 4.5–6.5, under conditions in which phase transformation of birnessite by Mn2+ was not detectable. The amount of Mn2+ uptake by birnessite and the equilibrium concentration of Mn(III) proportionally increased with the initial concentration of Mn2+. The Mn AOS of birnessite particles became 3.87, 3.75, 3.64, and 3.53, respectively, after reaction with 0.1, 0.2, 0.3, and 0.4 mM Mn2+ at pH 5.5. Oxidation potentials (Eh) of birnessite with different AOS values were estimated using the equilibrium concentrations of hydroquinone oxidized by the birnessite samples, indicating that Eh was linearly proportional to AOS. The oxidation kinetics of bisphenol A (BPA), a model organic pollutant, by birnessite suggest that the logarithms of surface area-normalized pseudo-first-order initial rate constants (log kSA) for BPA degradation by birnessite were linearly correlated with the Eh or AOS values of birnessite with AOS greater than 3.64. View Full-Text
Keywords: birnessite; Mn average oxidation state; redox potential; oxidative activity; removal of organic contaminants birnessite; Mn average oxidation state; redox potential; oxidative activity; removal of organic contaminants
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MDPI and ACS Style

Liu, J.; Zhang, Y.; Gu, Q.; Sheng, A.; Zhang, B. Tunable Mn Oxidation State and Redox Potential of Birnessite Coexisting with Aqueous Mn(II) in Mildly Acidic Environments. Minerals 2020, 10, 690. https://doi.org/10.3390/min10080690

AMA Style

Liu J, Zhang Y, Gu Q, Sheng A, Zhang B. Tunable Mn Oxidation State and Redox Potential of Birnessite Coexisting with Aqueous Mn(II) in Mildly Acidic Environments. Minerals. 2020; 10(8):690. https://doi.org/10.3390/min10080690

Chicago/Turabian Style

Liu, Juan; Zhang, Yixiao; Gu, Qian; Sheng, Anxu; Zhang, Baogang. 2020. "Tunable Mn Oxidation State and Redox Potential of Birnessite Coexisting with Aqueous Mn(II) in Mildly Acidic Environments" Minerals 10, no. 8: 690. https://doi.org/10.3390/min10080690

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