Rapid determination of the Mn average oxidation state of Mn oxides with a novel two-step colorimetric method

Zhu, Yanhua; Liang, Xinran; Zhao, Hongbin; Yin, Hui; Liu, Mingming; Liu, Fan; Feng, Xionghan

doi:10.1039/c6ay02472f

Cited by 44 publications

(19 citation statements)

References 33 publications

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“…S2), a color typical for Mn(III)-PP (Qian et al, 2019). High-valent Mn in solution, which hereafter refers to Mn(III)-PP, was quantified using Leucoberbelin Blue I (Zhu et al, 2017). The similar increases of aqueous Mn and of Mn(III)-PP indicated that Mn in solution was overwhelmingly trivalent and present as Mn(III)-PP (Fig.…”

Section: The Oxidation Of As(iii) By Birnessite With/without Chelating Agentsmentioning

confidence: 98%

Highly enhanced oxidation of arsenite at the surface of birnessite in the presence of pyrophosphate and the underlying reaction mechanisms

et al. 2020

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Manganese(IV) oxides, and more especially birnessite, rank among the most efficient metal oxides for As(III) oxidation and subsequent sorption, and thus for arsenic immobilization. Efficiency is limited however by the precipitation of low valence Mn (hydr)oxides at the birnessite surface that leads to its passivation. The present work investigates experimentally the influence of chelating agents on this oxidative process. Specifically, the influence of sodium pyrophosphate (PP), an efficient Mn(III) chelating agent, on As(III) oxidation by birnessite was investigated using batch experiments and different arsenic concentrations at circum-neutral pH. In the absence of PP, Mn(II/III) species are continuously generated during As(III) oxidation and adsorbed to the mineral surface. Field emission-scanning electron microscopy, synchrotron-based X-ray diffraction and Fourier transform infrared spectroscopy indicate that manganite is formed, passivating birnessite surface and thus hampering the oxidative process. In the presence of PP, generated Mn(II/III) species form soluble complexes, thus inhibiting surface passivation and promoting As(III) conversion to As(V) from 60% in the absence of PP to 100% with 3 mM PP (0.5 mM initial As(III)). Enhancement of As(III) oxidation by Mn oxides strongly depends on the affinity of the chelating agent for Mn(III) and from the induced stability of Mn(III) complexes. Compared to PP, the positive influence of oxalate, for example, on the oxidative process is more limited. The present study thus provides new insights into the possible optimization of arsenic removal from water using Mn oxides, and on the possible environmental control of arsenic contamination by these ubiquitous non-toxic mineral species.

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Section: The Oxidation Of As(iii) By Birnessite With/without Chelating Agentsmentioning

confidence: 98%

Highly enhanced oxidation of arsenite at the surface of birnessite in the presence of pyrophosphate and the underlying reaction mechanisms

et al. 2020

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“…Although Mn AOS of birnessite has been extensively measured using redox titration or X-ray absorption near-edge spectroscopy (XANES) [40], XPS can provide information about AOS changes specifically on the surface or in the near-surface region of birnessite after reaction with aqueous Mn 2+ at a lower concentration range. Figure 3a shows the survey scan of the as-synthesized birnessite.…”

Section: Aos Of Birnessite After Reaction With Aqueous Mn(ii)mentioning

confidence: 99%

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

Liu

Zhang

et al. 2020

Minerals

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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.

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“…For O 1s, an example of the calculation is provided in the Supporting Information section (Table S1) and calculates a value of +3.5. The bulk AOS was determined by a chemical titration method, which involves reaction of oxalic acid with the sample and then back-titration by KMnO 4 , 46 which determined AOS of +3.2. The AOS from the three methods averages to +3.4.…”

Section: Resultsmentioning

confidence: 99%

Photochemical Water Oxidation in a Buffered Tris(2,2′-bipyridyl)ruthenium–Persulfate System Using Iron(III)-Modified Potassium Manganese Oxides as Catalysts

Shrestha

Dutta

2018

ACS Omega

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Study of manganese oxides for electrocatalytic and photocatalytic oxidation of water is an active area of research. The starting material in this study is a high-surface-area disordered birnessite-like material with K + in the interlayers (KMnOx). Upon ion-exchange with Fe 3+ , the disordered layer structure collapses (Fe(IE)MnOx), and the surface area is slightly increased. Structural analysis of the Fe(IE)MnOx included examination of its morphology, crystal structure, vibrational spectra, and manganese oxidation states. Using the Ru(bpy) 3 2+ –persulfate system, the dissolved and headspace oxygen upon visible light photolysis with highly dispersed Fe(IE)MnOx was measured. The photocatalytic activity for O 2 evolution of the Fe(IE)MnOx was three times better than KMnOx, with the highest rate being 9.3 mmol O 2 mol Mn –1 s –1 . The improvement of the photocatalytic activity was proposed to arise from the increased disorder and interaction of Fe 3+ with the MnO 6 octahedra. As a benchmark, colloidal IrO 2 was a better photocatalyst by a factor of ∼75 over Fe(IE)MnOx.

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Rapid determination of the Mn average oxidation state of Mn oxides with a novel two-step colorimetric method

Abstract: The Mn average oxidation state (Mn AOS) of Mn oxides has a significant impact on their reactivity towards trace metals and organic contaminants via sorption, catalysis and oxidation processes.

Cited by 44 publications

References 33 publications

Highly enhanced oxidation of arsenite at the surface of birnessite in the presence of pyrophosphate and the underlying reaction mechanisms

Highly enhanced oxidation of arsenite at the surface of birnessite in the presence of pyrophosphate and the underlying reaction mechanisms

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

Photochemical Water Oxidation in a Buffered Tris(2,2′-bipyridyl)ruthenium–Persulfate System Using Iron(III)-Modified Potassium Manganese Oxides as Catalysts

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