Kinetics of the methylene blue oxidation by cerium(IV) in sulphuric acid solutions

Katafias, Anna; Kita, P.; Wrzeszcz, Grzegorz; Mills, Andrew

doi:10.1007/s11243-006-0120-3

Cited by 21 publications

(19 citation statements)

References 17 publications

(17 reference statements)

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“…2 and 3. The radical nature of these species, which were also generated using cerium(IV), was confirmed by their EPR spectra in our previous studies [17,18]. The extremely high reactivity of the thionine radical makes its detection impossible.…”

Section: Kinetic Measurementssupporting

confidence: 54%

“…Although most of the manganese(II)-manganese(III) complexes belong to the Class I according to the Robin-Day classification [29], the found optical properties suggest rather a Class II case for the Mn(III)-SO 4 -Mn(II) mixed-valence complex. The changes within the visible spectrum range reported by Pinto et al [23], namely an absorbance decrease with an increase in the sulfuric acid concentration within the 1-2 M range, can be explained by the transformation of the [Mn(H 2 O) 5 [17], azure B and thionine [18] Degradation of the phenothiazine dyes by manganese(III) could be examined only at sulfuric acid concentrations higher than 2 M because, as outlined above, at lower H 2 SO 4 concentrations, the sulfato manganese(III) complexes are not stable. On the other hand, within the 2-5 M range, sulfuric acid concentration affects the reaction rate only slightly.…”

Section: Kinetic Measurementsmentioning

confidence: 89%

“…Previously, we have reported kinetic and mechanistic studies on oxidative degradation of some highly stable phenothiazine dyes of wide application, namely methylene blue (MB), azure B (AB) and thionine (TH), by another powerful one-electron oxidant, namely cerium(IV) in sulfuric acid media [17,18]. The importance of manganese(III) in electron transfer processes has inspired us to use it as a degradation agent for these dyes.…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Katafias

Fenska

2011

Transition Met Chem

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Manganese(III) sulfato complexes cause the oxidative degradation of methylene blue and its partially and fully N-demethylated derivatives, azure B and thionine dyes, respectively, in sulfuric acid media. The reaction proceeds through a colored reactive organic radical generated in the first stage via one-electron oxidation of the starting material, leading to a mixture of N-demethylated and/or deaminated species. The rates of formation of the methylene blue and azure B radicals are much higher than those of their further decomposition, whereas the generation of the thionine radical is much slower than its immeasurably fast decay. The kinetics of decomposition of all three dyes and the methylene blue and azure B radicals were studied spectrophotometrically under isolation conditions at 298 K. The first stage of each reaction proceeds according to a second-order rate expression, being first order in the dyes and in the manganese(III) concentrations. Dependence of the pseudo-firstorder rate constants on the oxidant concentration for the second stage exhibits a saturation effect under the applied conditions. It is postulated that electron transfer takes place between the [Mn(SO 4 ) 3 ] 3-complex and the protonated form of the dye. The reactivity order of the dyes as determined from the second-order rate constants for the first reaction stage corresponds to the order of their HOMO energies.

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Section: Kinetic Measurementssupporting

confidence: 54%

Section: Kinetic Measurementsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Katafias

Fenska

2011

Transition Met Chem

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“…3). MVB is also the main product of the nucleophile attack of MB + by OH - [26,27]. The addition of acetone at the end the of electrolysis dissolves the dark precipitate and returns the slight black solution blue (λ max : 610 nm).…”

Section: Visible Spectroscopy Analysismentioning

confidence: 99%

“…These include biological and physicochemical methods such as flocculation combined with flotation, adsorption, membrane filtration, coagulation, and ion exchange. The literature is rich in articles about the kinetic studies of the reduction and oxidation of MB + chemically [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Kinetic Study of the Electrochemical Oxidation of Methylene Blue with Pt Electrode

Hassan¹,

Jamal²

2012

Port. Electrochim. Acta

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Kinetic study of the indirect oxidation of methylene blue on Pt electrode in presence of several strong electrolytes is undertaken. Different operating conditions that affected the treatment process were studied in order to find the best conditions. The order with respect to methylene blue is zero order in presence of chloride, but it is second order in presence of bromide. The oxidation rate was affected by current density, halide concentration (KCl, KBr), nature of supporting electrolyte and initial pH. However, the initial dye concentration and temperature did not show a significant effect. The oxidation of methylene blue in presence of iodide, fluoride and sulfate is absent, but it is important in presence of chloride and bromide. The product of the indirect oxidation is the chloronated (bromonated) methylene violet bernthsen.

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Molecular Revealing the High‐stable Polycyclic Azine Derivatives for Long‐Lifetime Aqueous Organic Flow Batteries

Zhang,

Li,

Liu

et al. 2023

Adv Funct Materials

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Soluble organic molecules with diverse and highly tunable structures are receiving more and more attention as redox‐active materials for aqueous organic flow batteries (AOFBs). However, the undesirable parasitic reactions of redox‐active molecules restrict their practical application. Herein, a general molecular stabilization strategy is proposed by introducing amino groups on 3,7‐positions of polycyclic azine derivatives (phenothiazine and phenoxazine compounds) to effectively enhance the redox activity and electrochemical stability of molecules. The theoretical calculation and a series of electrochemical analyses revealed that the 3,7‐substituted amino groups serving as the redox active sites can stabilize the intermediate radicals by delocalizing the electron density in the acidic solution, preventing nucleophilic/electrophilic attack. As a result, the designed 3,7‐bis‐((2‐hydroxyethyl)(methyl)amino)phenothiazin‐5‐ium bromide not only achieved the remarkable electrochemical cycling performance in the flow cell with an ultra‐low‐capacity fade rate of 0.00029% per cycle for 18000 cycles (62 days) and but also delivered a stable high capacity of 47 Ah L−1 (with capacity fade 0.0056% per cycle, 0.077% per day) under ambient condition. Such finding undoubtedly provides a guidance to design stable redox‐active molecules for AOFBs.

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Kinetics of the methylene blue oxidation by cerium(IV) in sulphuric acid solutions

Cited by 21 publications

References 17 publications

Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Kinetic Study of the Electrochemical Oxidation of Methylene Blue with Pt Electrode

Molecular Revealing the High‐stable Polycyclic Azine Derivatives for Long‐Lifetime Aqueous Organic Flow Batteries

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