The mechanism and kinetics of the electrochemical cleavage of azo bond of 2-hydroxy-5-sulfophenyl-azo-benzoic acids

Mandić, Zoran; Nigović, Biljana; Šimunić, Branimir

doi:10.1016/j.electacta.2003.09.015

Cited by 39 publications

(16 citation statements)

References 19 publications

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“…The reduction is facilitated by electron withdrawing groups and follows the expected substituent effect: SO 3 À > H > OH. The reduction potentials of all the investigated compounds were in good agreement with previous findings at glassy carbon electrode [5,6,9].…”

Section: Mechanisms Of the Electrode Reactionssupporting

confidence: 89%

“…The electrochemical behavior of differently substituted azosalicylic acids has been studied by cyclic voltammetry [5 -7], coulometry [6,8] and chronoamperometry [9] at glassy carbon electrodes. The reduction of these compounds yield either the corresponding amines, as a result of the cleavage of azo bonds, or a hydrazo intermediate, depending on the pH of the medium and the substitution on aromatic rings.…”

Section: Introductionmentioning

confidence: 99%

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Electroanalytical Studies of Biologically Active Azosalicylic Acid at a Hanging Mercury Drop Electrode

2005

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The electrochemical behavior of disodium 3,3'-azobis-(6-hydroxy-)benzoate (olsalazine sodium), 2-hydroxy-5-[(4-sulfophenyl)azo]benzoic acid and 2-hydroxy-5-azo-benzoic acid was studied as a simple model of the metabolic reduction of azosalicylic acids using cyclic and square-wave voltammetry. The stability of the hydrazo intermediate generated in the electroreduction process is strongly dependent on pH and the effect of different substituents in the aromatic ring adjacent to the azo bridge. The electrode mechanism of azosalicylic acids at hanging mercury drop electrode exhibits characteristic properties of a surface redox reaction. The kinetic parameters of azo/hydrazo reduction, such as the standard redox reaction rate constant and the electron transfer coefficient were estimated applying the methods of a split SW peak and a quasireversible maximum. A sensitive analytical method for the determination of trace level of biologically active azosalicylic acids by square-wave voltammetry based on adsorptive stripping technique is described.

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Section: Mechanisms Of the Electrode Reactionssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Electroanalytical Studies of Biologically Active Azosalicylic Acid at a Hanging Mercury Drop Electrode

2005

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“…They can be hardly biodegraded under an aerobic environment, but can be decolourized by anaerobic biological process (Knapp & Newby 1995;Supaka et al 2004). It is well known that the bacterial cleavage of azo compounds is a reductive process (Mandic´et al 2003). Colour removal depends on the reduction potential of the electron donors and acceptors, because the ratecontrolling step involves reduction equilibrium between the dye and the extracellular reducing agent.…”

Section: Introductionmentioning

confidence: 99%

Correlation of anaerobic biodegradability and the electrochemical characteristic of azo dyes

Guo¹,

Wang²,

Xiang³

et al. 2005

Biodegradation

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Some experiments were conducted to study some electrochemical factors affecting the bacterial reduction (cleavage) of azo dyes, knowledge of which will be useful in the wastewater treatments of azo dyes. A common mixed culture was used as a test organism and the reductions of Acid Yellow 4, 11, 17 and Acid Yellow BIS were studied. It was found that the azo dyes were reduced at different rates, which could be correlated with the reduction potential of the azo compounds in cyclic voltammetric experiments. Acid Yellow BIS (E (r)--616.75 mV) was reduced at the highest rate of 0.0284 mol g dry cell weight(-1) h(-1), Acid Yellow 11 (E (r)--593.25 mV) at 0.0245 mol g dry cell weight(-1) h(-1) and Acid Yellow 4 (E (r)--513 mV) at 0.0178 mol g dry cell weight(-1) h(-1). At the same time, the decolorization rate of Acid Yellow 17 (E (r)--627.5 mV) was 0.0238 mol g dry cell weight(-1) h(-1), which was affected by the nature of chlorine substituent. Reduction of these azo dyes did not occur under aeration conditions. These studies with a common mixed culture indicate that the reduction of azo dyes may be influenced by the chemical nature of the azo compound. The reduction potential is a preliminary tool to predict the decolorization capacity of oxidative and reductive biocatalysts.

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“…Once the azo bond is cleaved, the conjugated structure of azo dye is destructed, accompanied by the complete color removal in the visible region rather than TOC removal [27,28]. Sulfanilamide and 1-amino-2-naphtol are the most probable products resulted from electrons or active hydrogen atoms reduction, among which 1-amino-2-naphtol is the most possible chemical susceptible to oxidative species.…”

Section: Reaction Pathways Of Electrochemically Assisted Photocatalytmentioning

confidence: 99%

Electrochemically assisted photocatalytic degradation of Orange II: Influence of initial pH values

Zhang

et al. 2006

Journal of Molecular Catalysis A: Chemical

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The effect of initial pH values in solution was studied in the process of electrochemically assisted photocatalytic degradation (EAPD) of an azo-dye Orange II using a ␤-PbO 2 electrode modified by TiO 2 . The removal of color and total organic carbon (TOC) from the simulated dye wastewater was experimentally investigated at pH 2.29 and 11.52. The degradation products were examined by means of HPLC, UV-vis and FTIR spectra analyses. Similar color removal rate was achieved at pH 2.29 and 11.52, but the removal of TOC at pH 2.29 was 20.0% higher than that at pH 11.52. The dye was oxidized the most completely at pH 2.29 than at 11.52 and 6.88. There was a new absorbance peak at ca. 255 nm generated at ca. 40 min only at pH 11.52, which was ascribed to the quinonic compounds resulted from 1-amino-2-naphtol. A reductive degradation pathway by reductive species such as active electrons was proposed, which only led to the removal of color in parallel with the oxidative degradation pathway. Hole process was proved to be the dominating process at pH 2.29 and the effect of the reductive species was also significant at pH 11.52. Initial pH values were proved to have only influenced the degradation pathways to some extent, and therefore resulted in the disparity of the removal of color and TOC. High mineralization rate was still achieved in spite of the initial pH values in solution due to the prevailing photocatalytic oxidation mechanism.

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The mechanism and kinetics of the electrochemical cleavage of azo bond of 2-hydroxy-5-sulfophenyl-azo-benzoic acids

Cited by 39 publications

References 19 publications

Electroanalytical Studies of Biologically Active Azosalicylic Acid at a Hanging Mercury Drop Electrode

Electroanalytical Studies of Biologically Active Azosalicylic Acid at a Hanging Mercury Drop Electrode

Correlation of anaerobic biodegradability and the electrochemical characteristic of azo dyes

Electrochemically assisted photocatalytic degradation of Orange II: Influence of initial pH values

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