Degradation of Sulfonated Azo Dyes with Sodium Percarbonate

Ohura, Ritsuko; Katayama, Akira; Takagishi, Tohru

doi:10.1177/004051759206200909

Cited by 12 publications

(3 citation statements)

References 6 publications

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“…These dyes predominantly exist in neutral aqueous solutions in the hydrazone tautomeric form,30a which is responsible for the dark colors. Although the hydrazone tautomer is the reactive form toward the perhydroxyl anion, 30a, the dye common anion is the reactive species during the oxidation by peracids and hypochlorites. Because the p K A values of the ground-state dyes are >10, at pH 7.0 the dyes are most likely to react with the • OH in their hydrazone form.…”

Section: Introductionmentioning

confidence: 99%

Free-Radical-Induced Oxidation and Reduction of 1-Arylazo-2-naphthol Dyes: A Radiation Chemical Study

et al. 2002

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The kinetics and transient optical absorption spectra of the intermediates formed in the reaction of •OH, N3 •, and e- aq with 1-arylazo-2-naphthol and its ortho- and para-substituted chloro, methyl and methoxy derivatives at pH 7.0 have been studied by pulse radiolysis. The rate constants for the reaction of •OH and the nucleophilic hydrated electron (e- aq) with these compounds are (1.0−1.2) × 1010 M-1 s-1 and (0.8−2.5) × 1010 M-1 s-1. The reaction of N3 • with these azo dyes is more selective (ρ+ = −2.0) with the rate constants varying between 0.1 × 109 and 8 × 109 M-1 s-1 depending upon the substituent. The transient optical absorption spectra of the intermediates formed in the reaction of the dyes with •OH are different from the corresponding spectra of the intermediates observed in the reaction of the dyes with N3 •. The •OH radical reacts with the dyes by addition to form the •OH adducts, whereas N3 • reacts with the dyes by direct one-electron transfer to form the one-electron oxidized dye radical. The pK A of the dye radical of the para-methoxy derivative was determined to be 5.2. This radical decays bimolecularly, predominantly by disproportionation, whereas the •OH adducts of the dyes also decay bimolecularly but predominantly by dimerization. The initially formed radical anion in the reaction of e- aq with the unsubstituted dye protonates rapidly to give the hydrazyl radical, which decays bimolecularly by disproportionation. Of the radicals studied, the •OH-induced oxidation of the dyes is the most effective process leading to decolorization of the dyes at pH 7.0.

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Section: Introductionmentioning

confidence: 99%

Free-Radical-Induced Oxidation and Reduction of 1-Arylazo-2-naphthol Dyes: A Radiation Chemical Study

et al. 2002

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“…The oxidation of azo dyes has attracted much attention in recent years. [1][2][3][4][5][6][7][8][9][10][11] This has been stimulated by environmental, commercial and social pressures, particularly environmental concerns over residual dyes present in waste water streams, 9-11 dye fading due to hypochlorite 2-4 used as a disinfectant in water supplies or the presence of low temperature bleaches in detergents. 8 Although previous studies represent significant steps forward in generating empirical rules governing oxidation, further progress is required in developing the underlying science base.…”

Section: Introductionmentioning

confidence: 99%

Kinetic investigations of azo dye oxidation in aqueous media

Oakes¹,

Gratton²

1998

J. Chem. Soc., Perkin Trans. 2

105

104

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“…The initial decoloration rate of dye is obtained from the slope of the tangent to the curve, which represents the relationship between dye concentration and electrolysis time, i.e., And though the dyes are different, the decoloration reactions of methylene blue observed in this experiment, as shown in Figure 1, and azo dyes such as Orange I-IV reported in our earlier paper [3] seem to be very slow compared with the effective peroxide bleaching of azo dyes by hydrogen peroxide and sodium percarbonate reported by Thompson et ai. [ 18] and Ohura et al [13), respectively. For these reactions, the half-life [4] was approximately 30-40 seconds, whereas in our case it was clearly much longer than 30 minutes, the longest 342 time used in our measurements.…”

Section: Bleaching Of Dyes In the Presence Of Electrogenerated Oxo-spmentioning

confidence: 96%

Bleaching of Cotton Fabric by Electrogenerated Species—Decoloration of Coloring Matter by Electrolysis

Fukatsu

Kokot

2000

Textile Research Journal

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Decoloration of dyes such as methylene blue and tartrazine solutions is investigated by subjecting dye solution to electrogenerated oxygen or chlorine species in electrolytes at a Pt anode. Decoloration is weak in the presence of electrogenerated oxygen species but increases in the KCl electrolyte. Decoloration in this solution is accomplished by the electrogenerated hypochlorite ion. Also, when placed in contact with a Pt anode, cotton fabric dyed with reactive dyes is decolorized significantly after short-term electrolysis in an electrolyte containing KCl, but decoloration of dyed fabrics is very weak in an electrolyte that is free from KCl. . Oxidative bleaching is a process whereby coloring matter is rendered colorless by oxidation reactions. For cotton fabrics, however, catalytic damage can occur during bleaching with hydrogen peroxide [ 11 ], producing , low quality material. A model for catalytic damage has been proposed, involving exposure of the fabric to electrogenerated oxygen species at Pt [7,9], Cu, and Fe (mild steel) [10,15] electrodes. Qualitative and quantitative interpretations of oxidatively damaged fabric have also been investigated in detail by diffuse reflectance infrared spectroscopy and chemometrics [6]. It is assumed that large amounts of highly reactive oxygen species are produced during electrolysis.Various oxidizing agents such as hydrogen peroxide, sodium percarbonate, sodium hypochlorite, and sodium chlorite are widely used for bleaching cotton [14]. Different active species generated from these oxidizing agents have been proposed to play important roles in decoloring matter. Many workers reported that the bleaching mechanism is based on the formation of active species, such as free radicals [2,17] and/or activated ions [4,5,18] such as Cl', depending on the reagent used. Interaction of these active species with coloring matter results in decoloration. We have investigated the use of electrochemical methods for decolorizing azo dyes in an electrolyte solution containing halide ions [3], and we showed that the degree of decoloration was affected by the molecular structure of azo dyes. However, little is known about the process of electrochemical bleaching.In this paper, we describe some studies of the decoloration of dyes such as methylene blue (CI Basic Blue 9) and tartrazine (CI Acid Yellow 23) by electrolysis in electrolyte solutions at different temperatures and pH. In addition, since the bleaching process is generally a heterogeneous reaction, we also discuss the electrolytic bleaching of cotton fabrics dyed with CI Reactive Black 5 and Reactive Red 2. ExperimentalAnalytical grade methylene blue (CI Basic Blue 9) and tartrazine (CI Acid Yellow 23) dyes were recrystallized from aqueous ethanol. Other chemicals such as KCI, Na2S04, NaOH, and so on were also AR grade from various commercial suppliers, and were used without further purification. Purified water prepared by an Elga Elgastat Maxima UF was used for all solutions. Cotton poplin samples were chosen from a selection of labo...

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Degradation of Sulfonated Azo Dyes with Sodium Percarbonate

Cited by 12 publications

References 6 publications

Free-Radical-Induced Oxidation and Reduction of 1-Arylazo-2-naphthol Dyes: A Radiation Chemical Study

Free-Radical-Induced Oxidation and Reduction of 1-Arylazo-2-naphthol Dyes: A Radiation Chemical Study

Kinetic investigations of azo dye oxidation in aqueous media

Bleaching of Cotton Fabric by Electrogenerated Species—Decoloration of Coloring Matter by Electrolysis

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