Elsevier

Dyes and Pigments

Volume 59, Issue 2, November 2003, Pages 173-179
Dyes and Pigments

Reactive dye decolorization using combined ultrasound/H2O2

https://doi.org/10.1016/S0143-7208(03)00101-3Get rights and content

Abstract

The decolorization of six vinylsulphone reactive dyes (C.I. Reactive Yellow 15, C.I. Reactive Red 22, C.I. Reactive Blue 28, Remazol Dark Black N 150%, C.I. Reactive Blue 220 and C.I. Reactive Black 5) in aqueous solution was investigated using ultrasound and ultrasound/ hydrogen peroxide degradation. Two different concentration levels of hydrogen peroxide were used. The efficiency of the decolorization was evaluated by measuring the absorbance of the dye solutions. The results show that ultrasound treatment was significantly enhanced in the presence of H2O2.

Introduction

It is known that reactive dyes form a covalent bond with the –OH groups of cellulosic fibres and the amino groups of wool and amino groups of PA fibres, which is the reason for their good stability during washing. Such properties make reactive dyes popular; however reactive dyes can also react with the –OH groups of water resulting in hydrolysis of the dye. The inability of molecule dye to react with fibres contributes to pollution of the wastewater, as this aesthetic problem becomes global if we take into consideration the fact that dyeing may cause pollution with heavy metals, which are structural elements in some dyes. Decolorization of wastewater, polluted with reactive dyes is closely related to cleavage of the – C=C- and -N=N- bonds or heterocyclic and aromatic rings. The result is that the absorption of light shifts from the visible to the UV or IR region of the electromagnetic spectrum. At present three types of wastewater treatment are known, namely physical, chemical and biological.

Physical methods of treatment include precipitation, adsorption, reverse osmosis and filtration, combustion and incineration and other methods such as distillation and extraction. Chemical methods include oxidation, reduction, complexometric methods and ion exchange methods while biological methods involve aerobic and anaerobic treatments.

Environmental sonochemistry [1] is a rapidly growing area and is an example of an advanced oxidation process (AOP) that deals with the destruction of organic species in aqueous solution. Benzene, for example, well known for its resistance to the action of strong oxidants, succumbs to oxidation under ultrasonication in aqueous media. Concerning the sonochemical degradation of dyes, some attempts have been made which promoted sonolysis as a feasible method to achieve both decolorization and degradation of the dye. The C.I. Acid Black 1 dye was investigated using a combination of sonolysis and photocatalysis; it was found that sonolysis was effective for inducing faster degradation of the dye, while photocatalysis was effective for promoting degradation [2].

In the present paper we describe a comparative study of the decolorization techniques of six reactive, vinylsulphone dyes using ultrasound and ultrasound/H2O2.

Section snippets

Decolorization using H2O2

One of the more popular AOP methods for wastewater decolorization is oxidation with H2O2 which, due to its stability in pure form, needs to be activated. Hydrogen peroxide activated with UV light decomposes into OH· radicals [3], [4], [5], [6], [7], [8].

Oxidation potential of OH· radicals is much higher then that of hydrogen peroxide. Also, UV irradiation and other activators can be used for H2O2, such as Fe (II) salts (Fenton's reagent) and ozone [9]. Recently, ultrasound was described as a

Chemicals

The three dyes, namely C.I. Reactive Yellow 15, C.I. Reactive Red 22, C.I. Reactive Blue 28 were all purchased from the producer Bezema. The other three dyes, namely Remazol Dark Black N 150% (no color index), C.I. Reactive Blue 220 and C.I. Reactive Black 5 were commercial products purchased from the producer DyStar. All six dyes were used without purification. Hydrogen peroxide solution (35% w/w, with ρ=1.13 g/ml) of analytical grade was obtained from Belinka. Aqueous solutions were prepared

Results and discussion

Our results confirm the suitability of the ultrasound and ultrasound/H2O2 process as a reactive dye decolorization. The greatest percentage of decreasing of the dye concentration was established with the C.I. Reactive Black 5 dye solution. It has decreased from 10.0 mg/l to 0.38 mg/l (96.2%) after treating with ultrasound for 7 h. The concentration has been calculated from the corresponding calibration curve by measuring the absorbance at wavelength 598 nm. The concentration of the Remazol Dark

Conclusions

The decolorization of six dye solutions under ultrasound and ultrasound/H2O2 conditions was examined. The study has shown that the efficiency of the ultrasound treatment was significantly enhanced if ultrasound and H2O2 were used. The rate of color degradation was twice as fast as that accomplished by sonolysis alone. The results have shown that with a dose of 3.49 mol/l H2O2 and ultrasound treatment for 4 h the decolorization was higher than for ultrasound treatment with a dose of 0.23 mol/l H2

References (25)

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