Chemical Engineering Journal 168 (2011) 134–139
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Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej
Degradation of methyl orange by UV/H
2
O
2
advanced oxidation process
Shaker Haji
∗
, Baghdad Benstaali, Nader Al-Bastaki
Department of Chemical Engineering, College of Engineering, University of Bahrain, P.O. 32038, Isa Town, Bahrain
article info
Article history:
Received 12 August 2010
Received in revised form
14 December 2010
Accepted 15 December 2010
Keywords:
Methyl orange dye
UV/H2O2 process
Photochemical degradation
Initial reaction rate
Kinetics
abstract
The degradation of the methyl orange (MO) dye was investigated using advanced oxidation process (AOP)
by exposing MO aqueous solution to UV irradiation after the addition of hydrogen peroxide (H
2
O
2
). The
presence of H
2
O
2
in MO solutions accelerated the dye degradation process. For instance, a complete degra-
dation was achieved in 3 min when 0.1 mL of H
2
O
2
aqueous solution was added to 20 mL of 0.078 mM
MO solution compared to only 26% degradation achieved in 4 h in the absence of H
2
O
2
. The degradation
of MO molecules was accompanied by the decolorization of the solution. A thorough investigation of the
AOP process was carried out by studying the influence of the dye concentration, H
2
O
2
dosage, UV irradi-
ation power, and the area of the solution exposed to the UV source. It was found that, at the investigated
ranges, the initial dye degradation rate increased with the increase in the initial dye concentration, UV
irradiation power, and the surface area of the solution exposed to UV irradiation. An optimum concentra-
tion of H
2
O
2
was found to exist for the MO degradation reaction. AOP by UV/H
2
O
2
treatment was found
to be a technically feasible approach for the decolorization of MO aqueous solutions.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
An increasing interest is noticed in improving the technical
means of treatment of industrial wastes owing to their toxic and
hazardous organic compounds contents. The combination of one
treatment technique (adsorption, oxidation, reduction, electro-
chemical, and biological processes) with the addition of reaction
stimulators, such as catalysts, electromagnetic radiations, and
membranes, is found to lead to more efficient and reliable meth-
ods of treatment. In addition, advanced oxidation processes (AOPs)
became very common for the treatment of industrial wastes con-
taining organic dyes. AOP is based on the generation of highly
reactive radicals, which are very strong oxidizing agents (e.g.
•
OH,
E
0
= 2.8 V/NHE) at conditions near ambient temperature and pres-
sure. Many researchers reported on the effectiveness of AOPs with
or without its combination with other techniques.
Marto et al. reported on the photocatalytic degradation of the
organic dye Orange II in aqueous solutions combined with ZnO
active layers deposited on screen-printed ceramic tiles where a
decolorization rate over 0.015 min
-1
was achieved [1]. Al-Bastaki
et al. reported on the advantage of using membranes in treat-
ing dyed industrial wastewater [2,3]. Photo-degradation of MO by
Advanced Fenton Process using zero valent metallic iron was inves-
tigated and the efficiency of the process was examined with the
combination of hydrogen peroxide (H
2
O
2
), ammonium persulfate
∗
Corresponding author. Tel.: +973 17876104; fax: +973 17680935.
E-mail address: haji@eng.uob.bh (S. Haji).
((NH
4
)
2
S
2
O
8
), and ultraviolet (UV) irradiation [4]. Synergistic effect
was reported when ultrasound and ozone were collectively used
for the decolorization of MO solutions [5]. Razaee et al. reported on
the decolorization of reactive blue 19 in less than 30 min using a
process where a UV-C lamp (15 W) was combined with potassium
persulfate (K
2
S
2
O
8
) compared to the chemical oxidation process
which took 5 h to achieve similar results [6]. Amin et al. reported
on the influence of few experimental parameters such as UV inten-
sity, pH of the solution, and H
2
O
2
dosage on the degradation of
Blue Sulfur dye present in synthetic aqueous solutions [7]. Ale-
boyeh et al. [8] investigated the degradation of Acid Orange 8
(AO8), Acid Blue 74 (AB74), and MO through the UV/H
2
O
2
pro-
cess using a continuous photochemical reactor with a 15 W low
pressure mercury lamp and reported that the decolorization fol-
lowed an apparent first order kinetics with respect to the dye
concentration. It was also reported that hydrogen peroxide plays
an important role in the enhancement of the decolorization rate
of azo dyes. However, when its concentration exceeds a specific
value, the excess H
2
O
2
works as a hydroxyl radical self-consumer
rather than a producer and, therefore, reduces the system oxidizing
power [8,9].
In this study MO – which is a water soluble azo dye that is
widely used in textile, printing, paper, pharmaceutical, and food
industries [10] – was used as a model dye for studying the effective-
ness of UV/H
2
O
2
process on the decolorization of dyed industrial
wastewater. We emphasized, in this work, on the influence of the
concentration of MO, the H
2
O
2
dosage, the UV intensity, and the dye
solution area exposed to UV radiation on the dye degradation rate.
This study shall help in better understanding the UV/H
2
O
2
process
1385-8947/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.cej.2010.12.050