The document investigates the decolorization of two reactive dyes (Reactive Orange 16 and Reactive Black 5) from textile wastewater using advanced oxidation methods. In single methods, ozonation at 5 g/h achieved 98% decolorization of both dyes, while ultrasound was less effective achieving only 3-14% decolorization. Combined methods applied consecutively resulted in 87-99% decolorization, while the simultaneous application of ozonation and ultrasound achieved 99-100% decolorization, indicating it is the most suitable method.

1. .
E-mail: dygserdar@gmail.com, merve_kytnci@hotmail.com, guvenc@eng.ankara.edu.tr
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Acknowledgements
This research was financially supported by the Ankara University Scientific Research Project Coordination Unit (Project No: 11B4343003).
Decolorization of Reactive Dyes from Textile
Wastewater by Advanced Oxidation Methods
Duygu Serdar*, Merve Kaytancı and Afife Güvenç
Department of Chemical Engineering, Ankara University, 06100 Ankara, TURKEY
Figure 6: Decolorization of RO 16 and RB 5 combined methods applied consecutively or simultaneously.
It was shown that the ozonation method alone yielded a decolorization of 13% and 98% for RO
16 at flow rates of 0.4 g/h and 5 g/h, respectively. The same analysis for RB 5 resulted in 91% and
100%. According to the these results, it can be seen that decolorization yield increses by
increasing the ozone flow rate. These results also indicated that ozone treatment alone is fairly
effective for both of the dyes.
The effect of frequency in the ultrasonication method used alone was investigated on the
decolorization of each dye. Accordingly, treatments at 20 kHz and 30 kHz resulted in 4% and 3%
decolorization for RO 16; 14% and 5% decolorization for RB 5, respectively. This result shows that
ultrasound is not a suitable method to remove color from textile waste waters when it is used
alone.
It was found that there is negligible difference between decolorization percentages for pH levels
of 6 and 7; both result in 98% decolorization for RO 16 at 5 g/h ozone flow rate.
In the combined methods which consecutive application was investigated, it was achieved
decolorization yields of 87% and 99% for RO 16 and RB 5, respectively.
The other combined method, the simultaneous application of the ultrasonication and the
ozonation, was resulted the highest decolorization yield of 99% and 100% for RO16 and RB 5,
respectively. This shows simultaneous combined method is more suitable than consecutive
combined method in decolorization of dyes from textile waste water.
Figure 4: Decolorization of RB 5
(C0= 50 mg/l, pH= 2, time: 50 min)
Figure 5: Decolorization of RO 16
(C0= 50 mg/l, pH= 6, time: 50 min).
Figure 1: Chemical structure for (a) RO 16 and (b) RB 5.
Reactive Orange 16 and Reactive Black 5 were used in this study.
Waste waters from the textile industries are one of the most difficult ones to treat because
they contain various chemicals and especially dyestuffs. Dyes usually have a synthetic origin
and complex aromatic molecular structures, which make them more stable and more difficult
to be biodegraded. It was reported that approximately 90% of reactive dyes, which are
extensively used in the worldwide textile industry, entering activated sludge process pass
through with no change; some parts can be degraded under anaerobic biological treatment
but reduction products are toxic. Although the methods used for the removal of dyestuffs like
ozonation, chemical reduction-oxidation, coagulation-flocculation, adsorption, are effective,
most of them have some drawbacks such as high cost, formation of hazardous by-products,
and intensive energy requirement. The use of advanced oxidation processes for waste water
treatment has been shown to be technically feasible by numerous reports in the literature
over the years [1-5].
In this study, the decolorization of Reactive Orange 16 (RO 16) and Reactive Black 5 (RB 5),
in order to reference to the coloring agents contained in the waste water of the textile
industry, was investigated by using ultrasound (US) at 20 kHz and 30 kHz and ozonation
(OZ) at 0.4 and 5 g/h both alone and combined systems. For determining the pH effect, pH
values of 2, 6,7, and 10 were studied and optimum pH was found as 6 for RO 16 and as 2 for
RB 5. Among the single methods, it was found that the most effective method was the
ozonation ( 5g/h) providing 98% decolorization for both dyes in 50 minutes.
Furthermore, in the combined methods which consecutive application was investigated, it
was achieved decolorization yields of 87% and 99% for RO 16 and RB 5, respectively ( 50
mg/ l, 5 g/ h, 20 kHz, 50 min).
Finally, the combined method, which is the simultaneous application of the ultrasonication
and the ozonation, was applied and resulted in decolorization of 99% and 100% for RO16
and RB 5, respectively (50 mg/l, 5 g/h, 20 kHz, 50 min).
Keywords: Reactive Orange 16, Reactive Black 5, decolorization, ozone, ultrasound
Summary
In single methods, the above mentioned dyes are
prepared with a initial concentration of 50 mg/l (C0)
in all of the experiments.The room temperature is
the starting point for heat and the temperature is
not specifically controlled afterwards. For US
method, UP100H Heilscher Ultrasonic
Homogenizer (30 kHz, 100 W) and Ultrasonic
Homogenizer Sonopuls HD 3400 (20kHz); in OZ
experiments, Opal ozone generator (0.4 g/ h ozone
flow rate) and Waterfun ozone generator (5 g/saat)
were used to determine the ultrasonic effect and
the ozone dosage effect in decolorization.
Methods
Conclusions
Results
The results of single method decolorization experiments that are conducted by using the ultrasonic homogenizer
(20 kHz and 30 kHz) and the ozone generator (0.4 g/h and 5 g/h) are shown in Fig. 2, 4 and 6 and Fig. 3, 5 and 6
for RB 5 and RO16, respectively.
λmax= 496 nm
λmax= 595 nm
Firstly, standard solutions of each dye were
prepared to draw calibration lines in their
maximum wave lengths by using Shimadzu
Spectrofotometer (UV-1601).
Maximum wavelengths of dyes were found as
496 nm and 595 nm for RO 16 and RB 5,
respectively.
In the combined methods which consecutive
application was investigated, the treatment
started with the ultrasonic homogenizer,
continued with the ozone generator or started
with the ozone generator and ended with the
ultrasonic homogenizer. Then, simultaneous
application of OZ and US was investigated.
For the decolorization of RO 16 and RB 5, advanced oxidation methods consisting of only OZ (0.4
g/h or 5 g/h ozone flow rate), only US (20 kHz and 30 kHz frequency) and combined methods
applied consecutively (US+OZ) or simultaneously were investigated .
Shimadzu UV 1601
Spectrofotometer
UP100H Heilscher
Ultrasonic
Homogenizer
OPAL Ozone
Generator
Waterfun Ozone
Generator
US (20 kHz) US (30 kHz) OZ (0.4g/h) OZ (5g/h) US (20 kHz) US (30 kHz) OZ (0.4 g/h) OZ (5g/h)
OZ(5g/h)+ US(20kHz) consecutive
method for RO 16
OZ(5g/h)+ US(20kHz)
consecutive method for RB 5
OZ(5g/h)+ US(20kHz)
simultaneous method for RO 16
OZ(5g/h)+ US(20kHz)
simultaneous method for RB 5
HD 3400 Sonopuls
Ultrasonic
Homogenizer
Figure 2: Decolorization of RB 5 by single US or OZ methods
(C0= 50 mg/l, pH= 2)
Figure 3: Decolorization of RO 16 by single US or OZ methods
(C0= 50 mg/l, pH= 6)
2nd INTERNATIONAL CONFERENCE ON
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Materials