DEGRADATION OF TEXTILE DYES BY APPLICATION OF ULTRASOUND
Special Symposium - Environmental Protection & Sustainability
Environmental Protection & Sustainability - I
Keywords: Ultrasound, Degradation, Reactive Red 2, Basic Yellow 2, Reactive Blue 4
Abstract
Enormous amounts of textile wastewater which is heavily charged with unconsumed dyes and other assistant chemicals are being produced in the textile industry processes [1]. Dyes which include nearly 10.000 different types are produced over 7*105 tons annually on average. Ten percent of these dyes have been discharged to environment by effluent of industrial wastewater treatment systems [2]. It is not desired to discharge the effluents formed by this way, because these effluents destroy nature and threaten human health. Azo dyes which are textile dyes themselves are not toxic. Also, they do not degrade in aerobic conditions due to their structural recalcitrance. But, under anaerobic conditions (e.g. in river sediments) azo dyes are cleaved by microorganisms to form potentially carcinogenic aromatic amines [3]. It is well known that advanced oxidation processes are used to remove hazardous organic compounds and dyes from water and effluents of wastewater treatment plants [4, 5]. Among the advanced oxidation techniques, it can be said that sonolysis is one of rapidly developed techniques. Ultrasound which diffuse into several medium are vertical waves. When ultrasound passes through a liquid, it induces vibrational motions of the intermolecular bonds, and energy is thus transferred through the medium in the propagational direction [1]. When it is used in fluids such as water, organic solvents and liquid helium [5], gas-filled microbubbles first form in the medium and then growth and suddenly implode. This phenomenon is called as cavitation. Spot temperature and pressure (1000 atm and 5000 K) [5], in the bubbles are observed during cavitation. Localized high temperatures and pressures result in formation of highly concentrated oxidizing species such as hydroxyl radicals (HO•), hydrogen radicals (H•), hyroperoxyl radicals (HO2) and H2O2 [2]. Thus ultrasonic irradiation shows promise and has the potential for use in environmental remediation.
The aim of this study is the degradation of azo dyes by ultrasound. The sonicdegradation of three dyes, reactive red 2 (RR2), reactive blue 4 (RB4) and basic yellow 2 (BY2) were studied for 5, 10, 25, 50 and 100 mg/L initial concentration by the application of pulse (5 s-on, 5 s-off or 0.1 s-on, 9.9 s-off) and continuously ultrasonic irradiation at 20 kHz. The degradation was carried out in a cylindrical glass reactor with jacket (100 ml) during 6 hours. The dye concentrations before and after ultrasonic irradiation were analyzed by UV-VIS spectrophotometer at 538.5, 596 and 430 nm for RR2, RB4 and BY2, respectively.
It was found that degradation efficiency increased with decreasing the initial concentration. The degradation efficiencies for RR2, RB4 and BY2 were 33 %, 28 % and 11 % for 100 mg/L initial concentration and 80 %, 70 % and 60 % for 10 mg/L initial concentration, respectively, by continuously irradiation at 5 hours. It was observed that the degradation efficiency increased with increasing the reaction time by the application of pulse and continuously ultrasonic irradiation. The degradation efficiencies for RR2 and BY2 were 28 % and 7 % at 1 hour and 72 % and 42 % at 6 hours by continuously irradiation for 25 mg/L initial concentration. It could not was obtained an efficient degradation when pulse irradiation (0.1 s-on, 9.9 s-off) was applied in the system. At this condition, it was found that the degradation efficiencies for RR2, BY2 and RB4 were 0.5 %, 1 % and 6 % for 25 mg/L initial concentration. The maximum degradation efficiency for each three dyes was observed when the ultrasonic irradiation was continuously applied to the system.
References
1. Vajnhandl, S., Marechal, A., M., Dyes and Pigments, vol: 65, 89-101, 2005.
2. Sponza ,D., Işık, M. Atalay, H., DEU, Science and Eng. Review, 2(3):23-24, 2000.
3. Rehorek, A., Tauber, M., Gübitz, G., Ultrasonics Sonochemistry, vol: 11, 177-182, 2004.
4. a) Gogate, P., R., Pandit, A., B., Advances in Environmental Research I, 8, 501-551, 2004
b) Gogate, P., R., Pandit, A., B., Advances in Environmental Research II, 8, 553-597, 2004
5. Suslick K.S., Ultrasound, VCH Publishers, 1, 129-130, 144, 1988.
Presented Monday 17, 11:35 to 11:55, in session Environmental Protection & Sustainability - I (S-7A).
