Photocatalytic Degradation of Aqueous C.I. Reactive Violet 5 Using Bulk Zinc Oxide (ZnO) Slurry
Jeannie Lynn J. Cabansag1*, Jesus C. Dumelod2, John Cyrus O. Alfaro2, John D. Arsenal2, Jolivette C. Sambot2, Lorna T. Enerva2, and Julius L. Leaño Jr.1
1Research and Development Division, Philippine Textile Research Institute,
Department of Science and Technology, Bicutan, Taguig City
2Department of Natural Sciences, College of Science, Polytechnic University of the Philippines
The degradation of aqueous C.I. Reactive violet 5 dye under UV light with bulk zinc oxide (ZnO) slurry as the photocatalyst was studied. The effects of varying amounts of zinc oxide, dye concentration, exposure time, pH, temperature and lamp intensity on degradation were evaluated. UV irradation was found to enhance dye degradation by about 90% immediately after 30 minutes of exposure time, for low dye concentration of 2 x 10-5 M. The rate of dye degradation increased as the amount of zinc oxide increased until optimum loading was achieved. At 3,840 ppm ZnO concentration, 5 x 10-5 M (40 ppm) dye is degraded by 74% after 30 min of irradiation and was nearly 100% degraded after 90 min at pH 7 and temperature of 30°C. The degradation rate follows a first order kinetics with respect to dye concentration, with the rate constant decreasing as dye concentration increases at constant amount of zinc oxide. The rate of RV5 degradation is determined at 9.3 x 10-5 M/h using 3840 ppm ZnO under neutral pH, temperature of 30°C and 20W lamp intensity. Increased pH, temperature and lamp intensity further accelerate dye degradation by about 38.0%, 53.3%, and 43.2%, respectively. The use of zinc oxide provides a simple and efficient method for photocatalytic degradation of azo dyes in wastewater.
Dye pollutants from the textile industry contribute to considerable environmental contaminants. In dyeing process, about 1-15% of dye is discharged, accounting to a large volume of effluents which could lead to aesthetic pollution, eutrophication, and perturbations in marine and aquatic ecosystem . . . . . . . . . . . .
CHEN CC. 2007. Degradation pathways of ethyl violet by photocatalytic reaction with ZnO dispersions. J Mol Catal A 264: 82-92.
CHUNG YC, CHEN CY. 2009. Degradation of azo dye reactive violet 5 by TiO2 photocatalysis. Environ Chem Lett 7:347-352.
COMPARELLI R, FANIZZA E, CURRI ML, COZZOLI PD, MASCOLO G, AGOSTANO A. 2005. UVinduced photocatalytic degradation of azo dyes by organic-capped anatase ZnO nanocrystals immobilized onto Substrates. Appl Cat B 60:1-11.
DANESHVAR N, SALARIB D, KHATAEEA AR. 2004. Photocatalytic degradation of azo dye acid red 14 in water on ZnO as an alternative catalyst to TiO2 . J Photochem Photobiol A 162: 317-322.
MOZIA S, TOMASZEWSKA M, MORAWSKI AW. 2005. Photocatalytic degradation of azo dye Acid Red 18. Desalination 185: 449-456.
NAGESWARA RAO A, SIVASANKAR B, SADASIVAM V. 2009. Kinetic Studies on the photocatalytic degradation of Direct yellow 12 in the presence of ZnO catalyst. J Mol Catal A 306: 77-81.
SAUER T, CESCONETO NETO G, JOSE HJ, MOREIRA RFPM. 2002. Kinetics of photocatalytic degradation of reactive dyes in a TiO2 slurry reactor. J Photochem Photobiol A 149: 147-154.
SONG YL, LI JT, BAI B. 2010. TiO2-assisted Photodegradation of Direct Blue 78 in Aqueous Solution in Sunlight. Water Air Soil Pollut 213: 311-317.
YASSITEPE E, YATMAZ HC, OZTURK C, OZTURK K, DURAN C. 2008. Photocatalytic efficiency of ZnO plates in degradation of azo dye solutions. J Photochem Photobiol B 198: 1-6.