Degradation of Carbaryl by Photolytic Ozonation
The degradation of Carbaryl, a frequently used carbamate derivative pesticide, was carried out in batch reactors by photolytic ozonation. The influencing factors such as pH, pollutant concentration and ozone dosage were studied to optimize the reaction conditions. The maximum COD removal of 78.5% was achieved in three hours at alkaline pH 9. Increase in ozone dosage from 0.12 g/h to 0.48 g/h increased degradation rate. The apparent pseudo first order rate constant for photolytic ozonation and ozonation processes were found to be 0.0209 min–1 and 0.0139 min–1 respectively which indicated the presence of highly reactive hydroxyl radicals in photolytic ozonation. Complete mineralization needs longer ozonation time and only 48% TOC removal was achieved in three-hour duration. BOD5/COD ratio increased from 0.02 to 0.38 which facilitates coupling with secondary biological treatment.
Alvares, A.B.C., Diaper, C. and S. Parsons (2001). Partial Oxidation by ozone to remove recalcitrance from wastewaters – A review. Environ. Technol., 22: 409-427.
Benitez, F.J., Heredia, J.B. and T. Gonzalez (1991). Kinetics of the reaction between Ozone and MCPA. Wat. Res., 25: 1345-1349.
Hoigne, J. (1998). Chemistry of aqueous ozone and transformation of pollutants by ozonation and advanced oxidation processes. In: The Handbook of Environmental Chemistry, Part C, Springer, Berlin.
Kasprzyk-Hordern, B., Ziolek, M. and J. Nawrocki (2003). Catalytic ozonation and methods of enhancing molecularozone reactions in water treatment. Appl. Catal. B: Environ., 46: 639-669.
Oyama, S.T. (2000). Chemical and Catalytic properties of Ozone. Catal. Rev. Sci. Eng., 42: 279-322.
Peyton, G.R., Huang, F.Y., Burleson, J.L. and W.H. Glaze (1982). Destruction of pollutants in water with ozone in combination with UV radiation. Part I: General Principles and oxidation of tetrachloroethylene. Environ. Sci. Technol., 16: 449-453.
Sarria, V., Parra, S., Nevenka, A., Peringer, P., Benitez, N. and C. Pulgarin (2002). Recent developments in the coupling of photo-assisted and aerobic biological processes for the treatment of biorecalcitrant compounds. Catalysis Today, 76: 301-315.
Staehelin, J. and J. Hoigne (1982). Decomposition of O3 in water: Rate of initiation by hydroxide ions and Hydrogen peroxide. Environ. Sci. Technol., 16: 676-681.