Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2008.140.145FarooqRobinaShaukatS.F.KhanAbida K.FarooqUmar1200881A cost effective method of decomposition was developed for industrial effluents by using ultrasound in combination of H_{2}O_{2}. The process was optimized by studying the decomposition of methidathion pesticide at different frequencies, different ultrasonic wave amplitudes, pH and concentrations of the solutions. It was shown that the rate of sonochemical decomposition was directly linked to the OH^{°} availability in the solution. The degradation was more efficient for the higher frequency because the rates of OH^{°} formation in water saturated with air were more at higher frequency. It was observed that higher the ultrasonic frequency, higher was the energy consumption. This problem of higher energy consumption was resolved by increasing the concentration of H_{2}O_{2}. Ultrasound/H_{2}O_{2} process gave better decomposition than ultrasound alone. Decomposition of methidathion was effective with ultrasound at greater sound wave amplitude. When the pH was controlled below the pk value of methidathion, significantly better decomposition of methidathion resulted. The decomposition of methidathion appeared to follow first-order reaction kinetics. The reaction rate constant (k) was greater at smaller pH and there is an exponential relation between them.]]>Andrew, P.E., S.C. Lenore, W.R. Eugene and E.G. Arnold, 2005Petrier, C., L. Marie-Francoise, F. Anne, B. Abdallah, D. Bernard, R. Viviane and G. Nicolas,1994Christen, P. and F. Anne, 1997Devinder, M., T. Elizabeth, Papish and P. Kaumudi, 2004Farooq, R., F. Lin, J.J. Huang, S.F. Shaukat and S.M. Mukhtar, 2002Farooq, R., L. Feng-kai, S.F. Shaukat and J.J. Huang,2003Hilla, S. and N. Nava, 2005Hua, I. and E.J. Thompson,2000Koteonarou, A., G. Mills and M.R. Hoffmann, 1992Koteonarou, A., G. Mills and M.R. Hoffmann, 1996Mason, T.J., 1990Misik, V., N. Miyoshi and P. Riesz, 19952O/D_{2}O mixtures: Probing the temperatures of cavitation regions.]]>Okouchi, S., O. Nojima and T. Arai, 1992Pandey, A.D., K.K. Mallick and P.C. Pandey, 1980Sun, J., S. Sun, J. Sun, R. Sun, L. Qiao, H. Guo and M.H. Fan, 2007Wang, J., Z. Pan, Z. Zhang, X. Zhang and F. Wen et al.,2006