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The kinetic of photo catalytic degradation of Congo red dye using semiconductor in aqueous solution of ZnO has been studied. All photochemical experiments have been carried out in quartz photo cell 25ml capacity and the solvent used for all experiment was distilled water (D. W). The influence of temperature has been investigated as well. Spectrophotometric method was utilized for this work. Degradation kinetic has been done for absorption peak of Congo red at 497 nm and 344 nm. Different method was applied for this purpose, and the results show that the degradation of Congo red was first order at 497nm and zero order at 344 nm. The degradation of CR dye were increased by increasing temperature from 20 oC to 40 oC and then degreased at 50 oC and this is due to desorption that occur at the semiconductor surface while; in case of 10 oC the rate constant was higher than 20 oC. However, when changing the concentration the rate constant dose not changed regularly, this perhaps due to the fact that it does not follow the same order throughout the degradation process, and it does not obey Arrhenius law of activation energy.

In this paper, we investigate the existence, uniqueness, and stability of the periodic solution for the system of nonlinear integro-differential equations by using the numerical-analytic methods for investigating the solutions and the periodic solutions of ordinary differential equations, which are given by A. Samoilenko.

photocatalytic degradation of fungicides (chlorothalonil) in suspension aqueous solution with semiconductors (tio­2, zno) and without semiconductor has been investigated. the influence of different parameters such as light sources, the concentration of fungicides, type of semiconductors and temperature were studied by uv-visible spectrophotometer at 232 and 254 nm. the degradation reaction order spectra of chlorothalonil were determined which first order at 232 nm and second order at 254 nm. in addition, the rate constant, arrhenius factor and energy of activation can be estimated for both peaks. moreover, conductivity of chlorothalonil has been recorded during the photo-degradation and the rate of reaction also has been determined that dependent on product formation.

In this paper we study the periodic solution of nonlinear system of differential equations depending on the gamma distribution by using the numerical analytic method to investigate periodic solutions of ordinary differential equation which given by Samoilenko A. M. .These investigations lead us to improving and extending this method. Also we expand the results gained by Samoilenko A. M. to change the periodic system of nonlinear differential equations to periodic system of nonlinear differential equations depending the on gamma distribution.