The use of gamma radiation for removal of pesticides from waste water

In the present study, a try was made to explain the degradation kinetics du e to irradiation of aqueous solutions of some active ingredient pesticides. These pesticides are as follows: one type of triazine herbicide Ametryn an d one type of carbamate insecticide (Applaud) and two types of chlorinated organic pesticides, Aldrin and Chlorothalonil. Factors affecting the radiol ysis of these pesticides such as the pesticide concentration, irradiation d ose, dose rate and pH of the solutions were studied. Ametryn, Applaud, Chlo rothalonil and Aldrin insecticides were degraded by gamma-radiation and in the case of the chlorinated pesticides hydrochloric acid was detected. The pH effect has proved to vary according to the type of the pesticide and lit tle degradation was observed in alkaline medium, while more degradation of the pesticides in the neutral medium was observed depending on the type of pesticide and on its chemical structure. However, the degradation in the ac id medium was even higher. A drop in pH was observed and may be attributed to the degradation of the pesticide molecules to lower molecular weight com pounds, such as organic acids. A combined treatment of gamma irradiation an d conventional methods was applied and the effect of different additives su ch as nitrogen and oxygen showed that nitrogen did not enhance the degradat ion, while an enhancement in the degradation process was observed when oxyg en was added. Experiments on the adsorption of these pesticides on certain polymeric materials and on Granular Activated Carbon (GAC), showed that GAC has the highest adsorption capacity. It may be concluded that the radiatio n degradation followed by adsorption of the toxic pesticide pollutants and their removal from wastewater down to concentrations not exceeding the maxi mum permissible concentration (MPC), according to international standards, proved to be better than the conventional methods of purification.