Elimination of highly consumed herbicide; 2,4-dichlorophenoxyacetic acid from aqueous solution by TiO 2 impregnated clinoptilolite, study of degradation pathway

Abstract In this research, the degradation of the highly consumed herbicide, 2,4-dichlorophenoxy acetic acid, was evaluated by a nanophotocatalyst prepared by impregnation of natural zeolite clinoptilolite with TiO 2 . The photodegradation process of was studied under UV and visible light irradiations. To optimize the influencing parameters on the degradation efficiency, the Design Expert software and the Response surface methodology were used. The predicted values obtained by the methods were in good agreement with the experimental data. The degradation efficiency determined by UV‐Vis spectroscopy indicated that the optimized degradation efficiency (58% by UV, and 31% by visible light) was obtained at pH = 6, catalyst dose of 0.4 g L −1 , pollutant concentration of 6 mg L −1 , and irradiation time of 95 min. The reaction mechanism was studied by Gaussian 03 program and a computer simulation method (density functional theory). The results were in good agreement with the results of the HPLC method used for identification of the degradation products. The mineralization of the pollutant was evaluated by measurement of total organic carbon of the degradation solution before and after irradiations. The results indicated that the degraded pollutant was mostly mineralized and converted to of CO 2 and H 2 O.