The role of UV‐irradiation pretreatment on the degradation of 2,4‐dichlorophenoxyacetic acid in water

Abstract

The degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in water by the combination process of UV-irradiation, humic acids and activated sludge treatment has been studied. The photoreaction rate of all irradiated samples was lowest for the sample irradiated at 308 nm (the XeCl excilamp) in the absence and in the presence of humic acids, and highest for the sample irradiated at 222 nm (the KrCl excilamp). Photolysis of 2,4-D has been shown to enhance the subsequent microbial degradation.

Photosensitized Reactions of Psoralen and Herbicides Revealed by the Pump-Probe Method

“…It has the absorption band in the region of 370 nm. It seems likely that the intermediate product that absorbs in the long-wavelength range 600-800 nm can be attributed to the formation of a hydrated electron during two-step photoionization [10]. Analogous intermediate products were observed for herbicide photolysis in the presence of 8-MOP.…”

“…Upon laser illumination by light at 266 nm, the intensities of bands in the absorption spectra in the region of 250 nm and 310 nm increase (Fig. 2), which can be attributed to the absorption of newly formed quinone and lactone photoproducts, respectively [10]. The newly formed photoproducts act as photoinductors for further phototransformations of herbicides rather than are accumulated in the solution [3].…”

“…4b). It is well known [10] that the triplet 8-MOP state is formed upon single-quantum excitation. It has the absorption band in the region of 370 nm.…”