Model applications and intermediates quantification of atrazine degradation by UV-enhanced fenton process

Degradation of the herbicide atrazine (ATZ) by the UV-enhanced Fenton process (UV-FP) was investigated. An enhanced photochemical effect was observed in the process compared with the simple combination of the two individual reaction rates of sole-UV (UV radiation) and dark-FP (sole Fenton's process). Accordingly, a photochemical model based on the two parallel reactions was proposed to predict the reaction kinetics of UV-FP, where two rate enhancement factors were adopted and found to be capable of successfully describing the rate improvement. In addition, the transformation pathway of ATZ decay was successfully investigated by using novel technology, liquid chromatography- electrospray tandem mass spectrometry (LC/ESI-MS/MS). Fourteen intermediates were identified in the process. The alkylic oxidation followed by dealkylation and/or dechlorination-hydroxylation was found to be the major pathway of the decay of ATZ in UV-FP. All of the detected intermediates were found to be dealkylated in different levels or positions. The dealkylated species were found to be further dechlorinated. The chlorinated products reduced to 17% of total, whereas the dechlorinated products remained at 73% and were further decayed after 60 min of treatment. In view of the gradual reduction of the mass balance of the total s-triazine, this suggested that a ring cleavage may occur on the ATZ in the UV-FP.