Study On The Degradation Of Atrazine And Its Recalcitrant Photodegradation Product Under Electron Beam

As a widely used herbicide, atrazine exists in surface and ground water, and belongs to an environmental endocrine disruptor. Atrazine has toxicity and poisoning action on the ecological environment and human. Previous researchers find that, in the process of photodegradation of atrazine, the atrazine degradation ends with cyanuric acid. And in the aquatic environment, cyanuric acid and melamine coexist, the the ecological environment of the toxicity will be significantly enhanced. Therefore, it becomes an urgent and critical task to take effective degradation of atrazine mineralization and their photodegradation products cyanuric acid become an urgent and critical task.In this paper, atrazine could be compeletly mineralized without any cyanuric acid residues by electron beam irradiation. The degradation of atrazine follow the pseudo-first-order reaction kinetics. In pure water, the degradation rate of 6mg/L atrazine reaches more than 90% at low irradiation doses 0.5k Gy. At the same time, a lot of chloride ions releases from atrazine and chlorine ion conversion rate reaches 85%. In the process of UV photodegradation atrazine, the concentration of cyanuric acid relaesed from 6mg/L atrazine increases to 0.8mg/L and after 100 h ultraviolet irradiation, no signs of cyanuric acid degradation is observed. Howerer, in the process of electron beam degradation of atrazine, from 0 to 20 k Gy, the concentration of cyanuric acid generated from 6mg/L atrazine increases and reaches the maximum 3.14mg/L, while from 20 k Gy to 60 k Gy, cyanuric acid released from atrazine gradually degrades and drops to 0.37mg/L. In different electron beam irradiation atmosphere, the comparation of cyanuric acid degradation effection shows as follows: the reducing atmosphere is the best, next is oxidation-reduction atmosphere, while the oxygen atmosphere is the worst. Besides, in the process of atrazine and cyanuric acid electron beam degradation, the hydrated electron plays an important role.In the process of atrazine electron beam irradiation degradation, the possible degradation pathway and mechanism is proposed: hydrated electron will transform chlorine of atrazine into chloride ion, alkyl chain could be oxidized into formic acid by hydroxyl free radical, then two formic acids could be combined into oxalic acid. And amino side chains not only can be transformed into nitrate by hydroxyl free radical, but also can be transformed into ammonium ions by hydrated electron. With the increase of irradiation dose, atrazine electron-deficient benzene nitrogen ring could be attacked by hydrated electron. And accompanied with the formation of ammonium ions, the carbon in the benzene nitrogen ring is converted into formate. Then two formic acids combined into oxalic acid.In the process of cyanuric acid electron beam irradiation degradation, the possible degradation pathway and mechanism is also proposed: electron-deficient benzene nitrogen ring could be attacked by hydrated electron. And accompanied with the formation of ammonium ions, the carbon in the benzene nitrogen ring is converted into formate. Then two formic acids combined into oxalic acid.Therefore, electron beam irradiation can mineralize atrazine and its photodegradation product cyanuric acid. Then atrazine and cyanuric acid is transformed into inorganic ions and small organic molecules. Compared with advanced oxidation technologies, especially photodegradation, electron beam is an effective and safe method to remove atrazine and its photodegradation product cyanuric acid.