Sulfite Promoted Photodegradation Of Atrazine And 4-Chlorophenol

Water is the source of life. Nowadays, with the economic development, a great quantity of contaminants were drained into the environment. Photodegradation is one of the most important transfer ways of organic pollutants in nature and natural photosensitizer like hydrogen peroxide, sulfite could promote this process.The photosensitive property of sulfite is owning to the highly reactive species (e.g., eaq-, H·; SO3·-) generated in sulfite activation of ultraviolet irradiation. Rapid elimination of halide ion was observed in the reaction between hydrated electron with organic molecules contain substituent halogen atoms. The hydrogen atom reacts with organic compounds by abstracting H from saturated molecules and by adding to centers of unsaturation. Hydrated electron and hydrogen atom are both species with high reducibility. Reductive degradation happens rapidly by this photochemical strategyWe first investigated the effects of sulfite on UV irradiation degradation of atrazine. By examining the degradation rates and products in these processes, we found that the generated hydrated electron and hydrogen atoms can not only promote the photodegrdation of atrazine, but also realize the cleavage of its s-triazine ring through altering the photochemical atrazine degradation pathway. Only dechlorinated hydroxylated products generated in direct atrazine photodegradation, while, dechlorinated hydrogenated mainly happened in the presence of sulfite. Meanwhile, the photochemical degradation of 2,4-diamino-1,3,5-triazine (AAT) in the presence of sulfite produced ammonium ions and small molecule acids, confirming the cleavage of s-triazine ring during this sulfite promoted photochemical treatment.We subsequently studied the effects of sulfite on the photodegradation of contaminant under conditions more like nature. We used xenon lamp as the light resource and 4-chlorophenol as the target pollutant. By the detection of degradation intermediates, we found that the addition of sulfite can also promote the 4-chlorophenol degradation, and changed the degradation pathways. The main intermediate was changed from hydroquinone to phenol and hydroquinone was reduced to 4-hydroxycyclohexanone and 1,4-cyclohexanedione, either. More intermediates with lower toxicity were generated.In summary, this thesis clarified the effects of sulfite on promoting photodegradation of atrazine and 4-chlorophenol. The reactive species generated in this process can promote the degradation and also change the photochemical degradation pathways of these two pollutants. The stable structure in atrazine and 4-chlorophenol, s-triazine ring and benzene ring, were broken in this photochemical process with sulfite. These studies help us to understand the photodegradation processes of atrazine and 4-chlorophenol that may really happen in nature, and also provide a new method in photodegradating organic pollutant.