Strategies For High Efficient Redox Removal Of Typical Aqueous Atrazine Herbicides And Its Mechanism

As a source of life,water is closely related to human life.In recent years,water resource in China has been polluted seriously due to the abusing pesticides.So it is imperative to seek a method of high efficiency,low energy consumption,and low second-pollution for remediation of aqueous organic pollutants.Advanced oxidation technology(AOT)has drawn more and more attentions,recently,on the base of the stimulation including of light,sound,electricity and magnetism,reactive oxygen species with strong oxidizing performance generated in AOT process can degrade or even mineralize refractory organic pollutants,into water and carbon dioxide.In this study,triazine herbicide which had been widely used and were hazardous to human beings and the environment,were used as model organic pollutions.The strategies for high efficient redox removal of the typical atrazine herbicides have been designed,and the mechanism was investigated in detail.The main content includes the following two aspects:In the first section,we developed an aerobic zero-valent iron and potassium dihydrogen phosphate molecular oxygen activation system(Fe/KH2PO4)to high efficiently degrade atrazine in aqueous solution.The results showed that atrazine degradation rate in this process was strongly depend on the presence of potassium dihydrogen phosphate,atrazine degradation increased with increasing the amount of potassium dihydrogen phosphate added,the surface bound ferrous content on the surface of iron increased greatly in the course of the Fe/KH2PO4 process;the oxidative atrazine degradation efficiency and rate constants highly depended on the surface ferrous content;it was supposed that phosphoric acid could coordinate with hydroxyl species on the surface of the iron powder,leading to multi-layer ferrous ion and phosphate complex interface,which subsequently provided enough ferrous ion to catalytically initiate Fenton reaction for realizing the oxidative degradation of atrazine.In the second section,we constructed a sodium thiosulfate dechlorination process to quickly degrade atrazine in solution,the mechanism of the reaction between sodium thiosulfate and atrazine was studied in detail.The results showed that the sodium thiosulfate can quickly react with atrazine to generated the hydroxyl dechlorination intermediates.Compared with atrazine,the intermediate generated were of lower toxicity.Besides atrazine,other herbicides with triazine-ring could also be efficiently degraded in the sodium thisoulfate process.DFT calculation results indicated that protons could initiate the dechlorination under acid condition,followed hydroxyl dechlorination process.