Research On The Efficiency And Mechanism Of The Degradation Of Atrazine By NTA-Fe???/H₂O₂ Complexation Fenton

Fenton/Fenton-like oxidation has been widely used in wastewater pretreatment and advanced treatment.However,the Fenton/Fenton-like method has the disadvantages of low pH,low conversion rate of Fe?III?to Fe?II?,and low utilization of Fe?II?.The complex of Fe?II?/Fe?III?with acetic acid?NTA?is more stable in neutral or weak alkaline solution,which ensures the concentration of Fe?III?/Fe?II?.Atrazine?ATZ?is a kind of refractory organic pollutant which is widely distributed in various water bodies.Fenton/Fenton-like method is one of the ideal degradation methods.In this study,complexes of NTA and ATZ were used to simulate the complex water.Firstly,the effects of NTA on degradation of atrazine in Fenton-like system were investigated:In the presence of NTA,under the conditions of moderate alkaline pH,the degradation effect of atrazine was better than that in the absence of complexing agent.Fe?NTA complexes with H₂O₂ and H₂O₂ itself are more easily decomposed due to the increase of pH value.When pH = 3?9,the degradation efficiency of ATZ increased with the increase of pH value.The degradation efficiency of atrazine is increasing with the increase of H₂O₂ dosage in a certain range.With the increase of Fe???concentration,the degradation efficiency of atrazine is higher and higher.Fe?NTA decomposes itself in the process of degradation of ATZ,and has a certain influence on the decomposition rate of H₂O₂ catalyzed by the system.Secondly,in the NTA-Fe???/H₂O₂ system,the active species were identified:Under the condition of pH = 8,the addition of tert-butanol to NTA-Fe???/H₂O₂ system inhibited the degradation of ATZ remarkably,but the excess tert-butyl alcohol could not completely inhibit ATZ,Indicating that the active species in the system have other active species in addition to hydroxyl radicals.Under the condition of pH = 8,the formation of sulfone was observed in the NTA-Fe???/H₂O₂ system when the sulfoxide was the target,which indicated that the active species in the NTA-Fe???/H₂O₂ system had high valence iron exist.The degradation of sulfoxides and the formation of sulfone under different pH conditions were further studied.The results show that the oxidized species in the NTA-Fe???/H₂O₂ system are hydroxyl radicals under acidic conditions,and the high-valent iron species exists in the oxidized active species at pH 6 to 10 under neutral and alkaline conditions.It is a reaction system in which hydroxyl radicals coexist with high valence iron.And the amount of high-valent iron increased with pH between 6?9.In the present study,the formation of sulfone in the presence of different complexing agents at pH = 8 was investigated.The results showed that no active species in the Fenton system of oxalic acid,citric acid and EDTA The existence of high-valent iron only exists in the active species of the system when NTA is used as complexing agent.