Study On The Degradation Of Atrazine By NTA-Fe(?) Activated Potassium Sulfate

The traditional Fenton advanced oxidation technology has been widely used in organic wastewater,remediation of soil and other fields.The traditional Fenton advanced oxidation technology has the shortcomings of narrow pH range,poor stability of hydroxyl radical,secondary pollution caused by the formation of iron sludge and other shortcomings.So it is limited in practical application.Advanced persulfate oxidation technology overcomes the above problems and is an efficient and oxidative pollutant treatment technology emerging in recent years.The action mechanism of the persulfate system is that the persulfate is activated by the heat,visible light,transition metal ions,alkali substances,phenols,quinones and the like to generate the sulfate radical(SO4-)with oxidation activity,sulfate free radicals(SO4.-)have the characteristics of strong oxidizing power,long living life and no selectivity to organic pollutants such as pollutants in the degradation reaction system.In this study,atrazine(ATZ),a refractory organic pollutant,was selected as the target pollutant.The effects of reaction system of ferric potassium monoxide(PMS)activated by ferric ion on the degradation of atrazine were investigated.The reaction mechanism and the intermediate degradation products of ATZ were also investigated.In this study,we firstly investigated the degradation of atrazine(ATZ)in Fe(?)activated potassium monosulfate(PMS)system.The effects of potassium persulfate concentration,Fe(?)concentration,pH and reaction temperature on the degradation of ATZ were studied.The effects of coexisting substances(C1-,SO4-,NO3-,HA)in naturally occurring water on the degradation of ATZ were also analyzed.The results showed that under the condition of pH = 3,the degradation of ATZ was enhanced with the increase of PMS concentration and Fe(?)concentration within a certain range.The degradation rate of ATZ was only 50%under the optimal conditions.At pH=7,the degradation of ATZ decreased with the increase of Fe(?)concentration within a certain range.In Fe(?)/PMS system,ATZ degraded better under acidic and neutral conditions.Coexisting substances in natural water have inhibitory effect on the degradation of ATZ in Fe(?)/PMS system.The inhibitory effect is as follows:HA>SO4->Cl->NO3-.Then,to improve the degradation of atrazine by Fe(?)/PMS system,metal complexing agent was added to the reaction system.In this study,it was found that the degradation efficiency of ATZ in Fe(?)/PMS system increased greatly after adding NTA,and the degradation effect of ATZ increased within a certain range with the increase of potassium sulfate concentration and Fe(?)concentration.When the molar ratio of NTA and Fe(?)is 2,ATZ has a better degradation effect.Excessive NTA consumes sulfate radical instead,which further reduces ATZ removal rate.The degradation of ATZ by NTA-Fe(?)/PMS was better under neutral and weak alkaline conditions.The addition of NTA in the acidic range did not promote the degradation of ATZ.The coexisting substances Cl-?SO4-and NO3-in natural water had no effect on the degradation of ATZ in the NTA-Fe(?)/PMS reaction system at a certain concentration range.High concentrations of HA inhibited the degradation of ATZ to a certain extent.However,HA content in water is about a few milligrams to a dozen milligrams,so we can ignore the impact of humic acid.Methanol and t-butyl alcohol were used as free radical scavengers to identify the oxidation active species of the reaction system.Under different pH conditions,the types of oxidized active substances in Fe(?)/PMS system were different.Under the condition of pH = 3,the contribution of sulfate radical to oxidative system was larger.Under the condition of pH = 8?the sulfate radical and the hydroxyl radical play the same role of oxidation.In the NTA-Fe(?I)/PMS system,the experiments of free radical scavengers show that there are not only sulfate radical and hydroxyl radical in the system,but also another oxidizing active substance,namely high valence iron(Fe(IV)).Four kinds of degradation intermediates,CDIT,DEA,DIA and DEDIA,were mainly detected by liquid chromatography.Among them,CDIT is the product of dehydrogenation of ethyl on ATZ side chain structure.DEA and DIA are the result of ATZ being attacked side chain to remove ethyl and isopropyl on nitrogen.DEDIA is the product of further oxidation of DEA and DIA.