The Fundamental Study On Degradation Of DMMP And CEES By Ozonization Advanced Oxidation Technologies

It is a strategic problem to cope with desertion chemical weapons and chemical terrorist attacks for the defense construction and the national economy and the people’s livelihood. Therefore,the development of new,efficient and fast methods to deal with chemical warfare agents is very important and urgent.In this study Dimethyl Methylphosphonate（DMMP） and 2-Chloroethyl Ethyl Sulfide（CEES） were selected to be the simulants of chemical warfare agents. The degradation effects,degradation mechanism and degradation kinetics of chemical agent simulants by ozone and ozone/catalysts were investigated respectively.The above results were obtained.（1） The research results of the degradation of chemical agents by ozone show that ozone could effectively degrade DMMP.Initial pH value can significantly affect the degradation of DMMP. The strong alkaline condition is beneficial to the degradation of DMMP.The degradation efficiencies of DMMP would improve with the increase of oxygen concentration.With the increase of initial concentration the degradation efficiencies of DMMP would increase.The degradation efficiency of DMMP improves with the raise of temperature.When temperature is beyond 50℃the influence of temperature on degradation efficiency of DMMP weakens.There is a positive correlation between the degradation efficiency of DMMP and ozone flow.When ozone flow is over 400ml/min the influence of ozone flow on degradation efficiency of DMMP weakens. The reaction conditions of DMMP degradation were optimized by orthogonal experiments.In optimum conditions the DMMP degradation efficiency can reach 81%after being treated for 3 min.Variance analysis results show that initial pH value significantly influence the degradation of DMMP.Free radical inhibitor can effectively inhibit the degradation of DMMP by ozone.Indirect reaction of free radical is the main cause for the degradation of DMMP.In alkaline condition ozone can be decomposed by OH^- to form hydroxyl radical,which can attack the function groups of DMMP to start the degradation reaction.The reaction would generate some intermediates,and then some small molecular substances,such as alcohol,aldehyde and acid,would be formed. Finally,these small molecular substances would probably be mineralized.Three reaction pathways are predicted for the DMMP degradation by ozone.The pathway 1 starts with the dehydrogenation reaction of DMMP by·OH.The pathway 2 starts with the hydration of DMMP and water,and the pathway 3 starts with the addition-elimination reaction of·OH and DMMP.All of the above three reaction pathways can mineralize DMMP to generate PO₄^3-,CO₂ and H₂O.The reaction pathways of DMMP by ozone are proved by quantum chemistry,and the thermodynamics support the proposed degradation pathways of DMMP by ozone.The kinetics study results show that the reaction is apparent zero order kinetic reaction in acid condition,and it is apparent first order kinetic reaction in alkaline condition.Initial pH value,ozone concentration,temperature,DMMP concentration and ozonation gas flow can influence the degradation kinetics of DMMP by ozone.（2） CEES can be degraded effectively by ozone.Neutral condition is benefical to the degradation of CEES.The degradation efficiencies of CEES improve with the increase of ozone concentration.At the range of relatively low ozone concentration the increase of ozone concentration affect the degradation of CEES obviously.The degradation efficiency of CEES decreases with the increase of initial concentration.But its absolute degradation amount improves with the increase of the initial concentration.With the rise of the temperature the degradation efficiency of CEES improve.When the temperature is beyond 50℃the influence of temperature on degradation efficiency of CEES weakens.The degradation efficiency of CEES increase with the increase of ozonation gas flow.When the ozonation gas flow is beyond 400ml/min the influence of ozonation gas flow weakens.The reaction conditions of CEES degradation are optimized by orthogonal experiments.In optimum conditions the CEES degradation efficiency can reach 95%after being treated for 3 min.Variance analysis results show that initial pH value significantly influence the degradation of DMMP.Free radical inhibitor can effectively inhibit the degradation of CEES by ozone.Indirect reaction of free radical is the main cause for the degradation of CEES.Ozone can be decomposed to form hydroxyl radical,which can attack the function groups of the CEES through dechlorination,dealkylation and substitution to start the degradation reaction.Some intermediates,such as acetyl chloride,dimethyl sulfone and carboxylic acids would be formed.Finally,these small molecular substances would probably be mineralized.Four reaction pathways are predicted for the CEES degradation by ozone.The reaction pathways of CEES by ozone are proved by quantum chemistry,and the thermodynamics support the degradation pathways of CEES by ozone.The kinetics study results show that the degradation reaction of CEES by ozone is apparent first order kinetic reaction.Initial pH value, ozone concentration,temperature,CEES concentration and ozonziton gas flow can influence the degradation kinetics of CEES by ozone.（3） The catalysts can significantly improve the treatment effect of chemical agents simulants by ozone.The selection experiments of catalysts show that the catalytic effect of Fe²⁺ is the best. Compared with the individual ozone oxidation,the degradation efficiencies of simulants by Fe²⁺ catalytic ozone oxidation improve.When the addition quantity is 5mmol/L the degradation effects of simulants are the best.Initial pH value significantly affect the degradation of simulants by catalytic ozone oxidation.The strong alkaline conditions are beneficial to the degradation of DMMP and CEES.The degradation efficiencies of DMMP and CEES improve with the increase of ozone concentration and ozonation gas flow.The degradation rate of simulants would decrease with the increase of initial concentration.But the absolute degradation amount of simulants improve with the increase of the initial concentration.With the rise of reaction temperature the DMMP degradation rate increases first and decreases afterwards,and that of CEES would increase with the rise of temperature.The reaction conditions of simulants degradation are optimized by orthogonal experiments.In optimum conditions the degradation efficiency of DMMP can reach 93%after being treated for 3 min,and that of CEES is 97%.Variance analysis results show that initial pH value significantly influence the degradation of DMMP,and initial concentration significantly influence the degradation of CEES.The kinetics study results show that the degradation reaction of DMMP and CEES by catalytic ozone oxidiation are apparent first order kinetic reactions.Initial pH value,ozone concentration,temperature,CEES concentration and ozonziton gas flow can influence the degradation kinetics of CEES by ozone.