Differences Of Several Oxidants In Degradation Of Perchloroethylene And 1,4-dioxane

Groundwater organic matter contaminant has attracted more and more attention.Due to its concealment and slowness,groundwater contaminant has developed into a large area of regional pollution when it was found to be polluted.When organic contaminants leak into the ground,the quality of groundwater in this area will be affected,and the health and life safety of groundwater users will be damaged seriously.Chlorinated organic compounds are widely used organic compounds.Studies have shown that this harmful substance exists in groundwater.At present,in view of the organic contaminant of groundwater,it is urgent to take effective measures to treat and repair the polluted groundwater environment.In-situ chemical oxidation technology is considered as an effective method to control the organic pollution of groundwater.In order to solve the problems of organic chloride and its related organic contaminants,the injection method of in-situ chemical oxidation technology was used to control the related pollution.Degradation and removal of representative perchloroethylene and 1,4-dioxane by injecting oxidants into contaminated groundwater.Sodium persulfate,perxymonosulfate,hydrogen peroxide and potassium permanganate are used to remove selected target pollutants in this paper.The experimental results show that both sodium persulfate and potassium bisulfate can oxidize and remove perchloroethylene and dioxane without external activation.Potassium bisulfate can oxidize and degrade perchloroethylene in 120 hours,but only 48.6% of dioxane was degraded in 32 days.However,sodium persulfate has the opposite performance.It has a more prominent oxidative degradation performance for dioxane.In the same experimental cycle,the removal rate of dioxane reaches 93.7%,and the total removal of perchloroethylene requires 168 hours longer than that of potassium bisulfate.At the same time,the experimental results show that hydrogen peroxide is difficult to degrade organic matter without activator.The difference of oxidation degradation results of target organic compounds can be attributed to the different chemical structures of different oxidants.The different peroxide bonds in these three oxidants result in the different forms of hydroxyl radicals and sulfate radicals,which lead to the difference of oxidation degradation results of organic compounds.Further free radical quenching and electron paramagnetic resonance verify that active free radicals play a major role in the degradation of contaminants by oxidants.The different kinds of free radicals produced also lead to different oxidation degradation pathways of pollutants in the degradation experiments of perchloroethylene.Free chloride ions generated in the solution will generate relevant chlorine free radicals to accelerate the oxidation degradation of perchloroethylene.Potassium permanganate can degrade olefins by its highly efficient oxidative oxidation as a kind of oxidant without free radicals.It has good oxidative removal effect on perchloroethylene,but has little effect on cyclic organic 1,4-dioxane which can hardly promote the degradation of pollutants.