Fe₃O₄-based Activated Persulfate For The Degradation Of Organic Contaminants In Groundwater

Groundwater is very important for the development of human.While,due to the industrialization of world,many countries in the world suffer from varying degrees of pollution in groundwater has made threating to Human's survival and development.Nowadays,the remediation of polluted groundwater has become the world issues of common concern.In recent years,more and more researchers committed to the restoration of contaminated groundwater,more and more techniques have been proposed and implemented.Bioremediation methods and chemical remediation methods are the most commonly method for groundwater remediation.Although bioremediation methods have the advantage of cost-efficiency and operation-easy for the remediation of contaminated groundwater,bioremediation methods needed to harsh environmental conditions and cannot be widely used in many sites.Chemical remediation method is a hot spot of research for pollution of groundwater.Advanced oxidation is one of chemical remediation methods.Most organic compounds can be oxidized by free radicals.Hydrogen peroxide and permanganate have been concerned for degradation organic contaminants.Persulfate,which can produce sulfate radical with strong oxidation,and can be more stable(compared with hydrogen peroxide),causes increasing attention of scholars.Sodium persulfate was selected as oxidant in this study.The suitable transition metal oxide was selected for activating persulfate.In this study,Fe3O4 was first selected from eight transition metal oxides(MnO2,MnO,Fe3O4,Fe2O3,CuO,Cu2O,CoO,NiO)due to its higher effectiveness in activating persulfate to degrade 1,2-dichloropropane(1,2-DCP).Then the study is focused on using Fe3O4 to activate persulfate for degradation of 1,2-DCP and other refractory contaminants in heterogeneous systems.The results of persulfate-based degradation of 1,2-DCP,1,1,2-trichloroethane(TCA),1,4-dioxane,and methyl tert-butyl ether(MTBE)show that the presence of Fe3O4 significantly enhanced degradation of all four contaminants.The four contaminants could be degraded completely in similar time periods(?72 h),indicating non-selectivity of the Fe3O4-activated persulfate for contaminants.Production of soluble Fe was insignificant before depletion of the contaminants,showing that degradation of contaminants is preferential to reaction between persulfate and Fe3O4.Increasing the oxide-solid/liquid ratio in the system resulted in an increased degradation rate of 1,2-DCP and faster production of chloride.A decrease in concentration of persulfate caused an increase of the degradation rate.Degradation of contaminants and production of chloride,sulfate,and soluble Fe all follow zero-order reaction kinetics.Results of the electron paramagnetic resonance test and isopropanol-interfered degradation test show that the reaction is radical based.A surface reaction mechanism was proposed for contaminant degradation in the system,with production of radicals at the surface as the rate-limited step.The results of this study indicated the potential of application of the persulfate-Fe3O4 method for remediation of groundwater contaminated by organic compounds.And the great potential of Fe3O4 in enhancing persulfate-based in situ chemical oxidation for remediation of sites contaminated by recalcitrant organic compounds.