Activation Of Persulfate By Naturally Occurring Iron Minerals For Degradation Of 1,1,2-TCA In Groundwater

With the rapid development of industry,groundwater is seriously polluted by chlorinated organic matter.chlorine-containing organic matter is detected in Groundwater at each country.in-situ chemical oxidation（ISCO）repair technology based on persulfate has attracted people’s attention.people pay more attention to permeable reactive barrier（PRB）and in situ reaction zone（ISRZ）.both of these technologies enhance the efficiency of persulfate oxidative degradation by adding additional activators.In this experiment,the natural iron-containing minerals in the soil and aquifers were used as activators to promote the oxidative degradation of persulfate.In the experiment,natural iron-bearing minerals hematite（Fe₂O₃）,pyrite（FeS₂）,ilmenite（FeTiO₃）,limonite（FeO（OH）·nH₂O）,siderite（FeCO₃）and magnetite（Fe₃O₄）were selected as the research object to explore Potential to activate persulfate for the degradation of 1,1,2-trichloroethane（1,1,2-TCA）.Hematite,pyrite and ilmenite can effectively promote degradation of1,1,2-trichloroethane in persulfate system.Pyrite and ilmenite have higher efficiency of activate persulfate,but due to the presence of Ferrous,a large amount of persulfate is Consumed.Hematite was selected as object because it is common in soil and lower consume of persulfate in the process.In our study,the degradation of TCA follows the first order kinetics and reaction rate constant is consistent with the concentration of persulfate.Dissolved ferric iron contributes the product of sulfate radical in persulfat e system activated by hematite.The result showed that the mechanism of hematite activation is not surface reaction in heterogeneous activation.Dichloroethylene,and acetic acid were monitored and the possible mechanism was proposed about degradation of TCA with persulfate and hematite at 48h.It shows that the dechlorination of trichloroethane in the reaction process is divided into two steps.The first step is to eliminate dechlorination to form1.1-dichloroethylene,and the second is to dechlorination t o form acetic acid.This experiment provided the basis for optimizing the ratio of hematite and persulfate to achieve the greatest degree of degradation of trichloroethane.In column experiments,the results show that degradation of 1,1,2-TCA can be enhanced by natural hematite with persulfate under dynamic flow conditions.Synthetic magnetite can activate persulfate to degrade trichloroethane under alkaline conditions and the degradation efficiency increases with the decrease of pH,while natural magnetite can only activate persulfate under acidic conditions.The reason was conducted through experiments such as XRD.The reason was that the surface of the natural magnetite contained oxides such as silica inhibited the reaction.The results of the above study indicate that the presence of hematite in the soil under natural conditions can effectively activate persulfate for the repair of chlorinated organic pollution,reduce the cost of engineering repair,and provide new ideas for in-situ chemical oxidation.