Application of Activated Persulfate Oxidation Method in Degradating DDT in Field Contaminated Soil

This paper evaluated the use of Fe2+ activated sodium persulfate oxidation method to remedy DDT-contaminated soil from a typical former organochlorine pesticide field in the Yangtze River Delta.The influence of different factors on the target pollutants removal efficiency was studied,including the initial pH and mineral coupling factor,sodium persulfate/Fe2+ concentration ratio factor and oxidant concentration factor.Results showed that the magnetite and hematite,when adding to slurry system with only sodium persulfate,could significantly improve the degradation of DDTs rate(P 0.01) under the acidic and neutral condition,and the DDTs degradation rate at pH 3.2 was higher than when pH was 7.7.Due to high ferrous content of zero-valent iron and siderite,Fe2+ concentration nearby mineral surface was excess and Fe2+ would react with sulfuric radical,thereby lowering the DDTs oxidation efficiency.The optimal persulfate/Fe2+ ratio in this slurry system was found to be 20︰1 at pH 3.2,while the most effective in degrading DDTs was more than 90% within 24 h.At the same time,results of DDT oxidation by six kinds of oxidants including Fe2+ catalyzed sodium persulfate,sodium persulfate,Fenton reagent,hydrogen peroxide,double oxidation reagents(mixture of activated persulfate and hydrogen) and potassium permanganate were compared,and evaluated the advantages and disadvantages of different oxidants.DDTs oxidation efficiency and rates by six oxidants followed degrading sequence of Fe2+ catalyzed sodium persulfate sodium persulfate Fenton reagent double oxidation reagents permanganate hydrogen peroxide at pH 3.2.This study indicated that the application of activated persulfate oxidation is a feasible method to treat soil contaminated by DDT,which is suitable in remediation applications.