Soil Labile Iron Preparation And Oxidation Of Oil Contaminated Soil

In the traditional Fenton chemical oxidation of oil contaminated soil processes, the hydroxyl radicals were produced in the aqueous phase, the oil must be parsed from the soil solid phase to the aqueous phase to be oxidized, however the labile iron Fenton system uses modified Fenton’s reagent(citric acid system) to combine the added Fe2+ with the organics in soil to form a labile iron in soil solid phase. In this way, hydroxyl radicals will be generated in the solid phase and oil in contaminated soil can be directly oxidized so that oxidation effect will be improved. This paper examines the content of labile iron Fenton system under different initial pH, iron concentration, hydrogen peroxide concentration of the reaction system conditions and the oxidation effect of oil-contaminated soil, this paper also ascertains the optimum conditions of producing soil labile iron, analyzes the source of labile iron and further studies the production of hydroxyl radicals in labile iron Fenton system and the oxidation effect of contaminants in soil, which provides a theoretical basis for on-site remediation of petroleum contaminated soil under labile iron Fenton system. The conclusions are as below:(1) Soil properties have a great impact on the labile iron content of the soil. When the soil organic matter(SOM) content was high and the natural iron content was low(for soil S2, SOM content was 10.6%, natural iron content was 26.5 mg/g), the labile iron content was up to 4.65 mg/g after 1100 mmol/L H2O2 was divided into equal four doses added; For low SOM content and high natural iron content soil samples(for soil S3, SOM content was 3.9%, natural iron content was 48.0 mg/g), the labile iron content was only 3.75-3.90 mg/g after 1100 mmol/L H2O2 was divided into equal six doses added.(2) For the soil S2 and S3, when the initial pH of the reaction system was 7.05~7.40, the Fe2+ concentration was 2.9 mmol/L, the labile iron content were 3.9 mg/g, which higher than the labile iron content(0.3-3.3 mg/g) when the initial Fe2+ concentration was 5.8 mmol/L. When the initial Fe2+ concentration was 5.8 mmol/L and the H2O2 concentration was 1100 mmol/L, the labile iron content of soil S2 and S3 were 3.3 mg/g and 1.8mg/g, which was higher than the labile iron content(1.8 mg/g, 1.0 mg/g) when H2O2 concentration was 700 mmol/L. This indicates that it was conducive to the formation of soil labile iron when a high concentration of H2O2 was added.(3) Iron(manganese) oxide bound iron accounted for 83%-94% in the soil labile iron, which was 2.4-3.8 times of the natural soil. It can produce 4.7×10-15~6.3×10-15 mol hydroxyl radicals When the soil labile iron was 2.4-3.0mg/g and 900 mmol/L H2O2 was added one time, which increased by 5.8 time than the system without soil labile iron.(4) When the soil contains labile iron, 900 mmol/L H2O2 was added one time, it have 44%, 62%, 33% TPH were removed in three kinds of oil-contaminated soil, compared with the soil without labile iron control group increased by 29%, 26%, 25.5%, indicating that soil labile iron improve the oil oxide effect in the soil. Further study found that SOM was closely relate with the role of soil labile iron, TPH removal rate was less than 3%, when the soil without SOM, compared with the soil containing SOM low 7%, indicating that when the soil without SOM, the formed iron in the soil can not catalyze H2O2 oxidized petroleum in soil.(5) TPH removal rate was only 4%, when the long chain hydrocarbons(C21-C30) content was 60.0% in the soil, while the short chain hydrocarbons(C11-C20) content was high(66.5%), TPH removal rate was up to the 35%, indicating that short chain hydrocarbon more easily oxidized removal than the long-chain hydrocarbon.(6) For the soil S3, the initial pH of the reaction system was 7.20, Fe2+ concentration was 2.9 mmol/L, 900 mmol/L H2O2 was added one time, TPH removal rate was higher(36.1%), and the C26-C30 long carbon chain degradation rate was 37.1%.