Desorption Kinetics Of Thermal Enhanced Soil Vapor Extraction（T-SVE） Technology Used In Hydrocarbon Contaminated Soil

The problem of hydrocarbon contaminated soil is becoming more and more serious.Scholars are eager to study remediation technology.Whether in experiment or actual remediation,the technology developed has greatly promoted the treatment of hydrocarbon contaminated soil.Thermal enhanced soil vapor extraction（SVE）was used to treat hydrocarbon contaminated soil.The effects of ventilation rate,gas water content（GWC）of the extracted gas and soil water content（SWC）on the efficiency of thermal enhanced SVE were studied.The LDF and Freundlich model were used to fit the soil desorption isotherms.Research for the effect of modified soil on the removal rate of hydrocarbon pollutants.The results showed that when the treatment temperature was 120oC,the optimal treatment process was 80 m L/min of ventilation rate,15%GWC in the extraction gas,10%SWC,and the processing time was significantly shorten.The aeration rate was reduced from 40 m L/min to 80 m L/min,the processing time was shortened from 425 min to 350 min,and the water vapor concentration in the extracted gas increased from 0%to 15%,and the processing time was shortened from 350 min to105 min.The GWC was increased from 15%to 25%and the treatment time was prolonged from 105 min to 240 min.When the soil moisture content is 10%,the heat strengthening processing time was shortened to 290 min.Among the modified soils,k decreased from 0.01487 to 0.00283 and the desorption rate remained around 99%as acid modified soil with short desorption time（from 330 to 270 min）.At the end of remediation in the acetic acid modified soil,the average concentration of pollutants was reduced from 127569 to 848 mg/kg,corresponding to 99.3%of mass removal.Compared with the experimental data,the results showed that the LDF equation was suitable for fitting under a simple condition（ventilation rate）.The Freundlich equation was more suitable for fitting complex system（soil-water-gas）.Different from the traditional soil column model experiment,an experimental study was made on the factors affecting the remediation of hydrocarbon-contaminated soil by the T-SVE method,and fit the kinetic equation of thermal desorption to get the best parameters of the remediation of hydrocarbon-contaminated soil.The results of single factor experiments showed that the optimum temperature,rate,SWC and the optimum soil contamination content were 90oC,70 m L/min,4%and 3300 mg/kg.Four thermal desorption kinetics equations were used to fit.However,according to the kinetic constants and R~2 values of the fitting results,the optimum gas extraction rate was 50 m L/min,the optimum soil contamination content was 3800 mg/kg,and the other conditions were the same.Considering the correlation between the factors,through response surface and matrix analysis experiments,it showed that the T-SVE method had the best effect on the treatment of hydrocarbon-contaminated soils when the gas phase extraction temperature was 70oC,the gas extraction rate was 40 m L/min and the soil moisture content was 5%.The degree of influence was extraction temperature>extraction rate>SWC.The experimental results of removal efficiency of different hydrocarbon pollutants showed that the T-SVE method had the best effect on the removal efficiency of multi-component hydrocarbon-contaminated soils.The removal rate of soil was higher than that of single component.