Experimental Research On Remediation Of Low Permeability Organic Contaminated Soil By Surfactant-enhanced Air Sparging

Surfactant enhanced air sparging remediation technology has been proved to be effective in removing organic pollutants in medium and high permeability soil.In order to expand the application scope of the Surfactant enhanced air sparging remediation technology and obtain the effect of surfactant enhanced air sparging remediation in low permeability soil.The effects of surfactants on solubilization and adsorption/desorption of organic contaminants in cohesive soil were systematically studied.On this basis,the interaction effects between surfactant and organic contaminants and the mechanism of surfactant-enhanced air sparging in cohesive soil were revealed.Then,the air flow characteristics and the distribution of organic contaminants in the process of traditional air sparging and surfactant-enhanced air sparging were studied by using the self-designed two-dimensional model box air sparging test device and sampling test system,and the remediation effect of organic contaminants was obtained.The remediation efficiency of low permeability organic contaminated soil was compared and analyzed.Finally,based on the above research results,the key control parameters of surfactant enhanced air sparging remediation technology,namely air sparging pressure and surfactant concentration,were evaluated and analyzed.The main research results are as follows:The addition of surfactants will promote the dissolution of organic contaminants.The adsorption of organic contaminants on cohesive soil is significant,and its adsorption characteristics can be characterized by Henry model.The partition coefficient of MTBE in cohesive soil is 0.217L/g.Under the action of low concentration surfactant,the cohesive soil still plays a very strong role in the adsorption of organic pollutants.When the concentration increased to 1300mg/L,the surfactant could promote the desorption of organic contaminants,and the maximum desorption rate was 80%.The existence of high concentration surfactant makes more organic contaminants adsorbed on the medium desorb from the soil and enter the solution again,and inhibits the adsorption of dissolved organic pollutants on the soil.With the increase of surfactant concentration,the air sparging flow rate increases,and the curve of air sparging pressure and air sparging flow rate is closer to linear.During the process of surfactant enhanced air sparging,with the increase of air sparging pressure,the law of air flow is the same as that of traditional air sparging:the level of air flow increases and expands from the center to both sides.However,with the increase of surfactant concentration,the expansion range of air flow with air sparging pressure is larger.Under the same surfactant concentration,the removal efficiency of organic pollutants increased with the increase of air sparging pressure.The removal efficiency of organic pollutants in high concentration surfactant air sparging is higher than that in low concentration surfactant air sparging and traditional air sparging,and can effectively alleviate the tailing phenomenon in the process of organic pollutants removal.Combined with the comprehensive analysis of air flow and removal rate of organic pollutants,the key control parameters of surfactant enhanced air sparging restoration technology in soil were obtained and the optimal parameters were designed:the air sparging pressure was determined as 80kPa and the surfactant concentration was determined as 1500mg/L.