Research On Perchloroethylene Contaminated Soil Remediation Using Mixed Surfactant

Contamination of soil and groundwater by non-aqueous phase liquids (NAPLs) is a major environmental problem. Surfactant enhanced remediation (SER) are usually used to control this kind of pollution by individual anionic or nonionic surfactant. In this paper, perchloroethylene (PCE) remediation had been examined using single and mixed surfactant, SDS and Tween 80, with static and dynamic experiments. The experimental results demonstrated that the critical micelle concentration (CMC) value of mixed surfactant declined as more Tween 80 was added. PCE solubility in solution was enhanced by both of individual and mixed surfactant above CMC. The equilibrium solubility of PCE had good linear relationship with initial surfactant concentration. Weight solubilization ratio (WSR) of surfactant followed the order of Tween 80＞SDS＞3:1＞1:1＞1:3 (SDS:Tween 80). However, molar solubilization ratio (MSR) values of PCE increased with Tween 80 mole fraction increasing in mixed surfactant and the solubilization capacity of single Tween 80 for PCE was strongest. It had been shown that there was no synergism solubilization for PCE in mixed system. Both of NaCl and CaCl2 could improve PCE solubility in surfactant solutions and the effect of CaCl2 was bigger. The adsorption capacity of single Tween 80 on soil was stronger than that on sand and both of the sorption isotherms corresponded with Langmuir isotherm. The equilibrium adsorbance on sand and soil were 1.70 mg/g and 11.48 mg/g, respectively. The sorption of Tween 80 could be reduced in the presence of SDS and the higher the SDS concentration, the more conspicuous the inhibition effect. In column flushing experiments, PCE removal was significantly improved by surfactant solution compared with distilled water. The impact order for PCE removal was surfactant concentration> inorganic salt concentration＞surfactant mass ratio＞flow rate.3SDS:1Tween 80 had the best removal result, followed by 1SDS:1Tween 80, and Tween 80 was the worst. PCE flushing efficiency would be high when surfactant concentration and inorganic salt were high and flow rate was small. Thus, it can be seen that mixed surfactant may have better repair effectiveness than single surfactant for non-aqueous phase liquids recovery, mixed surfactant application can be taken more into consideration in underground remediation.