Analysis of the removal process of residual tetrachloroethylene from simulated aquifer by a novel anionic-nonionic gemini surfactant.

With excellent solubilization capacity and aquifer suitability, GEO3S-12, a novel anionic-nonionic gemini surfactant, holds great promise in surfactant-enhanced aquifer remediation technology (SEAR) for tetrachloroethylene (PCE) removal from aquifers. However, PCE removal modes, environmental factors, and engineering control parameters affect the removal effect of residual PCE from aquifers. In this work, the main removal mode of residual PCE from the simulated aquifer by GEO3S-12 was characterized using the microscopic model and the macroscopic simulation column of laboratory-scale aquifer cell. The influences of environmental factors and engineering control parameters on residual PCE removal effect were investigated through one-dimensional simulation column. The solubilization remediation effect of the PCE-contaminated simulated aquifer by GEO3S-12 was evaluated in a two-dimensional simulation tank. The results indicated that the solubilization was the dominant mechanism of residual PCE removal by GEO3S-12 when the residual PCE was partially distributed in the aquifer. The environmental factors including particle size of the simulated aquifer, contact time between GEO3S-12 and PCE-NAPL, and saturation of residual PCE jointly control the removal effect of PCE. And a quadratic function model of environmental factors was constructed to predict the PCE removal effect. The optimal PCE solubilization removal effect could be achieved by using the GEO3S-12 injection concentration that was 40 g/L first and then 20 g/L, low injection velocity (1.9 m/d), and intermittent injection mode. The solubilization effect of GEO3S-12 increased the aqueous-phase PCE concentration at the lower right corner of the simulated aquifer that away from the source from 10 mg/L to 10,000 mg/L. The percentage of PCE removal amount from the simulated aquifer by GEO3S-12 was 97.11 %. The findings provide guidance for how to adjust engineering parameters of SEAR based on the aquifer environmental factors to achieve the best PCE-contaminated site remediation effect.