A novel anionic-nonionic Gemini surfactant SANG 13 for high-efficiency flushing remediation of halogenated...

Surfactant-enhanced aquifer remediation (SEAR) has been widely recognized as an effective technique for removing dense nonaqueous phase liquids (DNAPLs). Common monomeric surfactants often suffer from limitations such as precipitation, high adsorption losses, insufficient solubilization and mobilization capacities under subsurface conditions, reducing flushing efficiency. Our group previously designed and synthesized a novel sugar-based anionic-nonionic Gemini surfactant named SANG 13. However, its effectiveness in flushing and removing halogenated hydrocarbon contaminants has not yet been systematically evaluated and quantified. In this study, a series of column flushing experiments were conducted to investigate the remediation performance of SANG 13 for representative DNAPLs, including tetrachloroethylene (PCE), monochlorobenzene (MCB), and carbon tetrachloride (CTC). The results demonstrated that SANG 13 achieved near-complete removal (>90%) of all three contaminants within 10 pore volumes (PVs), without inducing undesirable emulsification. The response surface methodology (RSM) revealed that surfactant concentration and flushing flow rate were the primary factors governing remediation performance. In addition, the removal efficiency of PCE reached 99%, 95%, and 86% in medium sand, fine sand, and silt, respectively. Correspondingly, adsorption losses of SANG 13 increased with decreasing grain size, with values of 4.5%, 8.5%, and 26.8% in the three media. Overall, these findings highlight the excellent flushing performance and favorable characteristics of SANG 13, indicating its promising potential for field-scale SEAR applications targeting DNAPL-contaminated aquifers.