Stability and flow behavior of polymer-enhanced foams for improved in-situ remediation of hydrocarbons: Effect of polymer-surfactant interactions.

Conventional in-situ hydrocarbon remediation technologies face challenges associated with high costs and low long-term efficacy. Aqueous foam injection presents a promising approach by enhancing volumetric sweeping efficiency. This study investigates the efficiency of polymer-enhanced foams (PEFs) for in-situ remediation of hydrocarbon-contaminated soil, focusing on the impact of Xanthan Gum (XG) biopolymer on foam stability against antifoaming diesel and the flow behavior in soil matrices. We examined two PEFs: Sodium Dodecyl Sulfate (SDS)-based and a blend of SDS and Cocamidopropyl Hydroxysultane (SDS-CAHS: SC)-based. Bulk foam tests pre-evaluated foam stability, while 1D sandpack experiments assessed PEFs' performance in porous media mimicking contaminated soil remediation. Stability tests showed that XG strengthens the foam by increasing liquid phase viscosity and improving overall foam stability. The findings emphasize the importance of the interactions inside polymer-surfactant complexes, where SDS was more impacted by XG than SC due to repulsive forces and hydrophobic interactions. Foam flow experiments revealed PEFs' higher mobility reduction factors (MRF) and noticable recovery improvement of the free-phase product (≥95 %) compared to traditional surfactant-based foams. This research provides valuable insights into optimizing PEF compositions, potentially guiding future scale-up applications for hydrocarbon-contaminated sites.