• • The 10× CMC rhamnolipid+alkyl polyglycoside (RL+APG) combined treatment (Exp IV) achieved the highest PAH removal of 106.02 mg·kg⁻¹, with average soil current intensity and moisture content 1.31 and 1.12 times that of the control (CK), respectively, demonstrating superior electrokinetic performance and PAH solubilization.
• • Biosurfactant addition significantly promoted bacterial proliferation: the 10× CMC RL+APG treatment increased bacterial counts by 6.24-fold in contaminated soil and 44.8% in the biobarrier layer, indicating enhanced microbial activity crucial for sustained biodegradation.
• • Optimal biosurfactant concentration is critical: 5× CMC RL+APG provided the best trade-off, maximizing PAH removal while preventing PAH accumulation in the biobarrier and clean soil, whereas higher concentrations (7.5× and 10× CMC) caused PAH breakthrough and secondary contamination risks.
• • Combined biosurfactants (RL+APG, RL+SAP) outperformed single surfactants in enhancing PAH removal and microbial growth, highlighting synergistic effects that improve micellar solubilization and bioavailability, which is essential for field-scale remediation of high-molecular-weight PAHs.