Cork barriers combined with surfactant-assisted electrokinetics for remediation of diesel-contaminated soils

New approaches are needed to address soil contamination by total petroleum hydrocarbons (TPHs), which poses persistent environmental risks. This study investigated the integration of electrokinetic (EK) remediation with cork-based permeable reactive barriers (PRBs) assisted by surfactants as a strategy for treating diesel-contaminated soils. The effects of surfactant type, soil texture (sand and sandy loam), and electric field strength (1.0 and 1.8 V cm^-1) on diesel mobilization and retention in cork barriers were evaluated. Two surfactants with distinct ionic properties, sodium dodecyl sulfate (SDS, anionic) and Triton X-100 (non-ionic), were selected as representative models. The regranulated cork can sorb TPHs, with predicted maximum sorption capacities of (12 ± 4)×10^-6 and (8 ± 0.5)×10^-6 mol g^-1 for SDS and Triton systems, respectively. Electrokinetic trials revealed that sand-based systems exhibited negligible retention of TPHs (<1%) due to short residence times and low cation exchange capacity. While sandy loam systems achieved up to 22% retention in the cork barrier in Triton-assisted setups, which exhibited substantially higher transport and PRB retention efficiency of TPHs than SDS, likely due to better electroosmotic compatibility and neutral micelle behaviour that favour retention in the hydrophobic cork matrix. In the SDS systems, the reduced contaminant transport observed may have limited the PRB interception. The effect of the electric field strength (1.0-1.8 V cm^-1) was not significant. These findings highlight cork's potential as a natural, renewable, sustainable and low-cost medium for cork-based PRBs. The study provides useful insights into combining cork-based PRBs with EK remediation surfactant-assisted, which is a promising approach for capturing hydrophobic pollutants in situ.