Assessment of a novel alcohol-in-biopolymer emulsion for enhanced remediation of diesel-contaminated soils

• Novel biopolymer-based emulsion enhances LNAPL removal from contaminated soils. • 1-pentanol induces diesel oil swelling, improving its mobilization in porous media. • Shear-thinning emulsion ensures stable and uniform displacement in porous media. • Porous media studies confirm complete diesel removal with minimal fluid injection. • Promising approach for sustainable soil cleanup, minimizing environmental impact. Conventional pump-and-treat technologies have demonstrated limited effectiveness in remediating soils contaminated with light non-aqueous phase liquids (LNAPLs), such as petroleum hydrocarbons. Non-conventional in-situ flushing with shear-thinning fluids, such as polymers, offers a promising alternative. However, even with polymer flushing, residual LNAPL ganglia may remain trapped in porous media, requiring further improvement of the flushing fluid to enhance remediation efficiency. In this study, we present a novel alcohol-in-biopolymer emulsion developed to enhance the recovery of residual diesel oil from porous media. Batch experiments were conducted to evaluate the partitioning behavior of fifteen different alcohols between the aqueous and diesel phases. The results revealed that 1-pentanol preferentially partitions into the diesel phase rather than the aqueous phase, leading to an increase in diesel oil volume via a swelling mechanism. Furthermore, 1-pentanol forms a stable and homogeneous emulsion when combined with an aqueous solution of the biopolymer xanthan gum, and the surfactant sodium dodecyl sulfate. The emulsion demonstrated high stability for over 30 days, ensuring its suitability for prolonged remediation processes. Rheological experiments confirmed the emulsion's shear-thinning behavior, which ensures stable and uniform displacement within porous media. A two-dimensional cell packed with silica sand was used to evaluate the efficiency of the emulsion in removing residual diesel oil. The results demonstrated that the emulsion propagates uniformly throughout the porous media, effectively achieving complete removal of residual diesel within 1.15 pore volumes of injection. Pore-scale visualizations revealed the swelling and subsequent mobilization of entrapped diesel ganglia induced by the emulsion, further confirming its efficacy. These findings highlight the potential of this novel alcohol-in-biopolymer emulsion to significantly improve diesel oil recovery from contaminated soils. Sketch illustrating LNAPL displacement by emulsion at pore-scale