Capillary flooding of wood with microemulsions from Winsor I systems.

A new approach based on microemulsions formulated with at least 85% water and minority components consisting of oil (limonene) and surfactant (anionic and nonionic) is demonstrated for the first time to be effective for flooding wood's complex capillary structure. The formulation of the microemulsion was based on phase behavior scans of Surfactant-Oil-Water systems (SOWs) and the construction of pseudo-ternary diagrams to localize thermodynamically stable one-phase emulsion systems with different composition, salinity and water-to-oil ratios. Wicking and fluid penetration isotherms followed different kinetic regimes and indicated enhanced performance relative to that of the base fluids (water, oil or surfactant solutions). The key properties of microemulsions to effectively penetrate the solid structure are discussed; microemulsion formulation and resultant viscosity are found to have a determining effect in the extent of fluid uptake. The solubilization of cell wall components is observed after microemulsion impregnation. Thus, the microemulsion can be tuned not only to effectively penetrate the void spaces but also to solubilize hydrophobic and hydrophilic components. The concept proposed in this research is expected to open opportunities in fluid sorption in fiber systems for biomass pretreatment, and delivery of hydrophilic or lipophilic moieties in porous, lignocellulosics.