Surfactants are a class of amphiphilic compounds which are essential in various industrial applications, as they can aid in the formation of emulsions, dispersion or act as wetting agents.(1) Despite their wide use, only less than 5% of the current surfactant market share consists of compounds entirely derived from plant wastes and renewable carbon. Lignin, which has an amphiphilic structure by nature, is an ideal candidate for the development of fully bio-based surfactants. However, the imbalanced ratio between hydrophilic and hydrophobic moieties, as well as a limited solubility in aqueous media, make this biopolymer still a challenging substrate to be used in real-world applications.(2)
In this work, we explored how the alkali-O2 oxidation (LigniOx technology) of several hardwood lignin streams, can alter the chemical structure of lignin by partly opening and converting phenolic aromatic rings into carboxylates, hence modifying and controlling the hydrophilic/hydrophobic ratio to an preferred value.(3) This fast and robust oxidation process, followed by recovery of lignin via membrane separation, as well as the thorough chemical and physical characterization of the starting and final materials, allows for a practical and easily scalable method to obtain a water-soluble and ready-to-use novel class of lignin-based surfactants. This work paves the way for a quick and scalable introduction of entirely biomass-based surfactants in the market.