Influence of interfacial properties on yield and morphology of biomass microbeads produced by a scalable emulsion procedure

Plastic microbeads are widely used as exfoliants and rheological modifiers to improve viscosity, bulking, and film formation in personal care consumer products (PCCPs). While almost all of the beads are removed by sedimentation processes during wastewater treatment, billions of these microplastics enter the environment daily in the US alone. To produce biomass microbeads in a scalable process with comparable sizes and stiffnesses – around 1 GPa and several hundred microns – solutions of Kraft lignin and cellulose in ionic liquid are emulsified in oil, and precipitated by dripping in an anti-solvent, before being filtered, washed, and extracted to remove residual ionic liquid. While this method accesses the desired size range, the chaotic mechanism of precipitation results in bead surfaces that are inhomogeneous, which is not conducive to their target as gentle exfoliants. Furthermore, these inhomogeneities can cause clumping during the filtration, leading to a reduction in effective yield of individual beads. To modify bead morphology and yield, we studied the influence of interfacial properties, as mediated by incorporation of surfactants and choice of oil, allowing the rational design of a wide range of microbeads for various consumer applications. We aim to use this new technique to produce a scalable, sustainably sourced and degradable alternative to a major source of primary microplastics.