Continuous production of cellulose microbeads via membrane emulsification

We report on the continuous manufacturing of cellulose microbeads as a sustainable alternative to plastic micro-particles, currently used in a wide range of consumer products, from toothpaste to paints. Plastic microbeads are not retained by, or degraded in, waste water treatment plants (due to their size and composition), accumulating in the environment in general and aquatic life in particular, eventually finding their way into the human food supply chain. Here it is demonstrated, for the first time, that a cross-flow membrane emulsification – phase inversion process can be used to generate stabilized micro-droplets of cellulose dissolved in an organic electrolyte solution (1-ethyl-3-methylimidazolium acetate:DMSO) in a sunflower oil-Span 80 continuous phase. The emulsion is subsequently coagulated with an anti-solvent, resulting in the formation of solid, spherical and biodegradable cellulose microbeads. A systematic analysis of process parameters (continuous and disperse phase flow rate, viscosity and applied pressure) allowed the determination of a regime within which microspheres can be predictably produced using a 10 µm pore size porous glass membrane. Cross-linking of the cellulose beads with glyoxal led to a 3-fold increase in compressive strength of the beads, broadening the potential range of applications where these biodegradable particles could replace current environmentally persistent materials.