Wet and dry highly porous cellulose beads from cellulose–NaOH–water solutions: influence of the preparation conditions on beads shape and encapsulation of inorganic particles

Abstract

Wet (swollen-in-water) and dry highly porous cellulose beads were prepared from cellulose–8%NaOH–water solutions by making droplets and coagulating cellulose in water bath. The shape of the beads varied from very flat plates to spheres. The influence of the preparation conditions (cellulose concentration, delay time, bath temperature, and the distance between the pipette and the bath surface) on the shape of the beads is discussed. Higher is the solution viscosity and weaker is the shock of the falling droplet on the bath surface, more spherical are the beads. Gelation of cellulose–NaOH solutions is shown to be a very important factor controlling bead shape. A simple way of encapsulation of various powders in cellulose beads is demonstrated and wet cellulose–inorganic composites were prepared. Highly porous (Aerocellulose) beads carrying encapsulated particles were made by drying coagulated cellulose under CO₂ in supercritical conditions.