Production of alginate-based aerogel particles using supercritical drying: Experiment, comprehensive mathematical model, and optimization

Abstract

Alginate-based aerogel particles were produced by dripping alginate solution (2%, w/w) into CaCl2 solution (100 mM) followed by solvent exchange and supercritical drying (SCD). Hydrogel particles were first produced by the dripping method. Beads were separated from the CaCl2 cross-linking solution by filtration. Then, the solvent exchange was performed at room temperature by the immersion of the particles into ethanol/water mixtures. Next, the obtained alcogels were submitted to a SCD process at 12 MPa, 40 °C, and CO2 flow rate from 0.27 to 0.84 kg/h, and the recovered ethanol was gravimetrically measured. Finally, a comprehensive mathematical model was employed to describe the SCD process using the law of conservation of mass. The model, which resulted in two partial differential equations for the fluid and solid phases, was numerically solved using the finite difference method, successfully validated by the experimental data and employed in the sensitivity analysis and optimization.