Properties of Chitosan Microgranules Formed by Supercritical Fluid Processing

Abstract

Microgranules of chitosan were formed by a multistage process consisting of: (1) formation of chitosan hydrogel by the phase inversion method using chitosan salt solution and gaseous ammonia as a precipitant, (2) formation of alcogel by replacing the water-based residual solution left in the hydrogel structure by a less polar secondary solvent soluble in near-critical CO₂ such as acetone or methanol, (3) removal of this secondary solvent by supercritical CO₂ drying, and (4) disintegration of the solid but brittle structure. Key structural characteristics of microspheres such as pore volume and surface area were determined. Specific pore surface area of microspheres (<2 µm) ranged from 200 to 500 m²/g. Structural characteristics of microgranules were compared with those of microgranules formed by spray drying and granules of the chitosan hydrogel obtained by freeze drying.

Keywords:

• Chitosan
• Microgranules
• Porosity structure

ACKNOWLEDGMENTS

This research was financed by the Polish Science Fund under grant No. N 207 037 31 1459.

Notes

^a From Dubinin-Radushkevich (D-R).^{[ 42 ]}

^a Pores accessible for carbon dioxide molecules but inaccessible for benzene molecules

^b From Dubinin-Radushkevich (D-R).^{[ 42 ]}

^a From Dubinin-Radushkevich (D-R).^{[ 42 ]}

^a From Dubinin-Radushkevich (D-R).^{[ 42 ]}