Micronization of chitosan via rapid expansion of supercritical solution

• Rapid expansion of supercritical solution was used to micronize chitosan.
• Response surface method was applied to optimize effective operating conditions.
• Increasing temperature and pressure leads to smaller chitosan particle diameters.
• Smaller effective nozzle diameter decreases the chitosan particle diameter.

In this study, rapid expansion of supercritical solution (RESS) was used to micronize the chitosan particles. Design of experiment was implemented with response surface methodology (RSM) using Mini Tab software 17. The operating temperature (30–70 °C), pressure (7–22 MPa) and effective nozzle diameter (500–1200 μm) were considered as the range of operating variables while spraying distance (1 cm) and nozzle length (5 mm) were held constant. The characterization (size and morphology) of the precipitated particles of chitosan was determined by scanning electron microscopy (SEM). The results show great reduction in the size of the precipitated particles of chitosan compared with the original particles. A decrease in the particle size of chitosan was found with increasing extraction pressure and temperature along with a decreasing of nozzle diameter. Response surface analysis verified that R2 and modified R2 of the model for 500 μm effective nozzle diameter were 97.19% and 95.18%, respectively.

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