Effect of process parameters on the extraction kinetics of Leptocarpha rivularis DC. in a packed bed extractor using supercritical carbon dioxide

The kinetics of supercritical extraction from L. rivularis stalks using CO₂ were studied in terms of temperature (40−60ºC), pressure (18–30 MPa), specific CO₂ consumption (30−50 kg/kg d.s.), and particle diameter (0.5−1.1 mm). The extraction yield was found to range from 17.30 to 27.23 g/kg d.s. The highest extraction yield was obtained at 40°C, 30 MPa, 30 kg CO₂/kg d.s., and mean particle size of 0.5 mm. The yield increased with pressure and decreased with temperature and particle size (p≤0.05). The diffusion model based on Fick's 2nd law adequately described the cumulative extraction curves, using the effective diffusion coefficient (D_e) as the adjusted parameter, which ranged between 3.50 and 19.26×10⁻¹² m²/s. The Biot number was estimated, indicating a prevalence of internal control to mass transfer resistance. Additionally, the “apparent solubility” was obtained from the initial slope of the cumulative extraction curves. The extraction yield correlated positively with apparent solubility (p≤0.05) and D_e coefficient (p≤0.05).