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 CO 2 were studied in terms of temperature (40- 60 degrees C), pressure (18 - 30 MPa), specific CO 2 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 degrees C, 30 MPa, 30 kg CO 2 /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 19.26x10 - 12 m 2 /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).