Effective Diffusivity and Mass Transfer Coefficient during the Extraction of Paclitaxel from Taxus chinensis Using Methanol

Solid-liquid extraction of paclitaxel from the biomass of Taxus chinensis was investigated in order to understand the effect of temperature, solvent concentration and stirring speed on the mechanism and kinetics of extraction. Paclitaxel concentration-time data were analyzed using a second-order kinetic model to determine the kinetic parameters. A diffusion model was utilized to determine diffusivity and mass transfer coefficient taking into account both washing and diffusion phases together. The effective diffusion coefficient (1.2814 × 10 −13 -5.9765 × 10 −13 m 2 /s), mass transfer coefficient (1.0020 × 10 −7 -1.2598 × 10 −7 m/s), and Biot number (3.927–8.959) increased with increasing temperature (298–318 K), methanol concentration (75–100%) and stirring speed (170–570 rpm), which indicated that the external resistance to mass transfer is negligible due to efficient mixing of solute and solvent.