Determination of Solid Deformation Effect on the Effective Diffusivity During Extraction from Plants

• Published in: Separation science and technology Vol. 38; no. 15; pp. 3713 - 3729
• Main Authors: Seikova, Ilona, Simeonov, Evgeni
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 10.01.2003
• ISSN: 0149-6395; 1520-5754
• DOI: 10.1081/SS-120024225

A short-cut method was developed to account for the swelling effect on the effective diffusion coefficient during the course of a solid-liquid extraction. Exemplary, the kinetics of alkaloid recovery from the plant Atropa belladonne in batch stirred vessel was reported. Supporting experiments were performed to obtain the solid volume modification that is associated with the kinetics of solvent penetration. The volume of the solvent-impregnated solid was changed by a factor of 1.4 to 1.7 during extraction. The analytical solutions of the model for a diffusion controlled process were checked with the experimental kinetics to determine the effective diffusion coefficients. The values varied between 3.68 × 10 − 10 m 2 s − 1 and 4.79 × 10 − 10 m 2 s − 1 (when considering volume modification) and between 2.52 × 10 − 10 m 2 s − 1 and 3.45 × 10 − 10 m 2 s − 1 , under constant volume system hypothesis. To interpret the difference between the effective diffusivities, a correction term was derived accounting for the geometric factors variations. The swelling was found to be three dimensional and the correction term, giving the relative volume change to power values of 0.666, produced a good fit with the experimental data.