Single sphere model fitting of supercritical carbon dioxide extraction from Quercus infectoria galls

Abstract

Q. infectoria galls, locally knowns as ‘manjakani’ in Malaysia and Indonesia, is a traditional medicine commonly used for postpartum recovery due to its strong astringency. The astringent properties of Q. infectoria galls is due to the high amount of tannin available in the extract. In this study, supercritical carbon dioxide (SC-CO₂) with the presence of absolute methanol (1:3 w/v) was used for the extraction of Q. infectoria galls. The SC-CO₂ extraction of the galls involve the diffusion and mass transfer process, represented by the value of diffusion coefficient (D_e) and the external mass transfer coefficient (k_f). Single sphere model (SSM) was adapted and fitted into the experimental data, and D_e was found to be in the range of 0.91 ×10^-11 to 9.99 × 10^-11 m²/s. The linear driving force approximation was used to determine the k_f values, which calculated to be in the range of 4.60 ×10^-6 m/s to 9.50 ×10^-6 m/s. SSM also pointed out that the SC-CO₂ extraction of Q. infectoria galls is governed by internal diffusion with Biot number (Bi) greater than 10.