Investigated models for prediction of extraction of essential oils by subcritical water

Mechanisms and rate of mass transfer in SWE of essential oil was studied. The extraction curves at different temperatures, particle sizes and solvent flow rates are used to determine whether the extractions were limited primarily by the near equilibrium partitioning of the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of analyte desorption from the matrix (i.e. kinetics). Simple models have been applied to describe the extraction profiles obtained with subcritical water: a model based solely on the thermodynamic distribution coefficient KD, which assumes that analyte desorption from the matrix is rapid compared to elution; simple diffusion model; one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate from the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs during elution; two-site kinetic model; external mass transfer resistance model; Two-phase model and computational fluid dynamics (CFD) model.The results have been tried to compare with experimental data of previous works about SWE of Zataria multiflora Boiss.

Keywords:

subcritical water extraction , mechanism , modeling , essential oils