Recent advances of kinetic model in the separation of essential oils by microwave-assisted hydrodistillation

Abstract

To better design and optimize the separation process of plant essential oils obtained by microwave-assisted hydrodistillation , it is necessary to fully understand the kinetic mechanism and appropriate mathematical representation of the separation process. In this paper, the kinetic models, including first-order kinetic models, second-order kinetic models, two-site kinetic models, power-law models, Peleg models, and Elovich model, for the separation of essential oils by microwave-assisted hydrodistillation are introduced, and try to explain the kinetic behavior of this method for the separation of essential oils through the assumptions, parameters and application examples of the kinetic model. Meanwhile, the most suitable kinetic models were screened according to the kinetic mechanism of essential oils obtained by this method, although these kinetic models all showed a high coefficient of determination, only first- and second-order kinetic models can reproduce the kinetic mechanism of this method under specific conditions. In addition, the effects of microwave irradiation power, liquid-solid ratio, moisture content, and particle size on the kinetic model parameters are discussed and analyzed, then the extraction rate constants, equilibrium yields, and coefficients of determination in the kinetic models all change with these factors. Therefore, it is necessary to explore new kinetic models to more comprehensively understand the kinetic mechanism of the separation of essential oils by this method, which has guiding significance for the optimal design of essential oil separation methods and the utilization of high-value processing. • The MHD method can be approximated as only two simultaneous mechanisms. • First- and second-order kinetic models can well fit the MHD under certain conditions. • Kinetic model parameters are affected by the essential oil separation conditions. • Essential oils isolated by the MHD method are mainly derived from broken plant cells. • Adverse results such as thermal decomposition affect the kinetic mechanism of MHD.