Investigation of mass transfer coefficients in the extraction of flavonoid content from chamomile effluent obtained by hydrodistillation in a RDC column

The essential oil and effluent of herbs contain various active components, of which flavonoids are a big family. The wastewater of chamomile obtained from hydrodistillation is used as a continuous phase in the rotating disk column. Also, n-hexane was chosen as the dispersed phase. This study investigates the extraction of flavonoids using liquid–liquid extraction and examines the theoretical and empirical relations for mass transfer coefficients and effective diffusivity in chamomile effluent. The operating parameters are the rotor speed, dispersed phase flow rate, and continuous phase height. The response surface method has been considered, and a new empirical model has been proposed to predict the extraction efficiency as a function of operating parameters applying an optimal design. The results showed that the extraction efficiency ranges from 25% to 50%. A simultaneous increase in operating parameters increases extraction efficiency, but the continuous phase height has an almost negligible effect. Moreover, the individual and overall volumetric mass transfer coefficients have been increased by increasing the rotor speed and dispersed phase flow rate. The comparison of the experimental mass transfer coefficient with Newman, Kronig-Brink, and Handlos-Baron's equations showed a good agreement of experimental data with the ones obtained from the Newman equation because of the rigid droplets.