Experimental data and modeling the supercritical fluid extraction of marigold (Calendula officinalis) oleoresin

The fixed bed extraction of marigold (Calendula officinalis) oleoresin with liquid and supercritical carbon dioxide was investigated. The operating conditions studied were: pressures ranging from 12 to 20 MPa and temperatures from 293 to 313 K, indicating solvent densities ranging from 666 to 938 kg(CO2)/m(3), and solvent flow rate varying from 1.3 x 10(-5) to 5.0 x 10(-5) kg(CO2)/s. The results show an increase in the extraction rate, observed through the overall extraction curves (OEC), with increasing pressure. The experimental data were correlated using three models based on differential mass balance equations: (1) the Sovova model; (2) the logistic model presented by Martinez et al. and (3) the desorption model proposed by Tan and Lion; and two models based on heat transfer analogy: (4) the simple single plate model (SSP), presented by Gaspar et al. and (5) the diffusion model, proposed by Crank and presented by Reverchon. All models fitted well the experimental data and the lowest deviation between experimental and correlated data was obtained with the logistic model, for all the experimental conditions evaluated. (c) 2004 Elsevier B.V. All rights reserved.