SUPERCRITICAL FLUID EXTRACTION OF CAROTENOID FROM MICROALGAE WITH PROJECTED THERMODYNAMIC MODELS

In this study, two thermodynamic models (regular solution theory and equation of state) were applied to obtain carotenoid solubility in the supercritical carbon dioxide solvent. Theoretical data obtained from the models were compared with the experimental data extracted from a published paper. The use of equation of state as an empirical correlation for collating and predicting liquidliquid and liquid-dense tluid equilibrium is discussed. It is concluded that the estimation of some parameters required for these calculations would be difficult if the solute (carotenoid) was a complex substance in which little information was known, apart from its structural formula. An alternative procedure is to apply activity coefficient expression of the regular solution equations for each phase. Calculations along these lines are described and the physical basis for applying these methods under the relevant conditions was also presented. The regular solution theory approach in particular has been found to be encouraging for the mutual miscibility calculations for heavy components (such as carotenoid) particularly substances that are sensitive to temperature, though the interaction parameters for the prediction activity coefficients must be regarded as pressure dependent.