Kostis Magoulas

Supercritical fluid extraction of celery seed oil

The supercritical fluid extraction of oil from milled celery seeds, using CO2 as a solvent, is presented in this study. The effect of the process parameters — pressure and temperature of extraction, particle size of celery seeds and flow rate of CO2 — on the extraction rate was examined in a series of experiments. The results indicated a significant increase in extraction rate with increase of pressure or decrease of the particle size of celery seed. A similar effect was observed with the increase of the solvent flow rate and decrease of temperature. The experimental data were described by an empirical model and two mass balance models: (1) a simplified model, which takes into account only the time dependence of the extract concentration in the two phases and is coupled with various equilibrium relationships, and (2) an extended Lacks model. The correlation results were satisfactory especially for the mass balance models, which account for the double regime — solubility and diffusion controlled regimes — of the extraction.

Prediction of the bioaccumulation of persistent organic pollutants in aquatic food webs.

Predictive correlations of the bioaccumulation factor of persistent organic pollutants in aquatic biota are presented as functions of their octanol/water partition coefficient. The correlations demonstrate the importance of differentiating among the different levels in the food web and of accounting for the pollutants bioavailability by considering the amount freely dissolved in water instead of the total concentration. They also reveal the significance of the pollutants octanol/water partition coefficient value on its biomagnification along the levels of the trophic chain. Prediction results, finally, demonstrate that the correlations provide reasonably accurate estimates of bioaccumulation, typically within an order-of-magnitude.

The selective dissolution/precipitation technique for polymer recycling: a pilot unit application

In this study, the selective dissolution/precipitation method for polymer mixture separation and recycling is evaluated. The method was successfully applied in a pilot unit designed and developed for the separation of polymer mixtures. Recycled polymers of comparable quality with that of the pre-used ones were recovered. Furthermore, the feasibility study for high-capacity units indicated the applicability of this technique from the economic point of view.

Prediction of solid–gas equilibria with the Peng–Robinson equation of state

Abstract In many applications related to Supercritical-Fluid (SCF) technology, solids are dissolved in SC fluids. Experimental data are now available for many systems but cannot cover all cases of potential practical interest. The prediction of solid solubilities in SC fluids, often in the presence of co-solvents, is useful for rational design of SCF extraction and related processes. Recently, thermodynamics has made considerable steps towards describing complex systems (gases with polar compounds) at high pressures using the so-called Equation of State/Excess Gibbs Free Energy (EoS/G E ) models. The success of these models is so far restricted to Vapor–Liquid Equilibria (VLE) for which they have been primarily developed and tested. In this work we evaluate such a predictive model, the LCVM EoS, for solid–gas equilibria (SGE) including systems with co-solvents. LCVM is chosen due to its success for VLE of asymmetric systems such as CO 2 with heavy alkanes and alcohols. Successful predictions are obtained for several solids as well as for some systems with co-solvents, but the results are less satisfactory for complex, multifunctional solids. A discussion of several factors, which affect modeling of SGE with cubic EoS, is included.

Prediction of the solubility of aromatic hydrocarbons in supercritical CO2 with EoSGE models

Abstract Prediction of the solubility of liquid and solid aromatic hydrocarbons in supercritical CO 2 with the recently proposed LCVM model and the MHV2 model is presented. Satisfactory results are obtained in the case of LCVM, considering in particular the uncertainty of experimental measurements at such low mole fraction values and the pure component properties involved. Correlation of existing data is also considered in order to determine the limits of our expectations for the prediction results, including cases where the required solid vapor pressures are not available.

Determination of partial molar volumes at infinite dilution of alcohols and terpenes in supercritical carbon dioxide

Abstract The use of supercritical fluid chromatography for determining partial molar volumes of alcohols and terpenes at infinite dilution in supercritical CO2 is presented and discussed. Partial molar volumes at infinite dilution are obtained from the variation of the retention properties with the density of mobile phase at 313.15 K and in the pressure range from 85 to 280 bar.

APPLICATION OF SUPERCRITICAL FLUID EXTRACTION IN INDUSTRIAL WASTE TREATMENT : THERMODYNAMIC MODELING AND DESIGN

ABSTRACT The use of supercritical fluid extraction (SFE) as a separation process for the treatment of industrial wastewater is examined. The performance of the LCVM EoS/GE model in thermodynamic modeling of the systems CO2/H2O/organic pollutant (aromatics, phenol, cresol), including the presence of a cosolvent, is evaluated. The design of a unit that processes the water/phenol system with carbon dioxide, with and without a cosolvent, is also examined. The use of a cosolvent is a very important parameter for the SFE process since it can cause a significant decrease in the total cost of the unit. Application of the process appears limited due to the lack of predictive models and the high cost of equipment.

Correlation and prediction of infinite-dilution partial molar volumes of organic solutes in SC CO2 using the Peng-Robinson and PHCT equations of state and the LCVM EOS/GE model

An extensive infinite-dilution partial molar volume (PMV) data base of various liquid and solid solutes in supercritical carbon dioxide, including the very recent experimental partial molar volume data reported by Spicka et al. [B. Spicka, A. Cortesi, M. Fermeglia, I. Kikic, Determination of partial molar volumes at infinite dilution using SFC technique, J. Supercrit Fluids 7 (1994) 171] and Cortesi et al. [A. Cortesi, I. Kikic, B. Spicka, K. Magoulas, D. Tassios, Determination of partial molar volumes at infinite dilution of alcohols and terpenes in supercritical carbon dioxide, J. Supercrit. Fluids 9 (1996) 141] is used for a comprehensive study of the capabilities of three different thermodynamic models for the prediction of infinite-dilution partial molar volume data. The models are two equations of state, i.e. the well-known Peng-Robinson cubic EoS and the perturbed hard-chain theory (PHCT) EoS, and an EoS/GE model, the recently proposed LCVM group-contribution model. Correlation of the whole data base has been also considered with the Peng-Robinson EoS in order to determine the capability of a cubic equation of state to describe PMV data. Generally, all models were found to be semi-quantitative in the PMV prediction, especially in the range of the PMV minimum. Satisfactory prediction results are obtained using the Peng-Robinson EoS with interaction parameters from phase equilibrium data, and the fully predictive LCVM model. Both LCVM and the PHCT models tend to overpredict the PMV of n-alkanes in carbon dioxide in the high-pressure region, while PHCT always gives less satisfactory prediction results.

Comparison of the performance of the LCVM model (an EoS/GE model) and the PHCT EoS (the Perturbed Hard Chain Theory Equation of State) in the prediction of the Vapor–Liquid Equilibria of binary systems containing light gases

Abstract The purpose of this work is to compare two models, which are able to perform Vapor–Liquid Equilibrium (VLE) predictions. The first one, the LCVM model, is an EoS/G E one and it has been successfully applied in the prediction of the VLE behavior of polar and non-polar systems, as well as, systems of dissimilar component size, such as those containing gases with large n -alkanes. The second one is PHCT, an equation of state based on the perturbed hard chain theory. It has also been successfully applied in binary systems of supercritical fluids and non-polar molecules and in systems containing light gases and large n -paraffins. The comparisons results presented in this paper, proved that the two models are comparable, concerning the ability to predict the VLE, as well as, the volumetric behavior of systems with low to medium component size difference (supercritical fluids with non-polar components up to about 10 carbon atoms). However, as the size difference increases, LCVM performs better, especially in the near critical region of such systems.

Recovery of fructose laurate produced through enzymatic esterification

Abstract A process for the recovery of fructose monolaurate, produced through enzymatic esterification, is presented. The key separation is the one between fructose monolaurate and the unreacted lauric acid, which is accomplished through liquid–liquid extraction (LLE) using mixtures of alcohol (methanol or ethanol), hexane and water. Calculations of a LLE column, which are based on experimental liquid–liquid equilibrium data measured in this work, suggest the feasibility of the proposed process.