Giovanni Del Re

Solubility of essential oil components in compressed supercritical carbon dioxide

Abstract The solubility of pure limonene and of citral in supercritical carbon dioxide was measured at temperatures ranging from 308.2 to 323.2 K and at pressures ranging from 3.0 to 11.0 MPa. The solubility and selectivity of different mixtures of limonene and citral were also measured in supercritical carbon dioxide at 323.2 K and at pressure from 9.49 to 10.0 MPa. The results show that compressed supercritical carbon dioxide extraction can be considered as an interesting alternative to other conventional processes for the separation of liquid mixtures of lemon oil components.

Binary and ternary phase behaviour of the system water-ethanol-carbon dioxide

Abstract A perturbed-dipolar-hard-spheres equation of state for multicomponent mixtures of polar compounds, which was applied to the correlation of thermodynamic properties of pure fluids and of several binary systems containing at least one polar component is applied here to the correlation of thermodynamic properties of the system ethanol-carbon dioxide up to the critical pressure and to prediction of phase behaviour of the ternary system water-ethanol-carbon dioxide over pressure, temperature and concentration ranges of potential industrial interest. New experimental data are given for the system water-ethanol-carbon dioxide. Our data are compared with data from literature, and with ethanol loading in supercritical carbon dioxide and solvent selectivity predicted by the model.

Removal and destruction of toxic micropolluting organic compounds from waste waters by a combined NF and SCWO process

Supercritical Water Oxidation (SCWO) has been proposed almost 20 years ago as a potential waste treatment process since it can be used to destroy any organic polluting material dissolved or suspended in aqueous solutions or sludge. In fact, since oxygen or air and supercritical water are completely miscible, and organic compounds are quite soluble in supercritical water, complete oxidation of such compounds can be achieved. As a result, all the polluting compounds are converted to harmless gaseous or liquid substances such as carbon dioxide and water. SCWO usually operates at a pressure of about 25 MPa and at a temperature between the critical temperature of water and 850°K. Pure oxygen, air or hydrogen peroxide can be used as oxidizing agents. In comparison with other waste purification processes, SCWO is characterized by high investment and operating costs, but application of SCWO may result in an ultimate solution of the waste disposal problem. This is very important when dealing with very dangerous polluting compounds which are usually present in waste waters as micropolluting substances. In this paper a new wastewater purification process for the removal and destruction of toxic substances is described and discussed. This process is based on the coupling of a nanofiltration (NF) section with a SCWO section in order to reduce both the investment and operating costs, while retaining final destruction of toxic substances and high level of purification.

Liquid-liquid equilibria of the ternary system water/2-butyloxyethanol/n-decane at three different temperatures

Abstract Brandani, S., Brandani, V., Del Re, G. and Di Giacomo, G., 1994. Liquid-liquid equilibria of the ternary system water/2-butyloxyethanol/n-decane at three different temperatures. Fluid Phase Equilibria, 94: 313-320. Two and three phase equilibrium data obtained from the ternary system water/2-butyl-oxyethanol/n-decane at 25, 30 and 35°C are presented in this paper together with the points of the binodal curves. The experimental tie-lines are correlated with the NRTL and UNIQUAC models using a computational algorithm developed by Brandani to obtain the model parameters and to perform phase equilibria calculations.

Liquid chromatographic method for the analysis of tocopherols in malt sprouts with supercritical fluid extraction

A simple, specific and sensitive high-performance liquid chromatographic method has been developed for the determination of tocopherols in malt sprouts. A supercritical fluid extraction (SFE) procedure was used to isolate tocopherols from the vegetal matrix before quantitative analysis. The analytes were separated on a Zorbax reversed-phase column using methanol-water as mobile phase and quantified by measuring its fluorescence at lambda(em)=328 nm after excitation of the analytes at lambda(exc)=303 nm. The limits of detection for alpha-, gamma- and delta-tocopherols were 0.04, 0.05, and 0.05 microg/ml, respectively. The calibration graphs of the method were linear from 0.1 to 1.5, 0.2 to 2.5, and 0.2 to 2.0 microg/ml, for alpha-, gamma- and delta-tocopherols, respectively. This SFE and HPLC procedure is simple, precise and accurate for the determination of tocopherols in malt sprouts.

Phase equilibria of essential oil components and supercritical carbon dioxide

Abstract The solubility of pure essential oil components and their binary mixtures in supercritical carbon dioxide was correlated using an equation of state with density-dependent mixing rules. This equation was then used to predict the phase diagram of the two binary carbon dioxide—limonene and carbon dioxide—citral systems at temperatures from 308.2 to 323.2 K and over the whole range of pressure and composition. In addition, the phase behaviour of ternary carbon dioxide—limonene—citral system was calculated at pressures from 9.0 to 10.9 MPa at 323.2 K and over the whole range of composition.

Thermodynamics of aqueous solutions of boric acid

Vapor pressures of aqueous solutions of boric acid over a wide range of acid concentrations were measured from 40 to 100°C. The results, together with solubility data taken from the literature, can be described with a thermodynamic model which uses the Wilson equations to express the activity coefficients of water and boric acid. Only three temperature independent adjustable parameters are required; one of these represents the entropy of fusion of boric acid, data which are not available in the literature.

Equation of state for mixtures containing polar compounds

Abstract The new equation of state proposed by Brandani has been extended to mixtures, and appropriate mixing rules have been used for the parameters. Three adjustable binary parameters have been used to fit the experimental data of 13 binary mixtures containing at least one polar compound, with the exception of the system carbon dioxide— n -butane. The results of the fitting are satisfactory. When applied to a ternary mixture, predicted and experimental compositions of the liquid and vapor phase agree very well.

Thermodynamic properties of polar fluids from a perturbed-dipolar-hard-sphere equation of state: mixtures

Abstract A new equation of state similar to that proposed by Bryan and Prausnitz is applied to correlation of thermodynamic properties of six pure fluids and five binary systems containing at least one polar component. By using only two adjustable parameters our equation gives satisfactory results. The reference system, as in the equation of Bryan and Prausnitz, has the same dependence on density as that given by Carnahan-Starling equation, but the coefficients are now functions of temperature through the reduced dipole moment. The difference between our equation and that of Bryan and Prausnitz is the different choice of the power of the reduced dipole moment, which facilitates the extension to mixtures of polar fluids. This is achieved by using the mixing rules of Winkelman for the reduced dipole moment and using the two fluid theory of Whiting and Prausnitz.

Thermodynamics of hydrothermal solutions: Calcium carbonate and calcium sulphate solubility in a four-phase system

Abstract A thermodynamic model for the system CaCO 3 -CaSO 4 ·2H 2 O-NaCl-CO 2 -H 2 O has been developed for calculating calcium carbonate solubilities as a function of the carbon dioxide pressure under vapour-liquid-solid equilibrium conditions. The model has been tested against available data and its predictive capability compares favourably with that of other proposed models. Numerical values for model parameters are also given. The main feature of the model used in the present work is that the excess Gibbs energy is the sum of three terms: a Debye-Huckel contribution, a Born term as a correction for the change in dielectric constant and a short range interactions contribution calculated according to the non-random two-liquid (NRTL) equation. Our results may be useful in describing and interpreting the general characteristics of hydrothermal solutions with a view to their utilization for energy production.