Gabriele Di Giacomo

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.

Recovery of α-amylase extracted by reverse micelles

Abstract The use of reverse micellar systems for protein extraction has attracted considerable interest because of their capacity to solubilize specific proteins from dilute aqueous solutions such as fermentation and cell culture media. A forward and back extraction can be used for the recovery of proteins. The conditions for the extraction of α-amylase protein have been investigated, with special reference to the recovery of enzymic activity. Protein release depended on aqueous phase pH; the α-amylase protein increasing at lower pH values of the back extraction aqueous phase. The enzyme retained its biological activity fairly well inside reverse micelles.

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.

Extraction of α-amylase protein by reverse micelles: II. effect of pH and ionic strength

Abstract Liquid-liquid extraction by reverse micelles can be used for the separation and purification of proteins from fermentation media. It represents a new downstream process for the extraction of enzymic molecules without any modification to their conformation. The partitioning of α-amylase protein between an organic phase, containing a quaternary ammonium salt (TOMAC), and an aqueous phase depends on the parameters of both phases. The ionic strength of the aqueous phase is one of these parameters and it affects the yield of the extraction process. Experiments have been performed at different molar concentrations of NaCl and results have shown that the partition coefficient of the α-amylase decreases and the protein extraction profile shifts towards higher pH values as the ionic strength increases.

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.

Extraction of Protein α-amylase by reverse micelles

Abstract Reverse micelles can be used for the recovery and concentration of proteins by traditional liquid—liquid extraction techniques. The efficiency of protein extraction depends on some parameters such as pH value of the aqueous phase because the main factor governing the solubilization process is the electrostatic interaction between the protein and the charged surfactant headgroups. The extraction of enzymatic protein α-amylase has been carried out using an aqueous phase composed of a borate buffer 25 m m and an organic phase consisting of isooctan, octanol (1% v/v) and cationic surfactant TOMAC. The experiments have been performed at different pH values and surfactant concentrations. The results have shown that the enzyme extraction improved through the increase of the aqueous pH value and TOMAC concentration. The molar ratio water to surfactant (W 0 ) depended on the amount of protein transferred into the organic phase.

Vapor-liquid equilibrium calculation of the system water-hydrogen chloride

Abstract Brandani, S., Brandani, V. and Di Giacomo, G., 1994. Vapor-liquid equilibrium calculation of the system water-hydrogen chloride. Fluid Phase Equilibria, 92: 67-74. The vapor-liquid equilibrium of the system water-hydrogen chloride has been described. The activity coefficients in the liquid phase are evaluated by an extended Pitzer model, where the reference state for hydrogen chloride is defined according to Henrys law. The results have been compared with those obtained using a modified Engels and Bosen model.

Hydrothermal carbonization of Biomass: New experimental procedures for improving the industrial Processes

This study aims to introduce new experimental methods, not yet described in the literature, to be adopted in hydrothermal carbonization processes. Silver fir was selected as model biomass in batch experiments in the range 200-300°C, up to 120min of reaction time, and at a 7:1 water to solid ratio. Simple equations were proposed for modeling the evolution of the process variables during the reaction, particularly the electrical conductivity of the liquid phase, correctly described by a simple two-step first order mechanism, regardless of the reaction temperature. At 200°C, a perfect correspondence (R2=0.9992) exists between liquid phase electrical conductivity and solid phase carbon content. The authors propose to monitor the industrial process withdrawing from the reactor the liquid and sampling its conductivity. The benefits of a flash expansion step between the reactor and the hydrochar drying units were discussed, and experiments demonstrated the usefulness of this process innovation.