Enrique Martínez de la Ossa

Extraction of carotenoids and chlorophyll from microalgae with supercritical carbon dioxide and ethanol as cosolvent

The extraction of carotenoids and chlorophylls using carbon dioxide modified with ethanol as a cosolvent is an alternative to solvent extraction because it provides a high-speed extraction process. In the study described here, carotenoid and chlorophyll extraction with supercritical CO(2 )+ ethanol was explored using freeze-dried powders of three microalgae (Nannochloropsis gaditana, Synechococcus sp. and Dunaliella salina) as the raw materials. The operation conditions were as follows: pressures of 200, 300, 400 and 500 bar, temperatures of 40, 50 and 60 degrees C. Analysis of the extracts was performed by measuring the absorbance and by using empirical correlations. The results demonstrate that it is necessary to work at a temperature of 50-60 degrees C and a pressure range of 300-500 bar, depending on the type of microalgae, in order to obtain the highest yield of pigments. The best carotenoid/chlorophyll ratios were obtained by using supercritical fluid extraction + cosolvent instead of using conventional extraction. The higher selectivity of the former process should facilitate the separation and purification of the two extracted pigments.

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.

Green Extraction of Antioxidants from Different Varieties of Red Grape Pomace

The extraction yield, phenolic content, anthocyanin content and antioxidant activity of extracts from different varieties of red grapes, Cabernet Sauvignon, Merlot, Petit Verdot, Syrah, Tempranillo and Tintilla, using pressurized green solvents have been analyzed. Two techniques were studied and compared: supercritical fluid extraction (SFE) with CO2 + 20% ethanol and pressurized liquid extraction (PLE) with either ethanol, water or an ethanol/water mixture as the extraction solvents. The Petit Verdot variety allowed the highest global and phenolic yield, and antioxidant activity. The best conditios for PLE obtained from the experimental design and kinetic study were 50% ethanol/water as the pressurized solvent at 90 bar, 120 °C, a flow rate of 5 g/min and, an extraction time of 90 min. A statistical analysis of variance has been performed and it was found that temperature is the only variable that has a statistical influence on the extraction yield. The antioxidant activity levels of the extracts are very promising and they are similar to those obtained with the antioxidant tocopherol.

High Pressure Extraction of Antioxidants from Solanum stenotomun Peel

In the work described here, two techniques for the recovery of anthocyanins from potato peel were studied and compared. One of the techniques employed was supercritical fluid extraction (SFE) with pure CO2 or with CO2 and ethanol as cosolvent and the other technique was pressurized liquid extraction (PLE), where the solvent used was ethanol in water acidified to pH 2.6. The effects of pressure and temperature were studied and the anthocyanin contents obtained were statistically analyzed. In SFE the use of low pressure (100 bar) and high temperature (65 °C) was desirable for the anthocyanin extraction. With PLE the anthocyanin contents are increased considerably, and the best yields were obtained at 100 bar and 80 °C. This result is in correspondence with antioxidant activity index values (1.66) obtained in a DPPH antioxidant activity assay. In the extracts obtained with PLE the phenolic compounds were also determined, but the main compounds presented in the extract are anthocyanins.

Remediation of PAH spiked soils: concentrated H2O2 treatment/continuous hot water extraction-oxidation.

Artificially contaminated soil with four different polynuclear aromatic hydrocarbons (acenaphthene, phenathrene, anthracene and fluoranthene) has been separately treated by two different processes: (A) concentrated hydrogen peroxide at mild conditions of temperature (343-393 K) and pressure (0.5 MPa) and (B) hot water extraction at relatively high temperature (523-657 K) and pressure (10 MPa). Both methods achieve acceptable PAH removal percentages from soil. Acenaphthene (the most soluble PAH) is completely removed with treatment A regardless of the operating conditions used. Under optimum conditions, the rest of PAHs are also eliminated to a high extent with both technologies. Temperature and hydrogen peroxide amount seem to play a major role in process A. Similarly, temperature and water flowrate are the most influencing parameters in process B. In the latter case, a post-stage for the extracting water cleaning is required.

Isolation of Bioactive Compounds from Sunflower Leaves (Helianthus annuus L.) Extracted with Supercritical Carbon Dioxide

The work described herein is a continuation of our initial studies on the supercritical fluid extraction (SFE) with CO2 of bioactive substances from Helianthus annuus L. var. Arianna. The selected SFE extract showed high activity in the wheat coleoptile bioassay, in Petri dish phytotoxicity bioassays, and in the hydroponic culture of tomato seeds. Chromatographic fractionations of the extracts and a spectroscopic analysis of the isolated compounds showed 52 substances belonging to 10 different chemical classes, which were mainly sesquiterpene lactones, diterpenes, and flavonoids. Heliannuol M (31), helivypolides K and L (36, 37), and helieudesmanolide B (38) are described for the first time in the literature. Metabolites have been tested in the etiolated wheat coleoptile bioassay with good results in a noteworthy effect on germination. The most active compounds were also tested on tomato seeds, heliannuol A (30) and leptocarpin (45) being the most active, with values similar to those of the commercial herbicide.

Simulation of Supercritical Water Oxidation with Air at Pilot Plant Scale

Abstract Supercritical Water Oxidation (SCWO) processes have been studied by nu-merous researchers. The effectiveness of this approach to treat a wide variety ofwastes has been proved and the kinetics involved in some cases have been de-scribed. Phenol is commonly present in industrial wastewaters and it is extremelytoxic. Hence, phenol is a model pollutant that has been the subject of numer-ous studies by SCWO on a laboratory scale. In this work, a pilot-scale SCWOsystem has been used to compare experimental and predicted conversions in theSCWO of phenol, using the reaction kinetic equations obtained at the laboratoryscale. In this context, “PROSIM PLUS” software was employed to develop asimulator for the pilot plant facility, with the reaction kinetic parameters adjustedto represent the experimental data. In this study it was necessary to determinethe thermal losses between the experimental reactor and its surroundings. Thesethermal losses were obtained from tests with pure water and oxidant streams inthe absence of chemical reaction. An equation that predicted the effect of flowrate and temperature on the thermal losses was used. Experimental oxidation testswere conducted with initial temperature in the range 380 to 425Supercritical Water Oxidation (SCWO) processes have been studied by numerous researchers. The effectiveness of this approach to treat a wide variety of wastes has been proved and the kinetics involved in some cases have been described. Phenol is commonly present in industrial wastewaters and it is extremely toxic. Hence, phenol is a model pollutant that has been the subject of numerous studies by SCWO on a laboratory scale. In this work, a pilot-scale SCWO system has been used to compare experimental and predicted conversions in the SCWO of phenol, using the reaction kinetic equations obtained at the laboratory scale. In this context, “PROSIM PLUS” software was employed to develop a simulator for the pilot plant facility, with the reaction kinetic parameters adjusted to represent the experimental data. In this study it was necessary to determine the thermal losses between the experimental reactor and its surroundings. These thermal losses were obtained from tests with pure water and oxidant streams in the absence of chemical reaction. An equation that predicted the effect of flow rate and temperature on the thermal losses was used. Experimental oxidation tests were conducted with initial temperature in the range 380 to 425 C, at 250 bar and phenol concentrations ranging from 1 to 12 g/l. Good agreement in the simulation was obtained by adjusting the kinetic parameters within their confidence range. This simulator was used to optimize the SCWO of phenol solutions in the pilot plant facility.

SFE kinetics of bioactive compounds from Helianthus annuus L.

The kinetics of the supercritical fluid extraction of bioactive compounds from sunflower using CO(2) as solvent were studied in order to establish an efficient method for this extraction. The influence of time of extraction at different solvent flow rates was investigated. The extraction pressure and temperature were optimized in previous studies and these values used were 400 bar and 50 degrees C. The extraction yields and the bioactivity levels of the extracts were also analysed. The results indicate that the most appropriate extraction time is between 120 and 180 min depending on the solvent flow and the pretreatment of the sample. The dried sample extracted at 40 g/min, the congealed sample extracted at the same flow and 180 min, and the dried sample extracted at 25 g/min for 120 min showed the best activity profiles. The extractions were carried out in a pilot plant with an extraction vessel with a capacity of 2 L.

Supercritical Water Oxidation for Wastewater Destruction with Energy Recovery

Abstract Supercritical water oxidation (SCWO) is a promising technology that respecting the environment destroys wastes definitely and allows an energy recovery. This process has been applied to many model compounds and real wastewaters at laboratory scale. However SCWO treatments at pilot plant scale of real wastewaters are much more limited in literature. Furthermore, the application of this technology to industrial wastewaters has some drawbacks as corrosion, salt deposition, management of biphasic wastes, presence of suspended solids and high costs, so nowadays the industrial scale-up is scarce and it is being delayed. As an attempt to reduce process costs, energy recovery from the effluent of the reactor has been studied by several authors. In this chapter, the main aspects of the SCWO are briefly described and the studies regarding energy recovery are summarized.

Supercritical CO2 extraction of PAHs on spiked soil: co-solvent effect and solvent regeneration by ozonization.

The supercritical CO(2) extraction of four PAHs (acenaphthene, phenanthrene, anthracene and fluoranthene) from an artificially contaminated soil has been investigated. The effect of temperature (40-60 degrees C), pressure (300-500 bar) and extraction time (90-150 min) has been assessed by conducting a Box-Behnken experimental design. The results suggest the existence of perturbation variables other than the aforementioned controlled variables leading to a significant dispersion of extraction recoveries. With the exception of anthracene, an optimum in temperature (50 degrees C) is envisaged when extracting the PAHs. Analogously, with the exception of anthracene (positive effect), pressure does not have a significant influence. The recovery yield increases as extraction time is increased to a value of 120 min. No further improvement is experienced thereafter. If a co-solvent is used (H(2)O(2) aqueous solution) a beneficial effect can be noticed. Hydrogen peroxide concentration did exert no significant influence in the process. Methanol used to collect the extracted PAHs could be regenerated by gaseous ozone and reused in several consecutive runs.