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Water subcritical

Among the reactions studied in supercritical and subcritical water [77f, 78] the first report on a Diels-Alder reaction appeared in 1997 [79]. [Pg.285]

Some other Diels Alder reactions have been investigated in subcritical water [79] and some of them are illustrated in Scheme 6.33. The cycloadditions are fast and occur with good yields. In the absence of solvent, the reagents tend... [Pg.285]

CO2 extraction has been prevalent for the isolation of essential oils and other natural lipophilic pigments like carotenoids. Hot water and superheated water extraction methods are used for analytical preparation of polar pigments. The technique is commonly referred to as subcritical water extraction because the practitioners of this approach come from SEE backgrounds. [Pg.305]

There are two distinct conditions that have been used above the critical temperature and pressure (374°C and 218 atm) water becomes a supercritical fluid in which the distinction between the liquid and gaseous states disappears. Since supercritical water can dissolve nonpolar compounds, it has been examined for the degradation of such contaminants. Subcritical water in which the liquid state is maintained by the pressure of the containing vessel has also achieved attention. [Pg.36]

Destruction of the explosives RDX, HMX, and TNT has been examined using subcritical water in both laboratory- and pilot-scale experiments. In contaminated soils at 150°C, considerable amounts of TNT remained in the soil after reaction for 5 h, and of HMX for 2.5 h. In the pilot-scale experiments, heating at 275°C for 1 h accomplished complete destruction of RDX and TNT, and ca. 98% destruction of HMX (Hawthorne et al. 2000). [Pg.36]

The use of subcritical water at 275°C was successful in removing PAHs with two to six rings (including the carcinogenic benzo[a]pyrene) from soil at a contaminated site, and the wastewater that was produced appeared to be suitable for further exploitation (Lagadec et al. 2000). [Pg.37]

Hawthorne SB, AJM Lagadec, D Kalderis, AV Lilke, DJ Miller (2000) Pilot-scale destruction of TNT, RDX, and HMX on contaminated soils using subcritical water. Environ Sci Technol 34 3224-3228. [Pg.42]

Kubatova A, AJM Lagadec, SB Hawthorne (2002) Dechlorination of lindane, dieldrin, tetrachloroethane, trichloroethene and PVC in subcritical water. Environ Sci Technol 36 1337-1343. [Pg.43]

Lagadec AJM, DJ Miller, AV Lilke, SB Hawthorne (2000) Pilot-scale subcritical water remediation of polycyclic aromatic hydrocarbon- and pesticide-contaminated soil. Environ Sci Technol 34 1542-1548. [Pg.43]

Organic solvent-less techniques (e.g. subcritical water extraction, headspace SPME). [Pg.54]

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... [Pg.60]

Principles and Characteristics Water is an interesting alternative for an extraction fluid because of its unique properties and nontoxic characteristics. Two states of water have so far been used in the continuous extraction mode, namely subcritical (at 100 °C < T < 374 °C and sufficient pressure to maintain water in the liquid state) and supercritical (T>374°C, p>218 bar). Unfortunately, supercritical water is highly corrosive, and the high temperatures required may lead to thermal degradation of less stable organic compounds. However, water is also an excellent medium for extraction below its critical temperature [412], Subcritical water exhibits lower corrosive effects. [Pg.100]

Applications Subcritical water extractions with suitable adjustments to the temperature (up to 250 °C)... [Pg.100]

With suitable adjustments to the temperature, also subcritical water extraction (SWE) or pressurised hot water extraction (PHWE) allows selective extraction of polar (chlorinated phenols), low-polarity (PCBs and PAHs) and nonpolar (alkanes) organic compounds from industrial soils [418]. [Pg.140]

Boundaries in chromatography and extraction are blurring, as evident from the relation between GC, SFC and HPLC, the use of superheated/subcritical water for extraction and chromatography, and the role of enhanced fluidity solvents and pressurised fluid extractions [2]. Extraction is an extreme form of chromatography. Separation science recognises that there is unity in the... [Pg.172]

Although SFC fills a niche in what can be considered as a continuum of separation eluents from gases to liquids, it cannot claim a unique status subcritical water extraction (SWE, cf. Section 3.4.3) and pressurised fluid extraction (PFE, cf. Section 3.4.6) are other examples of eluents where altering the conditions cause a useful change in the solvation properties. [Pg.212]

Bruno F, Curini A, Di Corcia A, Fochi I, Nazzari M, Samperi R (2002) Determination of surfactants and some of their metabolites in untreated and anaerobically digested sewage sludge by subcritical water extraction followed by liquid chromatography-mass spectrometry. Environ Sci Technol 36 4156—4161... [Pg.106]

Numerous organic transformations have been carried out in subcritical water under conventional thermal conditions [35]. The application of microwave heating... [Pg.66]

Fluid Ordinary water Subcritical water Supercritical water... [Pg.66]

Yang et al. [56] used subcritical water to extract polychlorobiphenyls from soil and sediments. Quantitative recovery of polychlorobiphenyls was observed at water temperatures of 250 and 300°C when the pressure was reduced to 50atm at 300°C the extraction was complete within 5min. [Pg.174]

The procedure [56] involving subcritical water extraction of polychlorobiphenyls from soils described in section 5.6.1.4 has also been applied to sediments. [Pg.177]

A second SFE-based method for the extraction of NPEC from solid matrices is called subcritical (hot) water extraction [9], The method was applied for NPEi 4C in 0.25 g sludge samples. Subcritical water is used as the extraction solvent, with 30% ethanol as the modifier, yielding quantitative recoveries. Other tested extraction solvent compositions were C02, hot water, methanol-modified hot water, none of which were judged satisfactory. [Pg.451]


See other pages where Water subcritical is mentioned: [Pg.499]    [Pg.149]    [Pg.25]    [Pg.37]    [Pg.602]    [Pg.434]    [Pg.51]    [Pg.81]    [Pg.100]    [Pg.100]    [Pg.553]    [Pg.732]    [Pg.46]    [Pg.160]    [Pg.210]    [Pg.58]    [Pg.265]    [Pg.450]   
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