Nonaqueous phase liquids volatilization

The majority of trichloroethylene present on soil surfaces will volatilize to the atmosphere or leach into the subsurface. Once trichloroethylene leaches into the soil, it appears not to become chemically transformed or undergo covalent bonding with soil components. When trichloroethylene was absorbed onto kaolinite and bentonite, the nuclear magnetic resonance (NMR) spectra showed no evidence of chemical reactions (Jurkiewicz and Maciel 1995). Because trichloroethylene is a dense nonaqueous phase liquid, it can move through the imsaturated zone into the saturated zone where it can displace soil pore water (Wershaw et al. 1994). 

The contaminant s aqueous solubility and density greatly influence its final disposition in water-solid systems. Dense nonaqueous phase liquids (DNAPLs) are chemicals with densities greater than water and typically low aqueous solubilities. DNAPLs naturally partition away from the aqueous phase and towards the solid phase, often pooling on top of an impermeable solid layer. On the other hand, light nonaqueous phase liquids (LNAPLs) possess densities less than water and have a tendency to pool on the water s surface where they may be prone to volatilization and photolysis reactions. Various liquid-solid partition coefficients have been... 

Separation of VOC fi om surfactant solution Hydrophobic membrane This process can be used to remove volatile nonaqueous phase liquids from surfactant-based soil washing and soil flushing solutions for recovery of the volatile compounds and reuse of the surfactant [108]... 

The thin film model thus far has been applied to the volatilization of chemicals dissolved in water. Chemical volatilization can also occur from a layer of nonaqueous phase liquid (NAPE) floating on a water surface (or spilled on the ground). NAPE refers to a liquid, such as a solvent or a liquid fuel, that does not readily dissolve in water and hence tends to remain as a separate liquid phase. There are two kinds of NAPE light NAPL... 

Many contaminants exist as immiscible nonaqueous phase liquids (NAPLs) in soil. These liquids do not fully solubilize in water and exist as a separate phase due to physical and chemical differences from water. NAPLs can be classified as light (less dense than water) nonaqueous phase liquids (LNAPLs) and dense (more dense than water) nonaqueous phase liquids (DNAPLs). A list of typical NAPLs and their important properties is presented in Table 8.8. As described elsewhere in this book (Chapter 15), NAPLs may solubilize, volatilize, and otherwise partition among phases. This section focuses on the advective transport of pure-phase NAPL. 

Heron, G. and Christensen, T. H, 1998, Thermally Enhanced Remediation at DNAPL Sites The Competition between Downward Mobilization and Upward Volatilization In Nonaque-ous-Phase Liquids — Remediation of Chlorinated and Recalcitrant Compounds (edited by G. B. Wickramanayake and R. E. Hinchee), Battelle Press, Columbus, OH, pp. 193-198. 

For simple HT/HP exposure tests involving either aqueous or nonaqueous phases with a gas cap over the solution, the total pressure is usually determined by the sum of the partial pressures of the constituents of the test environment, which will vary with temperature. Where liquid constituents are being used for the test environment, the partial pressure is usually taken to be the vapor pressure of the liquid at the intended test temperature (see Table 2 for steam pressure versus temperature). Vapor pressures for several other volatile compounds used in HT/HP corrosion testing can usually... 

Alternatives to aqueous processing or dry or nonaqueous processing techniques have heen tried hut none, until recently, have been used on a true industrial scale for fuel reprocessing. Examples of these include separations based on (1) differences in volatility of the hahdes, especially fluorine compounds (2) molten salt (liquid-liquid) extraction where fuel dissolved in a molten salt is then contacted with a heat resistant low volatility second phase such as 100% TBP or a liquid metal and, (3) electrorefining, where controlling the cell potential results in removal of a metal from a molten salt by the selective deposition (reduction) on a cathode. 

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