Enhanced volatilization

Remediation activities at American Thermostat included the excavation and thermal treatment of over 13,000 cubic yards of soil and sediments contaminated primarily with perchloroethylene, trichloroethylene, and solvents. The soil was excavated and treated using a thermal treatment unit called the low-temperature enhanced volatilization facility (LTEVF). The performance test for the site s thermal unit had just been completed at the time of the inspection, so there was limited activity. 

The reverse reaction to give the gaseous species AlX(g) at high temperature accounts for the enhanced volatility of AIF3 when heated in the presence of A1 metal, and the ready volatilization of A1 metal in the presence of AICI3. Using calculations of the type outlined on p. 82 the standard heats of formation of the crystalline monohalides AIX and their heats of disproportionation have been estimated as ... 

Intercalation via complexation in the vapor phase (S2i). Thus, for example, the nonvolatile C0CI2 can be intercalated in the presence of AICI3 at 500°C, because of the enhanced volatility of the former. Graphite-C0CI2 containing only traces of AICI3 is obtained. 

The enhanced volatilization process is operated by putting contaminated soil in contact with clean air in order to transfer the contaminants from the soil into an air stream. The air stream is further treated through the use of carbon canisters, water scrubbers or afterburners to reduce air emission impacts. Four methods are available that can achieve this effect19 ... 

Of the four enhanced volatilization methods described above, documentation exists to support the contention that the low-temperature thermal stripping system has the greatest ability to successfully remove contaminants that are similar to gasoline constituents (i.e., compounds with high vapor pressures) from soil. The limitations of some enhanced volatization techniques can be attributed to the following ... 

Other alkylgold(III) compounds are [Au2(/r-X)2(CF3)4] (X = Br, I) synthesized by co-condensation of gold with CF3Br and CF3I, respectively, and may be sublimed at room temperature.1654 Trifluoromethylated compounds are potentially useful precursors for CVD studies as they are expected to show enhanced volatility.1655 m-[Au(CF3)2I(PMc3)] is formed in quantitative yield by oxidative addition of trifluoromethyl iodide to [Au(CF3)(PMe3)], the reaction is proposed to proceed via radical intermediates.1524,1656... 

The effect of aggregation of the subsurface solid phase on kerosene volatilization was studied by Fine and Yaron (1993), who compared the rate of aggregation in two size fractions of a vertisol soil the <1 mm fraction and 2 mm aggregates. The total porosity of these two fractions was similar (53% and 55% of the total volume, respectively). Differences in aggregation are reflected in the air permeability that is, their respective values were 0.0812 0.009 cm and 0.145 0.011 cm Figure 8.10 presents the volatilization of kerosene as affected by the soil aggregation, when the initial amount applied was equivalent to the retention capacity. The more permeable fraction releases kerosene faster and thus enhances volatilization. 

Fig. 8.10 Volatilization of kerosene from vertisol as affected by aggregate size. Reprinted from Fine P, Yaron B (1993) Outdoor experiments on enhanced volatilization by venting of kerosene components from soil. J Contam Hydrol 12 335-374. Copyright 1994 with permission of Elsevier...

Uses. As a gasoline blending component to enhance volatility as a constituent of liquid petroleum gas, which is usually a mixture of... 

T0268 Envirogen, Inc., VaporTech Enhanced Volatilization T0292 EnviroWall, Inc., EnviroWall Barrier T0309 Fixed Bed Soil Biofilters—General... 

Vaportech enhanced volatilization is designed to remove volatile contaminants from vadose zone soils in situ. The technology operates by injecting clean air around the perimeter of the contaminated area and withdrawing contaminated air from the middle. 

Soil vapor extraction is a commercially proven technology, and according to the vendor, the Vaportech enhanced volatilization method has been used in many full-scale remediations. The developer has performed held studies using hot air injection to further enhance the performance of this technology. The Vaportech technology is commercially available from Envirogen, Inc., formally MWR, Inc. 

There is no available information regarding the costs associated with the use of the Vaportech enhanced volatilization technology. 

If a compound has low volatility or if the parent mass cannot be determined, it may be possible to prepare a suitable derivative. The derivative selected should provide enhanced volatility, a predictable mode of cleavage, a simplified fragmentation pattern, or an increased stability of the molecular ion. 

There have been few mass spectral studies of pyrylium salts, possibly as a result of their low volatility. The examples reported so far have been concerned with the behaviour of alkyl- and aryl-substituted compounds under electron impact conditions. Information regarding the parent compound appears to be lacking. In the initial work, use was made of 2,4,6-trisubstituted pyrylium salts. The halides (iodides and bromides) were examined because of their enhanced volatility over the corresponding perchlorates and tetrafluorobo-rates <7lOMS(5)87>. 

---