Vacuum extraction

Generally, high-temperature systems operate at temperatures above 1000°F (500-600°C), whereas low-temperature systems operate below 1000°F. High-temperature processes include (1) incineration, (2) electric pyrolysis, and (3) in situ vitrification. Low-temperature treatment systems include (1) soil roasting, (2) low-temperature incineration, (3) low-temperature thermal aeration, (4) infrared furnace treatment, and (5) low-temperature thermal stripping. 

High-temperature treatment systems involve destruction of contaminant(s) through complete oxidation, whereas low-temperature systems increase the rate of phase transfer (e.g., liquid phase to gaseous phase), and thus encourage contaminant partitioning from soil. Some of the disadvantages of heat treatment include its high cost and its ineffectiveness with some contaminants (e.g., low volatilization potential or incineration actually produces more toxic substances). 

Radio frequency (RF) heating is used for in situ thermal decontamination of soil. This process was originally developed in the 1970s for use in recovering hydrocarbons from materials such as oil shales and tar sands. The treatment is effective for volatile and semivolatile organics only. 

Vacuum extraction involves aeration followed by vacuum. It represents one of the most commonly used in situ treatment technologies. The technigue is effective when employed under buildings it is relatively cost effective but lengthy, and is not effective in water-saturated soils. 

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Of course the presence of a Hquid phase of hydrocarbon in a soil gives rise to vapor contamination in the vadose zone above the water table. This can be treated by vacuum extraction, and the passage of the exhaust gases through a biofilter (see above) can be a cheap and effective way of destroying the contaminant permanently. 

Hafnium metal is analy2ed for impurities using analytical techniques used for 2irconium (19,21,22). Carbon and sulfur in hafnium are measured by combustion, followed by chromatographic or in measurement of the carbon and sulfur oxides (19). Chromatographic measurement of Hberated hydrogen follows the hot vacuum extraction or fusion of hafnium with a transition metal in an inert atmosphere (23,24). 

Oxygen and nitrogen also are deterrnined by conductivity or chromatographic techniques following a hot vacuum extraction or inert-gas fusion of hafnium with a noble metal (25,26). Nitrogen also may be deterrnined by the Kjeldahl technique (19). Phosphoms is determined by phosphine evolution and flame-emission detection. Chloride is determined indirecdy by atomic absorption or x-ray spectroscopy, or at higher levels by a selective-ion electrode. Fluoride can be determined similarly (27,28). Uranium and U-235 have been determined by inductively coupled plasma mass spectroscopy (29). 

Principal Option for Containment/ Recovery Excavation Vacuum extraction Temporary cap/cover Hydraulic modification No action Groundwater pumping Subsurface drains Hydraulic barriers Low permeability barriers No action Overflow/underflow containment (i.e. oil booms) Run off/run on control Diversion/collection No action Capping/ nsulation Operations modifications Gas collection/removal No action... 

The most commonly used remediation technique for the recovery of organic contaminants from ground water has been pump- and-treat, which recovers contaminants dissolved in the aqueous phase. In this regard, the application of carbon adsorption has found extensive, but not exclusive use. Vacuum extraction (also called soil venting) has also become popular for removal of volatile organic contaminants from the unsaturated zone in the gaseous phase. Both of these techniques can, in the initial remediation phase, rapidly recover contaminants at concentrations approximately equal to the solubility limit (pump-and-treat), or the maximum gas phase concentration of the contaminant (vacuum extraction). The... 

Despite the potential problems, two recent studies provide positive results. Matthews et al. (2000) analyzed the 5D of fluid inclusions in present-day cave carbonates from Soreq cave (Israel) using the method of thermal vacuum extraction and standard techniques on cave pool water from the same cave to estimate isotopic fractionation during measurement (Aex = 5Dextracted water - 8Dcave water). After subtracting Aex from 5D... 

Albertus, Frater], Simple vacuum extraction method. Alchem Lab Bulls 2, no. 1 (1970). rhttp //www.spagyria.com/alb.zipl. 

Modification of a simple vacuum extraction method. Parachemy 6, no. 1 (Winter 1978) 515-. 

The vacuum extraction process involves using vapor extraction wells alone or in combination with air injection wells. Vacuum blowers are used to create the movement of air through the soil. The air flow strips the VOCs from the soil and carries them to the surface. Figure 18.14 shows the flow diagram for such a process. During extraction, water may also be extracted along with vapor. The mixture should be sent to a liquid-vapor separator. The separation process results in both liquid and vapor residuals that require further treatment. Carbon adsorption is used to treat the vapor and water streams, leaving clean water and air for release, and spent GAC for reuse or disposal. Air emissions from the system are typically controlled by adsorption of the volatiles onto activated carbon, by thermal destruction, or by condensation. 

The vacuum extraction method has been effectively applied to removing VOCs with low organic carbon content from well-drained soil, although it may also be effective for finer and wetter soils, but with comparatively slower removal rates. There are generally significant differences in the air permeability of various strata, which can influence process performance. Contaminants with low vapor pressure or high water solubilities are difficult to remove. 

Soil vacuum extraction is cost-effective if the volume of contaminated soil exceeds 382 m3 (500 yd3), and if the contaminated area is more than 6 m (20 ft) deep otherwise, soil excavation and... 

The remedial technologies83-85,90-93 described in previous sections for gasoline release are applicable, for the most part, for remediation of DNAPLs. For example, the pumping or trench method for free products, vacuum extraction, biodegradation, pumping and treatment, soil flushing, and soil excavation and treatment are suitable for cleanup of various phases of DNAPLs. Again, because of... 

A further development is the combination of the pin barrel extruder system with that of the Transfermix (see under EXTRUDERS, MIXERS). The combined system is known as Pinconvert and is available with or without vacuum extraction. 

In moulds for complex product shapes it can be advantageous to provide vacuum extraction to the cavities so that air and evolved gases can be removed from the mould cavity, before and during vulcanisation to ensure complete cavity fdling, and a product without air (gas) blemishes. 

Presses with vacuum extraction fitted to extract gases from moulding cavities eliminate moulding faults arising from air entrapment, or gases generated during vulcanisation. These presses are... 

A shorter method of hydrolysis which may work as well follows dissolve 20 g alkaloid in 300 ml methanol and 300 ml 40% KOH and reflux two hours under N2 (if possible). Cool, saturate with C02 and evaporate in vacuum. Extract the residue with hot ethanol three times and dry, evaporate in vacuum the combined ethanol extracts to get (I). 

Dissolve 0.536 g (I) in 10 ml freshly distilled POCl3 stir and add 416 mg powdered, freshly sublimed PCl5. Hold two minutes at room temperature, two minutes at 90°, and evaporate in vacuum. Extract the residue with hexane to give the lysergic acid chloride-HCl (can also extract the reaction mixture with hexane instead of evaporating in vacuum). Alternatively, use 6 ml POCl3 and 240 mg SOCI2 and heat three minutes at 90° to get the acid chloride. To 5 g of the acid chloride add 1.4 ml DEA in 50 ml methylene chloride and coo to 0°. Stir and add 27.5 ml pyridine and stir one-half hour at 0°. Warm to room temperature and stir 1 Vi hours evaporate in vacuum to get... 

Two-phase vacuum extraction (TPVE) in hazardous waste management, 25 845 Two-phase zeolite-based alkylation, 23 331-332... 

The radius of influence of a vacuum extraction system, if necessary, to recover sparged vapors and... 

The vacuum-vaporized well technology is a proprietary process that combines vacuum extraction, bioremediation, and soil flushing to mobilize contaminants in the vadose, capillary, and saturated zones. A schematic of the double-screened well with the equipment contained within is shown in Figure 10.12. 

T0655 Remediation Service International, Spray Aeration Vacuum Extraction (SAVE) System... 

T0712 SIVE Services, Steam Injection and Vacuum Extraction (SIVE)... 

T0718 Smith Technology Corporation, Two-Phase Vacuum Extraction... 

T0778 Terra Vac, Inc., Sparge VAC T0779 Terra Vac, Inc., Vacuum Extraction... 

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