Recovery of Volatile Organic Compounds

S.6.7. Recovery of volatile organic compounds using liquid nitrogen... 

Headspace analysis is the method of choice for determining volatile organic compounds in soil [178-183]. A limitation of this method is the incomplete desorption of the contaminants in soil-water mixtures, but this problem can be overcome through the addition of methanol to the sample [181]. Good recoveries of volatile organic compounds in soils were obtained via thermal vaporisation of the sample followed by Tenax GC trapping and gas chromatography-mass spectrometry. 

Kawata et al. [ 128] have described the effects of headspace conditions on recoveries of volatile organic compounds from sediments and soils. Hewitt [129] compared three vapour partitioning headspace and three solvent extraction methods for the preparation of soil samples for volatile organic carbon determination in soils. Methanol extraction was the most efficient method of spiked volatile organic carbon recovery, which depended on the soil organic carbon content, the octanol-water partitioning coefficients of analytes and the extraction time. 

Bianchi et al. [134] and Yokouchi and Sano [135] obtained good recoveries of volatile organic compounds in soils employing thermal vaporisation followed by trapping on Tenax GC and analysis by gas chromatography-mass spectrometry. 

Wijmans JG, Goakey S, Wang X, Baker RW, and Kaschemekat JH, Membrane system for recovery of volatile organic compounds from remediation off-gases. Topical report for United States Department of Energy, April 1997. 

Majumdar S, Bhaumik D, Sirkar KK, and Simes G. A pilot-scale demonstration of a membrane-based absorption-stripping process for removal and recovery of volatile organic compounds. Environ Progress, 2001 20(1) 27-35. 

Steam Stripping and Batch Distillation for the Removal/Recovery of Volatile Organic Compounds... 

Ohlrogge K., Wmd J., Biinkmann T. 2010. Membranes for recovery of volatile organic compounds. In Drioli E. and Giomo... 

Membranes are among the most important industrial applications today, and every year, the use of this technology in processes such as water purification, industrial wastewater treatment, dehydration solvent recovery of volatile organic compounds, and protein concentration is increasing [1]. 

The process is of particular importance in the removal and recovery of volatile organic compounds (VOCs) and the removal of obnoxious odors or other trace impurities from air streams in connection with air pollution control. It is used to a lesser extent to recover hydrocarbons from natural, manufactured, and coke oven gases, although this was formerly a major application. 

Wijmans, J. G.. Kaschemekat, J., and Baker, R.W., 1991, A Membrane Process for the Recovery of Volatile Organic Compounds from Process and Vent Streams. Presented at the Air Waste Management Association 84th Annual Meeting and Exhibition, Vancouver, British Columbia, June 16-21. 

S. Sikdar, and L. Vane, Recovery of volatile organic compounds from emulsion of volatile organic compounds in water by pervaporation, US. Patent 6,039,878, assigned to the U.S.A. as represented by the US. Environmental Protection Agency, March 21,2000. 

The removal of volatile organic compounds (VOC) from air is most often accompHshed by TSA. Air streams needing treatment can be found in most chemical and manufacturing plants, especially those using solvents. At concentrations from 500 to 15,000 ppm, recovery of the VOC from steam used to regenerate activated carbon adsorbent thermally is economically justified. Concentrations above 15,000 ppm ate typically in the explosive range and... 

Solvent Recovery. Most of the activated carbon used in gas-phase applications is employed to prevent the release of volatile organic compounds into the atmosphere. Much of this use has been in response to environmental regulations, but recovery and recycling of solvents from a range of industrial processes such as printing, coating, and extmsion of fibers also provides substantial economic benefits. 

Croy Dewatering Environmental Services, Inc. (Croy), has developed the dual-phase recovery unit for the extraction of groundwater and the removal of volatile organic compounds (VOCs)... 

Terra Vac has developed Dual Vacuum Extraction (DVE) technology for the extraction of volatile organic compounds (VOCs) from groundwater and sod. DVE combines a soil vacuum extraction system with a groundwater recovery system. DVE wells operate below the water table and allow for extraction of VOC-contaminated groundwater and volatilization of VOCs in the soils above the water table. 

Stuart et al. [ 184] studied the analysis of volatile organic compounds in soil using an automated static headspace method. Recoveries increased in the or-... 

Various other workers have reported on the determination of volatile organic compounds in soils [186,187] and landfill soils [188]. Soil fumigants such as methyl bromide have also been determined by this technique [189]. Trifluoroacetic acid is a breakdown product of hydrofluorocarbons and hydrochlorofluorocarbon refrigerant products in the atmosphere and, as such, due to the known toxicity of trifluoroacetic acid, it is important to be able to determine it in the atmosphere, water and in soil from an environmental point of view [190]. In this method the trifluoroacetic acid is extracted from the soil sample by sulfuric acid and methanol, which is then followed by the derivatisation of it to the methyl ester. The highly volatile methyl ester is then analysed with a recovery of 87% using headspace gas chromatography. Levels of trifluoroacetic acid in soil down to 0.2 ng/g can be determined by the procedure. 

Recovery of volatile organic flavor compounds (ethyl acetate, EA ethyl propionate, EP ethyl butyrate, EB) Product recovery from biomass fermentation processes... 

D.J. Tranthim-Fryer, R.C. Hansson, K.W. Norman, Headspace/solid-phase microexlraction/gas chromatography-mass spectrometry a screening technique for the recovery and identification of volatile organic compounds (VOC s) in postmortem blood and viscera samples, J. Forensic Sci., 46, 934-946 (2001). 

Table 10.3 Comparative recoveries for the two-step K-D and EVACS approaches for a range of volatile organic compounds" (from 200 to 1 ml) [3]. Reprinted with permission from Ibrahim, E. A., Suffet, I. H. and Sakla, A. B., Anal Chem., 59, 2091-2098 (1987). Copyright (1987) American Chemical Society...

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