Jul 17, 2009

Inverse temperature dependence of Henry's law coefficients for volatile organic compounds in supercooled water

Chemosphere
Karsten SiegWilhelm Püttmann

Abstract

Upon supercooling, water expels volatile organic compounds (VOC), and Henry's law coefficients are increasing concomitant with decreasing temperature. This unexpected observation was found by measuring the VOC partitioning between supercooled water and gas phase in the temperature range from -5 degrees C to -15 degrees C for benzene, toluene, ethlybenzene, m-, p-, o-xylenes (BTEX), methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE). Aqueous standard solutions were analyzed using a static headspace method in combination with gas chromatography/mass spectrometry (GC/MS). Dimensionless Henry's law coefficients (K(AW)) were calculated from measurements of the concentration of the VOCs in the headspace above the standard solutions at temperatures between -25 degrees C and 25 degrees C. The results show that the well known temperature dependence of Henry's law coefficients at temperatures above 0 degrees C is inversed upon decreasing the temperature below 0 degrees C and formation of supercooled water while decreasing the temperature to -15 degrees C. Upon further decrease of the temperature to -25 degrees C freezing of the supercooled water occurs. K(AW) values increase from 0.092 (benzene), 0.099 (toluene), 0.098 (eth...Continue Reading

Mentioned in this Paper

Crystal - Body Material
Ethyl tert-butyl ether
Organic Chemicals
Inversion Mutation Abnormality
Xylene
Ethylbenzene
Gas Chromatography-Mass Spectrometry
Uptake
Ethers
Benzene

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