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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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23.1 Natural attenuation <strong>of</strong> chlorinated solvents 1579<br />

Constituent<br />

CAS<br />

#<br />

Molecular<br />

weight<br />

M W,<br />

g/mol Ref<br />

D air,<br />

cm 2 /s<br />

Diffusion coefficients<br />

in air in water<br />

Ref<br />

D wat,<br />

cm 2 /s<br />

Ref<br />

log Koc<br />

(@20-25°C)<br />

Partition<br />

log(L/kg)<br />

Dichloroethane, 1,1- 75-34-3 98.96 22 7.42E-02 22 1.05E-05 22 1.76 22<br />

Dichloroethane, 1,2- 107-06-2 98.96 22 1.04E-01 22 9.90E-06 22 1.76 22<br />

Dichloroethene, cis-1,2- 156-59-2 96.94 22 7.36E-02 22 1.13E-05 22 1.38 c<br />

Dichloroethene, 1,2-trans 156-60-5 96.94 22 7.07E-02 22 1.19E-05 22 1.46 22<br />

Dichloromethane 75-09-2 85 22 1.01E-01 22 1.17E-05 22 1.23 22<br />

Tetrachloroethane, 1,1,2,2- 79-34-5 168 22 7.10E-02 22 7.90E-06 22 0.00 22<br />

Tetrachloroethene 127-18-4 165.83 22 7.20E-02 22 8.20E-06 22 2.43 28<br />

Trichlorobenzene, 1,2,4- 120-28-1 181.5 22 3.00E-02 22 8.23E-06 22 3.91 22<br />

Trichoroethane, 1,1,1- 71-55-6 133.4 22 7.80E-02 22 8.80E-06 22 2.45 22<br />

Trichloroethane, 1,1,2- 79-00-5 133.4 22 7.80E-02 22 8.80E-06 22 1.75 28<br />

Trichloroethene 79-01-6 131.4 24 8.18E-02 a 1.05E-04 b 1.26 d<br />

Trichlor<strong>of</strong>luoromethane 75-69-4 137.4 22 8.70E-02 22 9.70E-06 22 2.49 22<br />

Vinyl chloride 75-01-4 62.5 22 1.06E-01 22 1.23E-05 22 0.39 26<br />

a<br />

Calculated diffusivity using the method <strong>of</strong> Fuller, Schettler, and Giddings [from Reference 25]<br />

b<br />

Calculated diffusivity using the method <strong>of</strong> Hayduk and Laudie and the reference 25<br />

c<br />

Calculated using Kenaga and Goring Kow/solubility regression equation from reference 25 and Kow data from reference<br />

26, log (S, mg/L) = 0.922 log(Kow) + 4.184 d<br />

d<br />

Back calculated from solubility [see note c, based on Kow from reference 26 and method from reference 27,<br />

log(Koc) = 0.00028 + 0.938 log (Kow)] [From RBCA Chemical Database. Copyright © 1995-1997 Groundwater Services, Inc. (GSI). Reprinted with<br />

permission.]<br />

23.1.2.7 Hydrolysis and dehydrohalogenation<br />

Hydrolysis and dehydrohalogenation reactions are the most thoroughly studied abiotic attenuation<br />

mechanisms. In general, the rates <strong>of</strong> these reactions are <strong>of</strong>ten quite slow within the<br />

range <strong>of</strong> normal ground-water temperatures, with half-lives <strong>of</strong> days to centuries. 29,30 Hydrolysis<br />

is a substitution reaction in which a compound reacts with water, and a halogen<br />

substituent is replaced with a hydroxyl (OH - ) group resulting in the formation <strong>of</strong> alcohols<br />

and alkenes after: 31,32<br />

RX + HOH → ROH+HX [23.1.13]<br />

H 3C-CH 2X → H 2C=CH 2 +HX [23.1.14]<br />

The likelihood that a halogenated solvent will undergo hydrolysis depends in part on<br />

the number <strong>of</strong> halogen substituents. More halogen substituents on a compound will decrease<br />

the chance for hydrolysis reactions to occur, 29 and will therefore decrease the rate <strong>of</strong><br />

the reaction. In addition, bromine substituents are more susceptible to hydrolysis than chlo-<br />

Ref

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