Isotherms of 1,3-dichlorobenzene

Figure 11.4 Vapor sorption isotherms of 1,3-dichlorobenzene on Woodbum soil at 20°C as a function of relative humidity (RH). Adapted from Chiou and Shoup (1985).

Figure 2. (a) Isotherm of 1,3-dichlorobenzene in Cheshire fine sandy loam soil suspension as a function of contact time. Adapted from data in ref 10. (b) Same data but in linear form for the high, medium, and low concentration regions, with linear regression lines and the Ap values shown. 

Figure 5. Isotherms of 1,3-dichlorobenzene in whole Pahokee peat soil (ATp = 340, N =0.8501) and its derivatives, humin (K = 464, N =0.7662) and humic acid ( p = 161, AT =0.936). Equilibration period, 48 h. The soil was extracted with sodium pyrophosphate. Adapted from data in ref. 11.

As noted in Section 9.3 (Fig. 9.8), the average Kioc values of 1,2-dichlorobenzene determined by Kile et al. (1995) for uncontaminated soil-water and sediment-water partitioning are about 300 and 500 L kg 1 oc, respectively. However, for heavily contaminated soils and sediments, these authors found significantly higher Kioc values (700 - 3000 L kg 1 oc), although isotherms were linear over a wide concentration range. Try to explain these findings. 

Figure 4. Contribution of hole-filling to total sorption calculated by the Freundlich slope method for 1,3-dichlorobenzene in (a) Cheshire fsl. and (b) Pahokee peat soil and its humin and humic acid fractions for a 48-h equilibration time. Data taken from isotherms in Figures 2 and 5.

Xiao et al. ° studied the adsorption of chlorobenzene and 1,3-dichlorobenzene at 313 to 453 K on a wood-based activated carbon, which was prepared by the activation of a char in CO2 at 1073 K. The adsorption isotherms for both the halogenated hydrocarbons are Type 1 of the BET classihcation (Figure 7.6). The amount adsorbed decreased systematically with the increasing temperature. The total volume of the halogenated hydrocarbon adsorbed was equal to the total pore volume of the carbon obtained from nitrogen adsorption at 77 K. The isosteric heats of adsorption of chlorobenzene calculated using the van Hoff isochore was 37 KJ/mol at an adsorption of 1 mmol/g and compared well with the heat of vaporization 35.19 KJ/mol. The adsorption appeared to be physical in nature involving micropores. The kinetics... 

Gas Chromatography. Extracts were analysed using a Carlo Erba 4160 Fractovap gas chromatograph equipped with a flame ionization detector. A Stabilwax-DA colunrn (60 m X 0.32 mm ID film thickness 0.5 pm Restek Corp.) was used to separate the components of the extracts. The GC oven temperature was programmed at 30°C for 30 secs, and then heated at 40°C/min to 60°C, and fi-om there at 3 C/min to 200 C. It was then held isothermally until the end of the run. The injector temperature was 250°C. Each extract (2 pi) was injected in the splitless mode and the injector chamber was purged after 30 sec. Quantitation of the chiral compoimds was achieved using 1,2-dichlorobenzene as an internal standard. A 25 pi aliquot of a 1000 mg/kg 1,2-dichlorobenzene standard was added to the solvent before extraction. 

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