Page 178 - Materials Chemistry, Second Edition

Vadose Zone Soil Remediation 161

• Subsurface temperature = 25°C
• Dry bulk density of soil = 1.6 g/cm 3
• Total bulk density of soil = 1.8 g/cm 3

Estimate the extracted soil vapor concentration at the start of the soil-venting
project.

Solution:
(a) From Table 2.5, the following physicochemical properties of ben-
zene were obtained:

Molecular weight = 78.1
H = 5.55 atm/M
P vap = 95.2 mm-Hg
log K = 2.13
ow

(b) Use Table 2.4 to convert Henry’s constant to a dimensionless
value:

H = H/RT = (5.55)/[(0.082)(273 + 25)] = 0.23 (dimensionless)
*

Use Equation (2.28) to find K ,
oc
K = 0.63K = 0.63 (10 2.13 ) = (0.63)(135) = 85
ow
oc
Use Equation (2.26) to find K ,
p
K = f K = (0.03) (85) = 2.6 L/kg
oc
p
oc
(c) Use Equation (2.40) to estimate the soil vapor concentration of
benzene in equilibrium with this benzene concentration in soil:

  ( w ) + ( b ) K p + ()  
ρ
φ
a φ

 ×
X =   H H   G
 t ρ 


  (0.35)(0.45) + (1.6)(2.6) + (0.35)(1 45%) 
−

 
500 =   0.23 0.23  × G
 1.8 
 
So, G = 47.5 mg/L = 47,500 mg/m 3