Page 70 - Materials Chemistry, Second Edition

Site Assessment and Remedial Investigation 53

To estimate the solid concentration in equilibrium with the liquid concen-
tration (or vice versa), we have to determine the value of the partition coef-
ficient first. The following procedure can be used to determine the partition
coefficient for a soil–water system:

Step 1: Find K or S of the COC (Table 2.5).
ow
w
Step 2: Determine K using correlations given in Table 2.6 or Equation
oc
(2.28).
Step 3: Determine f of the soil.
oc
Step 4: Determine K using Equation (2.26).
p
Example 2.31: Solid–Liquid Equilibrium Concentrations

The aquifer underneath a site is impacted by tetrachloroethylene (PCE). A
groundwater sample contains 200 ppb of PCE. Estimate the PCE concentra-
tion adsorbed onto the aquifer material, which contains 1% of organic car-
bon. Assume the adsorption isotherm follows a linear model.

Solution:
(a) From Table 2.5, for PCE
log K = 2.6 → K = 398
ow
ow
(b) From Table 2.6, for PCE (a chlorinated hydrocarbon)
log K = 1.00(log K ) − 0.21
ow
oc
= 2.6 − 0.21 = 2.39
K = 245 mL/g = 245 L/kg
oc
Or, from Equation (2.28)
K = 0.63 K = 0.63(398) = 251 mL/g = 251 L/kg
ow
oc
(c) Use Equation (2.26) to find K :
p
K = f K oc
oc
p
= (1%)(251) = 2.51 mL/g = 2.51 L/kg
(d) Use Equation (2.25) to find S:
S = K C
p
= (2.51 L/kg)(0.2 mg/L) = 0.50 mg/kg

Discussion:

1. Equation (2.28) (K = 0.63 K ), which looks very simple, yields
ow
oc
an estimate of K (251 kg/L) that is comparable to the value (245
oc
L/kg) from using the correlation equation in Table 2.6.