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ever detected was 3.75 mg/l of phenol from column #1 and 3.3
mg/l from column #2. Based on the Freundlich sorption
coefficients obtained from batch sorption studies, phenol
has a very low tendency to be adsorbed on this particular
type of sandy soil. Therefore it was assumed that the C
value of each compound was 3.75 mg/l for column #1 and 3.3
mg/l for column #2. Figure 5-7 was plotted based on the
normalized C/Co values, and the X-coordinates corresponded
to the intersections of the C/C =0.5 line with each
breakthrough curve being measured as the retardation
factors.
For the purpose of comparison, Equation (1-3) and
Equation (5-2) (Nkedi-Kizza et al., 1987) and the batch
sorption data were used to estimate the retardation factors.
Notice that Equation (1-3) assumes linear adsorption, i.e.,
the Freundlich exponent was assumed to be unity.
p KFA Cb-1
R = 1 + (5-2)
n
The calculated and measured retardation factors for
phenol, 2,4-DCP and PCP are listed in Table 5-11. They
agree with each other very well except for the PCP
retardation factor calculated from Equation (1-3). This
difference was caused by omitting the Freundlich exponent
since PCP adsorption deviates the most from linear.