Table 5-10. Desorption regression parameters of phenolic
 compounds in multi-compound systems.
...........................................................

Compounds pH log KFD ST.DEV.+ b ST.DEV. R2

[Aquifer material]
 Phenol 5.01 -1.952 0.068 0.535 0.089 0.948
 2,4-DCP 5.01 -1.380 0.052 0.744 0.068 0.983
 PCP 5.01 -1.234 0.036 0.183 0.045 0.891
...........................................................
[Aquifer material + sludge]
2ppm NaN3
 Phenol 5.01 -1.417 0.031 0.825 0.040 0.995
 2,4-DCP 5.01 -1.057 0.009 0.837 0.012 0.998
 PCP 5.01 -0.920 0.032 0.357 0.048 0.965
 6ppm NaN3
 Phenol 5.01 -1.481 0.079 1.009 0.102 0.980
 2,4-DCP 5.01 -1.033 0.014 0.647 0.020 0.998
 PCP 5.01 -0.887 0.042 0.374 0.062 0.948
 Average
 Phenol -1.449 0.917
 2,4-DCP -1.045 0.742
 PCP -0.904 0.366

 + Log standard deviation of log KFA values


 Freundlich adsorption and desorption isotherms are

presented in Figure 5-1 through Figure 5-6. Statistical

analyses (t-test at alpha= 0.05) indicated that the

Freundlich coefficients (KFA and K D) of phenolic compounds

in general are significantly different between adsorption

and desorption. However, further analyses on each compound

showed that this difference was mainly contributed by PCP

(no difference for 2,4-DCP, different for phenol at alpha=

0.05 but no difference at alpha= 0.01). This suggested that

significant amounts of PCP were irreversibly held onto the

sorbents, but not phenol and 2,4-DCP. A mass balance

calculation confirmed this observation. Approximately 10%,

30% and 90% of adsorbed phenol, 2,4-DCP and PCP,