Table 5-7. Calculated adsorption parameters of phenolic
 compounds in multi-compound system based on
 organic carbon.

--*------ --------- -- --- ;- ----- -- ------- ---
 Compounds log Ko b

 Phenol 2.161 0.936
 2,4-DCP 2.690 0.988
 PCP 4.064 0.710

 K values are in ml per gram organic carbon b
 bois the exponent in the Freundlich model: (X/m)=KF C


 The differences of sorption behavior between single-

compound and multi-compound systems are significant by t-

test analysis at alpha= 0.05. The Freundlich sorption

coefficients for mixed compounds are 1.5 to 3 times less

than those of single compounds. This phenomenon could have

been the result of either a co-solvent effect or a

competitive sorption effect. Although it is difficult to

identify the appropriate mechanism, the co-solvent effect

will have a greater influence on the co-solute (compounds

with lower solubility in common solvent) than on the co-

solvent (compounds with higher solubility in common solvent)

(Staples and Geiselmann, 1988). The common solvent is water

in this case. On the contrary, competitive sorption effect

should have a greater influence on sorption coefficients of

less hydrophobic compounds since they are less likely to win

the competition with more hydrophobic compounds for the

limited sorption sites. This observation provides a vehicle

to help identify the appropriate mechanism. Comparing the

corresponding Freundlich sorption coefficients from single-

compound and multi-compounds sorption studies, a list of