SORPTION BEHAVIOR OF SOME CHLOROPHENOLS IN NATURAL SORBENTS .1. VALIDITY OF THE PARTITION MODEL FOR SORPTION OF PHENOLATES

In order to verify the validity of the partition model for describing the sorption behaviour of hydrophobic but ionizable polar compounds in natural sorbents, a series of experiments was carried out in which three chlorophenols: 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol, were sorbed in 14 different soil and sediment samples. Freundlich isotherm coefficients K-f and 1/n were calculated for all three compounds in ail sorbents and compared with those favouring phenolate forms. The sorption coefficients K-f were closely related to the total sorbent organic matter content with a high correlation coefficient. However, isotherm non-linearities were observed in almost all experiments. The removal of the sorbent organic matter from the three tested sorbents drastically decreased the sorption intensity in two of them, but considerably increased it in the third, indicating that interaction with the mineral surface could be much stronger than sorption in the organic phase. These results indicate that the simplified partition concept used for the sorption of non-polar compounds might not offer an adequate description of the sorption behaviour of chlorophenolates in natural sorbents.