engleski

Sorption of chlorophenolates in different types of natural sorbents

The sorption behaviour of chlorophenolates in natural sorbents having presumably a different type of organic matter was compared. A series of experiments was carried out in which three selected chlorophenols 2,4,6-trichlorophenol (TCP), 2,3,4,6-tetrachlorophenol (TeCP) and pentachlorophenol (PCP), under conditions favouring ionization of sorbates (pH>7.15), were sorbed in five samples of top soil, eight samples of terrestrial subsurface sediments and seven samples of marine sediments. The Freundlich isotherm coefficients Kf and 1/n were calculated and compared for all three chlorophenolates in each sorbent. The sorption coefficients Kf were positively related to the total sorbents organic matter (SOM) content with high linear correlation coefficients, but these relations were statistically significantly different in the three sorbent types tested. Isotherm non-linearities (1/n<1) were observed in all sorption experiments, and their evaluation also revealed considerable differences in sorption capacities of sorbents of different origin despite their apparently similar SOM fraction (0.5-12.2%). Comparison of thermodynamic sorption parameters (free-energy change) calculated from normalised sorption coefficient Kom in three sorbent types finally substantiated the observed differences in the sorption behaviour of chlorophenolates in different natural sorbents. These results directly contradict the partition concept of sorption based exclusively on hydrophobic interactions, which presumes that sorption intensity depends only on SOM content regardless of the sorbent type. For the sorption behaviour of ionic yet hydrophobic chlorophenolates a possibility of physical adsorption is indicated, which is likely to be based on more specific interactions rather than on hydrophobic partition, although this cannot be proved using sorption results obtained so far.

2;4;6-Trichlorophenol; 2;3;4;6-tetrachlorophenol; pentachlorophenol; chlorophenolates; sorption; soil; sediments

nije evidentirano