EXPERIMENTAL-STUDY OF OCTANOL-WATER PARTITION-COEFFICIENTS FOR 2,4,6-TRICHLOROPHENOL AND PENTACHLOROPHENOL - DERIVATION OF AN EMPIRICAL-MODEL OF CHLOROPHENOL PARTITIONING BEHAVIOR

The octanol-water partition coefficients (log K-ow) of 2,4,6-trichloro phenol and pentachlorophenol were determined as functions of pH, ionic strength and aqueous metal content. For both chlorophenols, the log K -ow exhibits pH dependence in the range pK(a)-1 < pH < pK(a) + 3. At l ower and higher pH values, the behaviour of the chlorophenols is indep endent of pH. The present data, in conjunction with that of pre-existi ng data, indicate that a linear relationship exists between log K-ow a nd log ionic strength of the aqueous solution for pentachlorophenol, a nd the data also suggest that aqueous metal-chlorophenolate complexati on can significantly alter the partitioning behaviour. The data report ed here was used to obtain an empirical model of the partitioning beha viour based on speciation of the aqueous chlorophenol. The model requi res knowledge of the low pH partitioning behaviour, as well as the aci dity constant for the particular chlorophenol of interest. Although K- ow values have been measured as a function of pH and/or ionic strength for only pentachlorophenol, the input parameters for our empirical mo del are readily accessible in the literature for many chlorophenols. T he model greatly expands our ability to quantify the hydrophobicity of chlorophenols, enabling accurate estimations of the pH and ionic stre ngth dependencies of the partitioning behaviour over a wide range of p H and ionic strength values of environmental interest. (C) 1998 Elsevi er Science Ltd. All rights reserved.