Sorption behaviour of some chlorophenols in lake aquatic humic matter

The sorption behaviour of 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP) and pentachlorophenol (PCP) with an aquatic humic sorbent (HS) was examined in their single and mixed solutions at different acidities (pH 3, 5.5 and 7). The binding capacities and equilibrium coefficients (K-OC) obtained were fairly close to the literature values but still underline HS's structural and steric influence on the sorption. The most acidic carboxylic (COOH) groups of the HS structure have unquestionably an essential role in the sorption. The amounts of different chlorophenols bound onto the constant quantity of the aquatic HS were in reality very low demonstrating that the amount of the dissolved organic carbon (DOC) in the environment plays a greater role than the value of K-OC. The ability of the aqueous phase to force chlorophenols to associate with the HS becomes at more neutral acidities weaker and weaker and other binding mechanisms become favoured in comparison to hydrogen or hydrophobic bonds. Sorption isotherms were constructed from sorption data. and conformity to a linear model, non-linear Freundlich equation and Langmuir equation was checked. (C) 2002 Elsevier Science B.V. All rights reserved.