Detailed sorption isotherms of pentachlorophenol on soils and its correlation with soil properties.

Insight into the sorption mechanism of pentachlorophenol (PCP) was gained by constructing highly detailed isotherms over the widest possible concentration range. Using the dual-mode model, sorption isotherms of PCP were accurately predicted, the sorption capacities were determined, and the mechanisms of adsorption (hole-filling) and partitioning were elucidated. Sorption-desorption hysteresis in the present study was manifested to some significant degree in 10 soils with different properties. Such hysteresis might result from the pore deformation and entrapment of PCP molecules within organic matter. Total nitrogen in soils also has its contribution in these kinds of processes. Correlations of stepwise regression equations obtained confirm that pH, soil organic carbon and organic carbon fractions, and particle size distribution are the main factors responsible for the sorption and desorption hysteresis processes. These factors worked in concert in influencing the fate of PCP sorption-desorption in soil. The empirical models developed in this study accurately predict PCP sorption and desorption hysteresis phenomena for the soils that were investigated.