Sorption Equilibrium of a Wide Spectrum of Organic Vapors in Leonardite Humic Acid:  Modeling of Experimental Data

Abstract

In a recent publication we presented experimental Leonardite humic acid/air partition coefficients for 188 polar and nonpolar organic compounds measured with one consistent method. In this paper these experimental data are evaluated with various model predictions. For the PcKocWIN model some major shortcomings become apparent. The octanol-based Karickhoff-model exhibits a good performance for the nonpolar compounds but not for the polar ones. A good description of the whole data set is achieved with a polyparameter linear free energy relationship (pp-LFER) that explicitly accounts for the nonpolar (van der Waals and cavity formation) and polar (electron donor/acceptor) interactions between the sorbate molecule and the sorbent phase. With this pp-LFER model, most of the humic acid/air partition coefficients could be predicted within a factor of 2. The pp-LFER model also successfully predicts organic-C/water partition coefficients (K(ioc)) collected from the literature when it is combined with a pp-LFER for air/water partition coefficients. This supports our earlier conclusion that the thermodynamic cycle is applicable in the humic acid/water/air system. Based on our experimental data, we present a pp-LFER-model for humic acid/air and humic acid/water partitioning at any ambient temperatures.

Characterization of the Partitioning of Gaseous Solutes Into Humic Acid with the Abraham Model and Temperature‐Independent Equation Coefficients

“…Similarly good agreements were obtained for the other four temperatures for which we had temperaturespecific correlations. Niederer et al [24] did note a linear relationship between their calculated equation coefficients for the modified Abraham model and 1/T. The computational methodology we suggest by Eq.…”

“…Niederer et al [36] determined the Leonardite humic acid/ air partition coefficients of 188 nonpolar and polar organic compounds at temperatures between 5 and 75 8C using a dynamic flowthrough technique. For four of the eight temperatures studied, the authors [24] tabulated the equation coefficients for a modified version of the Abraham model. At 288.15 K and 98% relative humidity, the derived correlation was [24] …”

“…For four of the eight temperatures studied, the authors [24] tabulated the equation coefficients for a modified version of the Abraham model. At 288.15 K and 98% relative humidity, the derived correlation was [24] …”

“…Our proposed method of analyzing the experimental log K LHA data differs from that of Niederer et al [24] in that we have modified Eq. (2) of the Abraham model so that experimental data measured at different temperatures can be included into a single correlation expression.…”

Part IV—sorption of hydrophobic organic contaminants

“…Therefore, both SOM and HOC properties should be considered to predict HOC behavior in the environment. A polyparameter, linear free energy relationship has been established to account for polar and nonpolar interaction between HOCs and HS in air (Niederer et al 2006(Niederer et al , 2007. Similar study is urgently needed for HOC sorption modeling from aqueous phase to HS.…”