Solubility-Normalized Combined Adsorption-Partitioning Sorption Isotherms for Organic Pollutants

Abstract

Equilibrium sorption isotherms were measured for five different low-polarity organic compounds (benzene, trichloroethene, 1,2- and 1,4-dichlorobenzene, and phenanthrene) over a wide concentration range. The investigated sorbents can be grouped into the following three classes: (1) humic soil organic matter, which shows linear sorption isotherms (solely partitioning, as observed in the peat sample); (2) carbon materials, which were thermally altered (due to their natural history or industrial production) and thus contain a high specific surface area and exhibit nonlinear isotherms, and (3) pure engineered microporous materials (e.g., zeolites and activated carbon), where adsorption is solely due to a pore-filling process. Sorption of all compounds was fitted very well by the Polanyi-Dubinin-Manes (PDM) model, which for sorbents containing humic organic matter (e.g., peat) was combined with linear partitioning. Both the partitioning and the Polanyi-Dubinin-Manes model predict unique sorption isotherms of similar compounds if the solubility-normalized aqueous concentration is used. In addition, an inverse linear relationship between the distribution coefficient (Kd) and water solubility, which was very well confirmed by the data, is obtained. This also leads to unit-equivalent Freundlich sorption isotherms and explains the often observed apparent correlation between sorption capacity at a given concentration (e.g., Freundlich coefficient) and sorption nonlinearity (Freundlich exponent).

Sorption of phenanthrene and benzene on differently structural kerogen: Important role of micropore-filling

“…Some studies have indicated that porosity and surface properties of NOM play a significant role in controlling the sorption (Kleineidam et al, 2002;Pignatello, 2012;Ran et al, 2002Ran et al, , 2004Ran et al, , 2013.…”

Fate and Determination of Triazine Herbicides in Soil

“…partitioning, non-covalent and covalent binding) is usually evaluated by sorption isotherms conforming to various theoretical models: Freundlich, Langmuir, Polanyi-Dubinin-Manes, etc. (Aboul-Kasim & Simoneit, 2001;Kleineidam et al, 2002). The most frequently used method to obtain the experimental data for isotherm construction remains the batch equilibrium method (Celano et al, 2008;Kleineidam et al, 2002;Konda et al, 2002;Kovaios et al, 2006;Lima et al, 2009;Ling et al, 2006;Stipičević et al, 2009).…”

“…(Aboul-Kasim & Simoneit, 2001;Kleineidam et al, 2002). The most frequently used method to obtain the experimental data for isotherm construction remains the batch equilibrium method (Celano et al, 2008;Kleineidam et al, 2002;Konda et al, 2002;Kovaios et al, 2006;Lima et al, 2009;Ling et al, 2006;Stipičević et al, 2009). Other approaches are by chromatographic estimation (Bermudez-Saldana et al, 2006) or indirectly by structural descriptors (Schüürmann et al, 2006).…”

“…In batch equilibrium method, several variables may influence the process of sorption a n d h a v e t o b e c a r e f u l l y o p t i m i s e d : o r g a n i c solvent content, ionic strength and pH, solid/solution ratio, sorption time (Celano et al, 2008;Kleineidam et al, 2002;Kovaios et al, 2006;Prosen & Zupančič-Kralj, 2000;Prosen et al, 2007). After the equilibrium is reached, the solution has to be separated from the sorbent either by centrifugation or filtration (Kleineidam et al, 2002). By using the latter, another potential source of error is introduced as more hydrophobic compounds may bind to certain types of filters.…”

Evidence for in situ degradation of mono-and polyaromatic hydrocarbons in alluvial sediments based on microcosm experiments with 13C-labeled contaminants

“…The microbial degradation of aromatic hydrocarbons is hampered for three reasons: Firstly, because of the high activation energy needed to chemically attack aromatic rings (Boll et al, 2002), secondly by the substances' toxicities towards bacteria (Jonker et al, 2006;Loibner et al, 2004), and thirdly because aromatic hydrocarbons have a tendency to sorb on hydrophobic surfaces. This tendency is increasing with the number of their aromatic rings (Kleineidam et al, 2002;Kubicki, 2006). Sorption and poor solubility in water makes the major fraction of PAHs inaccessible for bacterial degradation (Bosma et al, 1997;Volkering et al, 1992).…”