Sorption and Desorption of Naphthalene by Soil Organic Matter

Abstract

lows multimechanistic dual-mode sorption (DMSM) or dual-reactive domain (DRDM) models (Xing and Pig-Nonlinear isotherm behavior has been reported for the sorption natello, 1997; White and Pignatello, 1999;Hu et al., of hydrophobic organic compounds (HOCs) in soil organic matter LeBoeuf and Weber, 2000a;Yuan and Xing, 2001 (SOM), but the exact mechanisms are unknown. Our objective was to provide insight into the sorption mechanism of HOCs in SOM by and references therein). studying the sorption-desorption processes of naphthalene in a min-According to these models, which consider organic materal soil, its humic fractions, and lignin. Additionally, humin and lignin ter in soil as a heterogeneous substance, SOM consists were used for studying the effects of temperature and cosolvent on of two types of amorphous domains. The domains are HOC sorption. All isotherms were nonlinear. The humin and lignin characterized as expanded and condensed, analogous to isotherms became more linear at elevated temperatures and with the rubbery and glassy synthetic polymers, respectively. addition of methanol indicating a condensed to expanded structural Sorption of HOCs to the expanded "rubbery-like" dophase transition. Isotherm nonlinearity and hysteresis increased in main generates linear isotherms due to partitioning while the following order: soil humic acid (HA) Ͻ soil Ͻ soil humin. Of the nonlinear isotherms are observed for the condensed samples, aliphatic-rich humin exhibited the largest degree of non-"glassy-like" domain due to adsorption in Langmuir-type linearity and had the highest sorption capacity for naphthalene. High nonlinearity and hysteresis in humin were most likely caused by its sorption sites. Although the dual mode sorption models condensed structure. A novel aliphatic, amorphous condensed conforhave been numerously cited in the sorption literatures, mation is proposed. This conformation can account for both high structural compositions of these domains (expanded or sorption capacities and increased nonlinearity observed for aliphaticcondensed) in SOM are not well understood (Cuypers rich samples and can explain many sorption disparities discussed in et al., 2002). the literature. This study clearly illustrates the importance of both Recent sorption (Chin et al., 1997; Perminova et al., aliphatic and aromatic moieties for HOC sorption in SOM.1999; Perminova et al., 2001) and spectroscopic studies (Xing and Chen, 1999;Johnson et al., 2001) have shown that the condensed domain is mainly attributed to aro-

Sorption of phenanthrene by nanosized alumina coated with sequentially extracted humic acids

“…The expanded domain is responsible for partitioning and isotherm linearity, while (Salloum et al 2002;Gunasekara and Xing 2003). Therefore, the later extracted HAs in this study had higher isotherm linearity (Fig.…”

Veterinary antibiotic sorption to agroforestry buffer, grass buffer and cropland soils

“…Freundlich coefficients presented here are given to indicate that our sorption results can be modeled using the Freundlich equation, and to provide a relative comparison between our data and previous studies. However, as discussed in Bowman (1981) and elsewhere (Chen et al 1999;Gunasekara and Xing 2003;Chefetz et al 2006), it is not possible to directly compare K f values when values of N are not equal.…”

Part V—sorption of pharmaceuticals and personal care products

“…Wershaw (1993) stated that the interactions of SOM with mineral could result in a membrane-like structure and the interface between SOM and mineral is hydrophobic. Gunasekara and Xing (2003) proposed a more condensed structure when organo-mineral complex was formed at lower HA loading, contributing to the enhanced nonlinearity.…”