Linear solvation energy relationships used to evaluate sorption mechanisms of volatile organic compounds with one organomontmorillonite under different humidities
Journal
Journal of Chemical and Engineering Data
Journal Volume
56
Journal Volume
56
Journal Issue
12
Journal Issue
12
Pages
4950-4955
Start Page
4950
End Page
4955
ISSN
15205134
Date Issued
2011-12-08
Author(s)
Abstract
Organic-cation-modified clays are usually used as sorbents to reduce the spread of organic contaminants in remediation or landfill sites and to remove them at contaminated sites. To effectively design organomontmorillonite to remove volatile organic compounds (VOCs) and predict the fate of VOCs in the environment, the sorption equilibrium and mechanisms of VOCs on organomontmorillonite under different humidities are needed to be studied. In this study, organomontmorillonite was synthesized through exchanging inorganic cations by hexadecyltrimethyl ammonium (HDTMA) into montmorillonite. The surface area of organomontmorillonite was smaller than the unmodified clay because of the incorporation of organic cations into interlayers of clay. As compared to sorption coefficients in montmorillonite under different humidities, surface adsorption on organomontmorillonite surface and partition into the incorporated HDTMA in organomontmorillonite both play roles on the sorption process. The sorption coefficients of VOC vapors on organomontmorillonite were further characterized using a linear solvation energy relationship (LSER). The fitted LSER equations were obtained by a multiple regression of the sorption coefficients of 22 probe chemicals against their solvation parameters. The coefficients of the five-parameter LSER equations show that organomontmorillonite interacts with VOC molecules mainly through dispersion, partly through dipolarity/polarizability and hydrogen-bonds and with negative π-/n-electron pair interaction. The interaction analysis by LSERs suggests that the potential predominant factors governing the sorption of VOCs are dispersion interactions under all tested humidity conditions, whereas hydrogen-bond interactions or both interactions dominate the sorption process with the increase of relative humidity. The derived LSER equations successfully fitted the sorption coefficients of VOCs on organomontmorillonite. A better understanding of the effect of relative humidity on the organo-inorganic complexes sorption mechanism via the LSER approach is important to the design of the toxic-vapor removal and the assessment of organic contaminants in the environment.
Type
journal article