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| The effects on the trichloroethylene sorption behaviors caused by the interactions between different sorption domains in model organic-mineral complexes |
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Abstract In order to research the sorption behavior effect of the complexes on organic pollutants, organic matters/minerals (C/M) montmorillonite-humic acid complexes and mixtures soil samples with different ratios were prepared to represent interactions and non-interactions between montmorillonite and humic acid respectively. A series of batch experiments were carried out to determine the sorption behavior of trichloroethylene (TCE) on the organic-mineral complexes and mixtures. Results showed that the adsorption isotherms of TCE fit the Freundlich adsorption model. By using the superposition of adsorption equation of montmorillonite and humic acid, the theoretical value of the adsorbed TCE amount in solid phase was calculated to represent the soil samples which were made up by non-interactions between montmorillonite and humic acid. The theoretical value of the adsorbed TCE amount in solid phase were all smaller than the actual values in the adsorption of complexes and mixtures, indicating that there were interactions between the two sorption domains in the complexes, which lead to some change in the properties of humic acid. And this enhanced the adsorption capability of complexes. At the same time, mixtures transformed into complexes to some extent, due to the participation of water in the process of isothermal adsorption. The adsorption capability of complexes and mixtures on TCE was enhanced with the increasing of C/M. The adsorption capability of complexes was higher than the mixtures when the C/M was lower than 0.08. This suggested that the changing of humic acid properties enhanced the adsorptioncapability of complexes. However, when the C/M was higher than 0.08, more organic matter were added on the patch, which would keep the original characteristics. This part of humic acid would cover up the influence taken by those denatured humic acid. Therefore, the adsorption capability of complexes and mixtures were almost the same. When the C/M of the complexes was fixed, the difference ?Qe, which calculated from the theoretical value of nonlinear superposition mode and the actual value, increased with the initial aqueous-phase solute concentration (C0) of TCE. This suggested that denatured humic acid had higher affinity for TCE than other components in the complexes. The sorption contribution of denatured humic acid increased with the increasing of C0.
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Received: 15 May 2012
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