Grand Canonical Monte Carlo study of sediment-contaminant interactions

James Farrell, Jing Luo

Research output: Contribution to journalConference article

Abstract

Contamination of aquifer and river sediments by hydrophobic organic compounds is a widespread problem that affects both the quality of potable water supplies, and the bioaccumulation of toxic compounds in aquatic organisms. Grand canonical Monte Carlo simulations were used to investigate the molecular-scale interactions between trichloroethylene (TCE) and sediment micropores. The energy changes accompanying TCE adsorption in the charged pore followed the same trend as those in the uncharged pore. Increasing pore widths were associated with an increasing contribution of entropically promoted adsorption. The negative entropy change accompanying TCE adsorption for pores widths of 12 Å and below was attributed to more restricted molecular motion in the charged pore due to the strong force field associated with the uncompensated charges. In the uncharged pore, the negative adsorption of water was promoted primarily by entropy effects. The lower entropy of adsorbed water resulted in lower water densities in the pore phase as compared to the bulk phase. In the charged pore, water adsorption was promoted by the highly exothermic heats of adsorption, but was nearly equally opposed by the loss in entropy upon adsorption. The net result was that the water density in the charged pores was similar to that in the bulk solution phase. The decrease in entropy accompanying water adsorption arises from the orienting effect of the charged surface sites. This is an abstract of a paper presented at the 224th ACS National Meting (Boston, MA 8/18-22/2002).

Original languageEnglish (US)
Pages (from-to)123-126
Number of pages4
JournalACS Division of Environmental Chemistry, Preprints
Volume42
Issue number2
StatePublished - Dec 1 2002
Event224th ACS National Meeting - Boston, MA, United States
Duration: Aug 18 2002Aug 22 2002

ASJC Scopus subject areas

  • Chemical Engineering(all)

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