Thermodynamic investigation of trichloroethylene adsorption in water- saturated microporous adsorbents

James Farrell, Benjamin Hauck, Martin Jones

Research output: Contribution to journalConference article

19 Scopus citations

Abstract

Adsorption of trichloroethylene (TCE) in adsorbents containing hydrophilic and hydrophobic micropores was investigated in order to determine the mechanisms responsible for TCE adsorption on mineral solids. A high- pressure liquid chromatography method was used to measure TCE adsorption isotherms on three microporous adsorbents. Silica gel and zeolite type NaX were used as hydrophilic model adsorbents, and hexamethyldisilazane (HMDS)- treated silica gel was used as a model hydrophobic adsorbent. Batch uptake and desorption isotherms were also measured on the hydrophilic silica gel. Uptake of TCE by all three adsorbents was linear over the concentration range investigated. However, the silica gel desorption isotherm was highly nonlinear, as indicated by its Freundlich isotherm exponent of 0.58. Capillary phase separation into hydrophobic micropores was postulated as being responsible for the isotherm hysteresis. Supporting this hypothesis was the conformance of the TCE adsorption isotherm to Dubinin-Radushkevitch volume filling of micropores theory. The enthalpies for TCE adsorption on all three solids were determined by van't Hoff analysis of distribution coefficients measured over a temperature range from 5 to 90°C. The TCE adsorption enthalpies on the silica gel and HMDS silica gel were exothermic, but on the zeolite adsorption was endothermic. High exothermic adsorption enthalpies on the silica gel adsorbents indicated that TCE adsorption was occurring in hydrophobic micropores, and that adsorption on surfaces with large radii of curvature contributed only minimally to the total uptake. This indicates that the predominant mechanism for TCE adsorption on these mineral solids is not partitioning into the vicinal water layer.

Original languageEnglish (US)
Pages (from-to)1637-1642
Number of pages6
JournalEnvironmental Toxicology and Chemistry
Volume18
Issue number8
DOIs
StatePublished - Aug 3 1999
EventProceedings of the 1997 Symposium of the American Chemical Society on Mechanisms and Effects of Resistant Sorption Processes of Organic Compounds in Natural Particles - Las Vegas, NV, USA
Duration: Sep 7 1997Sep 11 1997

Keywords

  • Micropore adsorption
  • Silica gel
  • Trichloroethylene
  • Zeolite NaX

ASJC Scopus subject areas

  • Environmental Chemistry
  • Health, Toxicology and Mutagenesis

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