APPLICATION OF HEADSPACE ANALYSIS TO THE STUDY OF SORPTION OF HYDROPHOBIC ORGANIC-CHEMICALS TO ALPHA-AL2O3

The sorption of hydrophobic organic chemicals (HOCs) to alpha-Al2O3 wa s investigated with a headspace analysis method. The semiautomated hea dspace analyzer gave rapid, precise, and accurate results for a homolo gous series alkylbenzenes even at low percentages of solute mass sorbe d (3-50%). Sorption experiments carried out with benzene alone indicat ed weak interactions with well-characterized aluminum oxide, and a sol ids concentration effect was observed. When the sorption coefficients for benzene alone obtained by headspace analysis were extrapolated up to the solids concentrations typically used in batch sorption experime nts, the measured sorption coefficients agreed with reported sorption coefficients for HOCs and sediments of low fractional organic carbon c ontent. Sorbed concentrations increased exponentially with aqueous con centration in isotherms with mixtures of alkylbenzenes, indicating sol ute-solute interactions at the mineral surface. Sorption was, however, greater than predicted for partitioning of a solute between its pure liquid phase and water, indicating additional influences of the surfac e and/or the structured liquid near the mineral surface.