The adsorption of aromatic compounds by smectite exchanged with tetramethylammonium (TMA) has been studied. Aromatic compounds adsorbed by TMA-smectite are assumed to adopt a tilted orientation in a face-to-face arrangement with the TMA tetrahedra. The sorptive characteristics of TMA-smectite were influenced strongly by the presence of water. The dry TMA-smectite showed little selectivity in the uptake of benzene, toluene and xylene. In the presence of water, TMA-smectite showed a high degree of selectivity based on molecular size/shape, resulting in high uptake of benzene and progressively lower uptake of larger aromatic molecules. This selectivity appeared to result from the shrinkage of interlamellar cavities by water.
Volatilization rates of neat liquids (benzene, toluene, fluorobenzene, bromobenzene, ethylbenzene, m-xylene, o-xylene, o-dichlorobenzene, and 1-methylnaphthalene) and of solutes (phenol, m-cresol, benzene, toluene, ethylbenzene, o-xylene, and ethylene dibromide) from dilute water solutions have been measured in the laboratory over a wide range of air speeds and water-stirring rates. The overall transfer coefficients (K(L)) for individual solutes are independent of whether they are in single- or multi-solute solutions. The gas-film transfer coefficients (kG) for solutes in the two-film model, which have hitherto been estimated by extrapolation from reference coefficients, can now be determined directly from the volatilization rates of neat liquids through a new algorithm. The associated liquid-film transfer coefficients (kL) can then be obtained from measured K(L) and kG values and solute Henry law constants (H). This approach provides a novel means for checking the precision of any kL and kG estimation methods for ultimate prediction of K(L). The improved kG estimation enables accurate K(L) predictions for low-volatility (i.e., low-H) solutes where K(L) and kGH are essentially equal. In addition, the prediction of K(L) values for high-volatility (i.e., high-H) solutes, where K(L) approximately equal to kL, is also improved by using appropriate reference kL values.
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