Turbulence Effects on Volatilization Rates of Liquids and Solutes

Volatilization rates of neat liquids (benzene, toluene, fluorobenzene, bromobenzene, ethylbenzene, <i>m</i>-xylene, <i>o</i>-xylene, <i>o</i>-dichlorobenzene, and 1-methylnaphthalene) and of solutes (phenol, <i>m</i>-cresol, benzene, toluene, ethylbenzene, <i>o</i>-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 (<i>K</i>_L) for individual solutes are independent of whether they are in single- or multi-solute solutions. The gas−film transfer coefficients (<i>k</i>_G) 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 (<i>k</i>_L) can then be obtained from measured <i>K</i>_L and <i>k</i>_G values and solute Henry law constants (<i>H</i>). This approach provides a novel means for checking the precision of any <i>k</i>_L and <i>k</i>_G estimation methods for ultimate prediction of <i>K</i>_L. The improved <i>k</i>_G estimation enables accurate <i>K</i>_L predictions for low-volatility (i.e., low-<i>H</i>) solutes where <i>K</i>_L and <i>k</i>_G<i>H</i> are essentially equal. In addition, the prediction of <i>K</i>_L values for high-volatility (i.e., high-<i>H</i>) solutes, where <i>K</i>_L ≅ <i>k</i>_L, is also improved by using appropriate reference <i>k</i>_L values.