Effect of ionic strength on Henryʹs constants of volatile organic compound

The effect of ionic strength on Henryʹs law constants of volatile organic compounds was evaluated in this research using a gas chromatograph-headspace auto sampler system. Concentrations of sodium chloride from 0.1 mol/L to 1 mol/L were used to simulate various ionic strength in water at temperature of 20 °C. The salting-out coefficients at 10 °C for benzene, toluene, trichloroethylene and tetrachloroethylene were found to be 0.202, 0.240, 0.224 and 0.217 L/mol, respectively. The experimental results also showed that the ionic strength greater than 0.2M can lead to at least a 10% increase in Henryʹs constants, which in turn favors the partitioning of volatile organic compounds into the air phase. Typical sea water was simulated with 36% sodium chloride and tested at temperatures from 15 °C to 45 °C. It was found that the vanʹt Hoffʹs equation predicts the temperature effect very well for sea water. Henryʹs law constants for the studied volatile organic compounds in the typical sea water are about 30% higher than that in distilled water.