Vapor /liquid equilibria of propionic acid /water system in the presence of different types of inorganic salts: effect of temperature and salt concentration

Isothermal vapor /liquid equilibrium data at 40 and 50 8C were obtained by using a headspace gas chromatography (GC) (one of the static methods) for the propionic acid /water system in the presence and absence of chloride salts. Propionic acid was salted-out in the presence of any chloride salt, in the following order: aluminum chloride /calcium chloride /sodium chloride /ammonium chloride. The effects of AlCl3, CaCl2, and NaCl, at the three concentration levels 0.2, 0.5 and 1.0 m, revealed an increase in salting out of propionic acid with the increase of salt concentration. No remarkable effect of temperature on the VLE data and consequently on the enhancement factor of propionic acid (i.e. the ratio of relative volatilities with and without salt) was observed. The modified Furter correlation was successful in correlating the effect of dissolved salts on the VLE of the systems studied.