Reducing energy required for separation

The use of a dissolved salt in place of a liquid component as the separating agent in extractive distillation has strong advantages in certain systems with respect to both increased separation efficiency and reduced energy requirements. A principal reason why such a technique has not undergone more intensive development or seen more than specialized industrial use is that the solution thermodynamics of salt effect in vapor-liquid equilibrium are complex, and are still not well understood. However, even small amounts of certain salts present in the liquid phase of certain systems can exert profound effects on equilibrium vapor composition, hence on relative volatility, and on azeotropic behavior. Also extractive and azeotropic distillation is not the only important application for the effects of salts on vapor-liquid equilibrium while used as examples, other potential applications of equal importance exist as well. 

In certain systems where solubility considerations permit, it is possible to use a salt dissolved into the liquid phase as the separating agent in place of the normal liquid. The attraction of the salt-effect distillation technique lies in its potential for greatly reduced energy requirements compared with conventional extractive and azeotropic distillation processes. 

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