Question

what are the similarities and differences between distillation, azeotropic distillation, extractive distillation and liquid-liquid extraction.

Answer 1

Similarities between distillation, azeotropic distillation, extractive distillation and liquid-liquid extraction:

• All these process come under mass transfer operations which involve transfer of mass of the more volatile component into the third component.
• The main motto of all these four operations is to seperate the components in the mixture to their purest forms.
• The temperature and pressure are maintained throughout the process so that equilibruim is established and most of the solute or more volatile component gets seperated.
• The choice of solvent made in all these four operations should be such that it is completely ineffective with the solute

Differences between distillation, azeotropic distillation, extractive distillation and liquid-liquid extraction:

• Although all these come under the mass transfer operation their principle method of sepreating the components of the binary mixture differs.
• Distillation uses the difference in the vapour pressure of the components present in the mixture to seperate them.
• At the atmosphere pressure , the vapour pressure of one the components becomes equal to it and gets boiled leaving behind the residue.
• In azeotropic distillation, the components in the binary mixture form azeotrope for which a third component such as organic phase is added to remove the more volatile component.
• Extractive distillation is similar to that of azetropic distillation but it forms no azeotrope . The relative volatilities of the components are nearer to unity and hence third component is added.
• Liquid - liquid extraction works on the principle of the distribution coefficient of the more volatile component and thus seperating the components based on the selectivity of raffinate and extract.

Thus these are the similarities and differences between distillation, azeotropic distillation, extractive distillation and liquid-liquid extraction.