Unit operation:

Ion exchange is firmly established as a unit operation. All over the world, numerous plants are in operation accomplishing the tasks that range from the recovery of metals from industrial wastes to the separation of rare earths and from catalysis of organic reactions to the decontamination of cooling water of nuclear reactors. In the laboratory, ion exchangers prove themselves as useful materials for accomplishing analytical separations. The ion exchange membranes find quite a good use in physiological chemistry and biophysics.  Ion exchange separation played a major role in the identification of trans-uranium elements by Glen T. Seaborg.  The identify of each element of 5f series was established beyond any doubt by the sequence of their appearance a analogous to the appearance of the corresponding 4f elements

The above applications clearly indicate that a variety of ion exchangers are available and these materials can be used for different applications. In view of this, it is important to understand the basic ion exchange mechanism, and a broad classification of ion exchangers. Ion exchange resins are synthesized through following different chemical routes. An idea about it could be had through illustrating the synthesis of some well- known ion exchange resins. The practical utility of an ion exchanger depends upon its properties, both chemical and physical. Another point which is important in this context is as to how the material is being operated. The discussion on ion exchangers will not be complete if we do not talk about some special type of ion exchangers viz. chelating resins and synthetic inorganic ion exchangers. Finally, a discussion on various types of applications will be taken up. It might be remembered that some of these uses may not be directly based on separations.

Objectives

After studying this Unit, you should be able to

• Define basic ion exchange mechanism,
• Categorize different types of ion exchangers,
• Define the synthesis of ion exchange resins,
• Elaborates the properties which characterize an ion exchanger,
• Define the operating methods for ion exchangers,
• Elaborates the behaviour of specific cation exchangers,
• Now a complete picture about the different types of synthetic inorganic ion exchangers and their advantages alongwith applications, and
• Describes different types of applications of ion exchangers.