Ion- exchange based method:

Problem:

Suggest the best possible ion- exchange based method for the following:

i) Separation of K⁺ from Na⁺

ii) Separation of Co²⁺ from Mg²⁺

iii) Recovery of Cs¹³⁷ from highly radioactive fission product waste.

iv) Separation of HCl from CH₃COOH.

State only the broad outlines.

Answer:

The best possible ion exchange based methods are

i) For the separation of K⁺ ion from Na⁺ ion is the use of dipicrylamine based specific cation exchanger. It is highly selective for K⁺ ion.

ii) The best alternative for the separation of Co2+ from Mg²⁺ is the use of a strong anion exchanger with HCl as the medium. From conc. HCl (more than 6M) Co²⁺ will be retained as anionic metal complex on the resin column and Mg²⁺ will pass as it does not form anionic metal chlorocomplex. Co²⁺ can be eluted by use of water.

iii) Since the solution is highly radioactive, the use of inorganic ion exchanger will be recommended. The ferrocyanide exchangers and zirconium phosphate are selective for Cs⁺ ion and therefore, either of them can be used for its recovery from fission products waste.

iv) Since HCl and CH₃COOH differ sufficiently in their degree of dissociation, the best alternative will be the use of ion exclusion technique. HCl will elute first followed by the elution of CH₃COOH.