Ion Exchange Design Supervised by: Prof. M. Fahim Done by: Samiya Saqer

Agenda: *Definition of Ion Exchange Process *Definition of Ion Exchange Materials *Design of Ion Exchange *Regeneration of Ion Exchangers *Applications

Ion Exchange Process Definition: Ion exchange is an exchange of ions between electrolytes or between electrolyte solution and a complex. In most cases the term is used to denote the process of purification of aqueous with solid ion exchangers.

Ion Exchange Materials Definition: Ion exchangers are insoluble solid materials, which carry exchangeable cations or anions. When the ion exchanger is in contact with an electrolyte solution, these ions are exchanged with an equivalent amount of other ions of the same sign.

Ion Exchange Materials Types of Ion exchangers: *Typical ion exchangers are ion exchange resins (functionalized porous or gel polymers), zeolites, clay, and soil humus. *Ion exchangers are either cation exchangers or anion exchangers.

*There are also amphotric exchangers that are able to exchange both cations and anions simultaneously.

Types of Ion Exchange Process *Ion exchange process can be accomplished by either a batch or a column method.

1) Batch System: *In this system, the resin and solution are mixed in a batch tank, the exchange is allowed to come to equilibrium, then the resin is separated from solution.

2) Column System: *In this system, a solution is passing through a column containing a bed of exchange resin.

Ion Exchange Design Helfferich-Glueckauf Model Suppose that the solid phase is initially form B and the liquid phase ion is A. The ion exchange can be presented as:

At steady state conditions, the spread of the boundary is given by:

Where: z A : The spread of the boundary H o, H p, and H f : The plate height contributions due to finite particle size, solid diffusion, and liquid-film diffusion

For the derivation of the model, it is assumed that: a) The separation factor is constant b) The linear-driving force rate laws for ion exchanger are valid c) The spreads caused by solid and liquid film are additive d) The flow in the fixed bed is ideal (plug flow)

In case of displacement of a single species, the effluent volume at which a given concentration X A emerges from the column is: Or in terms of time:

To calculate the breakthrough capacity: Where: q br : The breakthrough capacity in mass of solute per unit mass of the solid q o : Max A uptake of the solid phase achieved in bed

As the total mass of solute passed through the bed till break point is V br C o, where V br is the exit solution volume until the breakpoint, Where: C o : Initial concentration of B V o : The bed volume M out : The mass of the solute that was not absorbed by the bed solid

To calculate the mean exit concentration Finally, the so-called degree of column utilization can be calculated:

Ion Exchange Regeneration Ion exchange is a reversible process and the ion exchanger can be regenerated or loaded with desirable ions by washing with an excess of these ions.

After the feed solution is processed to the extent that the resin becomes exhausted and cannot accomplish any further ion exchange, the resin must be regenerated.

Applications Ion exchanged is widely used in the food, chemical & petrochemical, ground & potable water, metals finishing and a host of other industries.

References 1) 2) 3) Vassilis J. Inglezakis, Adsorption, Ion Exchange and Catalysis, Design of Operations and Environmental Applications,National Technical University of Athens (2006) 4) 5)