Ion Exchange Capacity Of Ion Exchange Resin

Ion exchange capacity of ion exchange resin

The performance of ion exchange resin for ion exchange reaction is expressed in its "ion exchange capacity", that is, the number of milligram equivalent ions that can be exchanged per gram of dry resin or per milliliter of wet resin, meq/g(dry) or meq/mL(wet); When the ion is univalent, the number of milligrams equivalent is the number of milligrams of molecules (for bivalent or polyvalent ions, the former is the number of ions multiplied by the latter). It also has "total exchange capacity", "working exchange capacity" and "regenerative exchange capacity" three ways of expression.

1.The total exchange capacity, representing the total amount of chemical groups per unit number (weight or volume) of resin can carry out ion exchange reaction.

2. The working exchange capacity, indicating the ion exchange capacity of the resin under a certain condition, it is related to the type of resin and the total exchange capacity, as well as the specific working conditions such as the composition of the solution, flow rate, temperature and other factors.

3.Regeneration exchange capacity, indicating the exchange capacity of the regeneration resin obtained under a certain regeneration dose condition, indicating the degree of regeneration and recovery of the original chemical groups in the resin.

Generally, the regeneration exchange capacity is 50 to 90% of the total exchange capacity (generally controlled 70 to 80%), and the working exchange capacity is 30 to 90% of the regeneration exchange capacity (for the regeneration resin), the latter ratio is also known as the utilization rate of the resin.

In actual use, the exchange capacity of ion exchange resin includes the adsorption capacity, but the proportion of the latter varies with the structure of the resin. At present, it is still not possible to calculate separately. In the specific design, it is necessary to revise the empirical data and review it in actual operation.

The exchange capacity of ion resin is usually determined by inorganic ions. These ions are small in size and can freely diffuse into the resin to react with all the exchange groups within it. In practical application, the solution often contains polymer organic matter, their size is large, it is difficult to enter the resin micropores, so the actual exchange capacity will be lower than the value measured by inorganic ions. This situation is related to the type of resin, the structural size of the hole and the substance being treated.

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