How To Choose Ion Exchange Resin

The general principle for choosing ion exchange resins is to choose resins with large exchange capacity, easy regeneration, and durability. Specifically:

(1) Exchange capacity is an important indicator of the performance of ion exchange resins. The easier the exchange, the more ions can be adsorbed by the same volume of resin, and the larger the water production in one exchange cycle. Generally speaking, weakly acidic or weakly alkaline resins have a larger exchange capacity than strongly acidic or strongly alkaline resins. In addition, among similar resins, the exchange capacity varies due to the different crosslinking degrees of the resins. Generally, resins with low crosslinking degree have high exchange capacity; Resins with high cross-linking have low exchange capacity. Therefore, attention should be paid when selecting resins.

(2) Resin selection should be based on the properties of ions that need to be removed from the raw water. If it is only necessary to remove ions with weak exchange adsorption in water, strong acid or strong alkaline resins must be selected.

(3) Resin selection should be based on the water quality requirements of the effluent. If only a partial desalination system is needed, strong acidic cation resin and weak alkaline anion resin can be used in combination. For pure water or high-purity water systems that require complete desalination, strong acidic cation exchange resins with strong adsorption capacity and alkaline anion exchange resins should be used in combination to remove ions that are difficult to adsorb.

(4) Resin selection should be based on the composition of impurities in the raw water. If there are many organic compounds in the raw water or the radius for removing ions is large, a resin with a larger cross-linking pore diameter should be selected. Try to choose high-strength porous resin.

(5) The resin used for mixed beds is mostly a combination of strong acid and strong alkaline resins. However, it is important to consider the ease of layering during the regeneration of mixed bed resins. Therefore, it is required that the difference in wet true density between the two resins should be larger, generally not less than 15% to 20%. In addition, it is necessary to consider the high exchange flow rate and severe resin wear during the operation of the mixed bed, so wear-resistant resins should be selected.

(6) Resin selection should be based on the requirements of the desalination process. For example, in a dual chamber bed, strong and weak resins can be used in combination because weak resins are easy to regenerate and have lower quality requirements for regenerants. The regenerated liquid from strong resins can be used to regenerate weak resins, resulting in lower consumption of regenerants and lower water production costs.