Features:

There is one unattractive feature which is common to all specific ion exchangers. As a matter of fact, the desired selectivity for certain ions is attained by introducing certain groups for which the counter ion has the affinity. As a result of this, the mobility of counter ions is greatly reduced. Therefore, the gain in selectivity is at the cost of rate of ion exchange. There is another problem which arises due to extreme specificity. It is difficult to replace the preferred counter ion except when it is replaced by H⁺ ions. This will mean that it may be difficult to regenerate the resin. In light of the above, one should choose a resin keeping in mind a compromise between selectivity, rate of ion exchange and ease of regeneration.