The weak acid cation exchange resin is the type of ion exchange resin with functional group of carboxylic acid group (-COOH). 

A weakly acidic cation exchange resin that behaves like a weak acid in water. Therefore, its ability to decompose neutral salts is weak (ie, it is difficult to react with salts of strong acid anions such as SO42-, Cl-). It can only react with weakly acidic salts (salts with alkalinity), so it can handle large alkalinity water with weak acid H-type exchange resin.

Since the weakly acidic cation exchange resin has a large affinity for H+, it is easy to regenerate, and the exchange capacity is large (about 2 times that of the strong acid cation resin).