Weakly acidic cation exchange resin is a resin having as an exchange group of the carboxylic acid group (-COOH) as a chemical structure below, shows the same manner weakly acidic with acetic acid and the like, or a base such as NaOH, NaHCO3 , such as You can change the salt of a weak acid.

There are two types of chemical structures, methacrylic acid and acrylic acid, and the difference is the acidity of the exchange group. For this reason, the usable pH range of methacrylic acid series is about 5 or more, and acrylic acid series is about 4 or more. Since the usable pH range is limited, its application is limited compared to strongly acidic cation exchange resins, but it has the feature that it can be easily regenerated into H easily.

The adsorption strength (selectivity) of weakly acidic cation exchange resins for various ions is roughly similar to that of strongly acidic cation exchange resins, and the higher the valence, the greater the selectivity.

Acrylic acid-based weakly acidic cation exchange resins have a slightly higher acidity and are used to treat water with high carbonate hardness. In the desalination equipment combined with strong acid cation exchange resin, it can be regenerated even with the waste liquid of strong acid cation exchange resin, thus saving regenerant. On the other hand, methacrylic acid-based weakly acidic cation exchange resins have a slightly low acidity and are rarely used for water treatment. They are used for the purification of antibiotics and amino acids.