Weakly Acidic Cation Exchange Resins

Weakly acidic cation exchange resins are weakly acidic IERs that have carboxylic acid groups as ion-exchangable groups, as Figs 1 and 2. DIAION™ WK10, made from methacrylic acid, and DIAION™ WK40, made from acrylic acid, are in this grouping.

<Fig.1> Chemical structure of Acrylic acid type weakly acidic cation exchange resins.

<Fig.2> Chemical structure of Methacrylic acid-type weakly acidic cation exchange resins.

WK10 grades (methacrylic-type) are weak acid cation exchange resins having carboxylic acid functionalities. They have a pK value of approximately 6. WK10 has a high reaction rate, and WK11 has a high total exchange capacity. These grades are mainly used for special applications such as purification of pharmaceuticals, foods and organic chemicals. WT01S has a high reaction rate and high adsorption capacity. It is mainly used for the purification of pharmaceuticals and foods. WT01S is offered in 100-300 μm particle distribution.

WK40L is a weak acid cation exchange resin with carboxylic acid functionality based on porous acrylic polymer matrix. It has a pK value of approximately 5.3. The acrylic type WK40L resin has a higher total capacity than methacrylic type resins. It is mainly used for water treatment applications for removal of hardness ions in the presence of bicarbonate alkalinity.

Chemical Structure
Whole Bead Count 95 min.
Shipping Density
(g/L: approx.)
635 660 750 765
Salt-spliting Capacity
2.5 min 2.9 min 3.0 min 4.4 min
Water Content
53 – 59 45 – 52 45 – 55 41 – 48
Particle Size Distribution
on 1180 μm (%)
through 300 μm (%)
through 425 μm (%)
5 max.
1 max.
300 – 1060μm
85 % min.
10 % max.

3 % max.
Effective Size (mm) 0.40 min. 0.10 – 0.14 0.45 min
Uniformity Coefficient 1.6 max.
Effective pH Range 5 – 14 4 – 14
Operating Temperature (℃) 150 max. 120 max.