Strong Acid Cation Exchange Resin
Strong acid cation resins (SAC) are polymer beads containing sulfonic acid groups. These groups exchange positively charged ions in water for sodium or hydrogen ions held on the resin.
In gel-type resins, water enters the crosslinked polymer structure and causes the beads to swell. Sodium and hydrogen forms represent different operating states and affect the resin treatment role.
Technical Specifications
| Polymer structure | Divinylbenzene-crosslinked gel polystyrene |
|---|---|
| Functional group | Sulfonic acid |
| Ionic form | Na⁺ |
| Total exchange capacity (Na⁺) | 1.98 eq/L |
| Moisture retention (Na⁺) | 43.6–49.7% |
| Particle size | 303–1210 µm |
| Uniformity coefficient | 1.52 |
| Specific gravity | 1.285 |
| Particle density | 1.285 g/mL |
| Shipping weight | 790–848 g/L |
Application and use
- In softeners, the sodium cycle removes calcium and magnesium; brine regeneration restores the resin for the next service cycle.
- Demineralization uses a hydrogen-cycle cation stage with downstream anion treatment, so the service form and regeneration arrangement must match.
- For industrial make-up water, assess usable cycle capacity and salt consumption together rather than sizing from total capacity alone.
Frequently asked questions
Why does conductivity stay high after softening?
Dissolved salts remain in the water after sodium-cycle softening. Check performance with a hardness measurement; conductivity alone cannot confirm softening.
Does rising pressure drop mean the resin is exhausted?
No. Retained solids or poor bed classification can restrict flow independently of ion loading. Compare the pressure trend with the backwash and pretreatment records.
Does total exchange capacity equal the amount available in each service cycle?
No. Published total capacity is a laboratory property. Usable cycle capacity depends on inlet hardness, outlet target, flow and brine-regeneration conditions.
Can this resin also serve in demineralization?
Only a grade and system suitable for hydrogen-cycle service can form the cation stage. Full demineralization also needs an appropriate anion stage.
Is every softening grade suitable for drinking or food-process water?
No. Request the exact supplied grade’s relevant approvals and conditioning instructions before selecting it for product-contact water.