Mixed-Bed Resins
Mixed-bed resins combine cation and anion exchange beads in a single bed for high-purity water preparation. Water passing through the mixture undergoes both types of ion exchange.
For demineralization, the cation component is used in hydrogen form and the anion component in hydroxide form. These released ions combine to form water.
Technical Specifications
| Polymer structure | Divinylbenzene-crosslinked gel polystyrene |
|---|---|
| Functional group | Sulfonic acid + Type I quaternary ammonium |
| Ionic form | Cation H⁺ / anion OH⁻ |
| Appearance | Spherical beads |
| Cation / anion ratio (by volume) | 42.5% / 57.5% |
| Particle size | 300–1200 µm |
| Particles below 300 µm | 1% |
| Uniformity coefficient | 1.65 |
| Shipping weight | 705–740 g/L |
Application and use
- After primary demineralization, a mixed bed polishes residual ions; outlet quality must be monitored against the process requirement.
- Replaceable cartridges provide a service option where on-site chemical regeneration is unavailable; replacement is tied to measured outlet quality.
- In regenerable vessels, the resin components must separate for regeneration and then remix correctly before returning to service.
Frequently asked questions
Does high resistivity prove that organic contamination is also low?
No. Resistivity describes ionic purity. Confirm TOC separately when the process has an organic contamination limit.
Why can a newly loaded bed miss its initial rinse target?
Resin clumping can impair initial performance. Check the commissioning procedure and rinse results before treating a slow start-up as permanent resin failure.
Can the mixed bed replace upstream demineralization?
Its suitability and run length depend on inlet ionic load and the outlet target. Provide the upstream treatment and water analysis before selecting a stand-alone or polishing duty.
Can a cartridge blend be regenerated in the existing vessel?
Only if both blend and vessel are designed for component separation, separate regeneration and remixing. Non-regenerable cartridges are replaced.
Does a 40:60 blend equal a product described as 1:1?
Not necessarily. A 40:60 volume ratio and a 1:1 chemical-equivalent ratio use different bases. Compare the components and stated ratio basis.