Ion-Exchange Polishing
Mixed-Bed Cation/Anion Polishing Column
The mixed-bed cation/anion polishing column is a 4-kilogram, 316L stainless steel cartridge that polishes reverse-osmosis permeate into electronics-grade water exceeding 15 megohm-centimeters of resistivity at a throughput of 5 liters per hour. Operating with zero power consumption, the bed uses strong-acid cation and strong-base anion resins with an exchange capacity of 1 to 2 equivalents per liter to replace dissolved ions with hydrogen and hydroxide ions. In the lunar environment, the limited radiation tolerance of organic resins causes progressive media degradation, requiring periodic cartridge replacement every 18 months when effluent conductivity monitors detect performance loss.
Mixed-bed ion-exchange column polishing RO permeate to electronics-grade purity (>15 MOhm cm).
Purpose
Mixed-bed ion-exchange column polishing RO permeate to electronics-grade purity (>15 MOhm cm).
Context
Child of L2-WTR-PURE in L1-WTR water processing chain
Principles
- ▸Strong-acid cation + strong-base anion resins exchange H+/OH- for dissolved ions
- ▸Mixed-bed achieves higher purity than separate beds
- ▸Resin capacity 1-2 eq/L; replaceable cartridge
- ▸Effluent conductivity monitor triggers replacement
- ▸Continuous-flow with gradual breakthrough
Typical implementations
- ▸Industrial DI water systems (Veolia, Suez)
- ▸Semiconductor-grade water purification
- ▸ISS WPA polishing column
Lunar considerations
- ▸Cartridge replacement via L1-MNT every 1-2 years
- ▸Resin radiation tolerance limited — periodic refresh prevents performance loss
- ▸Spent cartridges to L1-WMS for end-of-life processing
Specifications
Functional
| primary function | Mixed-bed ion-exchange column polishing RO permeate to electronics-grade purity (>15 MOhm cm). |
| output resistivity mohm cm | 15 |
| throughput lph | 5 |
| cartridge months | 18 |
Physical
| mass kg | 4 |
| materials | Strong-acid cation resin, Strong-base anion resin, 316L SS column |
| vacuum compatibility | True |
Operational
| power consumption w | 0 |
| thermal range c | -40, 70 |
| lifetime years | 15 |
| mtbf hours | 100000 |
Interfaces
Provides
- Ultra-pure water to distribution
- Make-up water for RFC closed loop
Requires
- Sterilized water
- Cartridge replacement
Cite this entry
Lunar Ark Codex. "Ion-Exchange Polishing" (L3-WTR-PURE-ION). Retrieved 10 September 2026, from https://lunarark.com/entry/L3-WTR-PURE-ION
Licensed CC-BY-SA 4.0. You may reuse and adapt this entry with attribution, under the same licence.