Find out which ResinTech products are suited for radium removal by application.
ResinTech CG8
ResinTech CG8 can be used to remove radium from water. Radium has a selectivity coefficient of about 40:1 compared to sodium. This is 8.3 times as high as calcium which is only 5:1. On a single use the cation resin will load radium 8.3 times beyond the hardness endpoint. For example, if a resin lasts 1,000 gallons per cubic foot before hardness starts to break through, then it will last 8,300 gallons before radium starts to breakthrough providing it is only used once. Because of its very high selectivity, radium is very difficult to remove from the resin. Radium has slow kinetics and is usually loaded at trace quantities which makes regeneration even harder.
Sodium Cycle Operation
Termination of the run at the hardness breakthrough - Radium leakages remain consistently low when the cation resins are run only to hardness breakthrough. It is advisable to use regeneration contact times of one hour, regenerant levels of 15 lbs. per cubic foot and salt concentrations of at least 10% at the resin bed.
Termination of the run at radium breakthrough - After a few cycles, this will give only about 5 to 10% more gallonage than hardness break. A normal regeneration level such as 15 to 20 lbs. of sodium chloride per cubic foot at 10 to 15% concentration is not enough to remove all of the radium, so radium will be building up on the resin bed. When the hardness breaks it will push some of the remaining radium off at the bottom of the bed so the radium breaks just after hardness. The minimum recommended salt dosage is 15 lbs. per cubic foot at a minimum concentration of 10%.
Calcium Cycle Operation
The unit is run with the resin in calcium form. This method leaves the hardness intact and only removes the radium. Because of the high affinity of radium over calcium, it is feasible to remove only radium and leave the hardness intact.
Radium and calcium are both divalent, so concentration itself does not play as important a role as in hardness versus sodium exchange. Nevertheless, there is a drop in activity of the radium ion in solutions at the higher salt concentrations, so a more concentrated salt produces better results. Calcium chloride salt is used as the regenerant. It is recommended that concentrations of at least 10% CaCl2 be maintained during regeneration.
High initial radium leakages will always be present during co-current regeneration unless the resin is mixed after regeneration. Calcium is unable to push off all the radium from the bed. However, it is more effective than sodium and pushes the radium to the bottom of the bed.
During the subsequent cycle, calcium ions not removed from solution act as a continual mild regenerant and will push off some of the radium remaining at the bottom of the bed, especially at breakthrough. Mixing the bed after regeneration provides a uniform concentration of radium throughout the bed which gives consistent and lower leakage. Another way to use the calcium process effectively is to use counter-current regeneration (CCR). This way the radium is pushed away from the bottom of the bed so that the radium band is moved up into the bed thus avoiding the problem of high initial leakage. Obviously no mixing can be used with CCR.
ResinTech RSM-25
Specialized, higher crosslinked resins such as ResinTech RSM-25 work well for one time use on all waters. A 15% crosslinked macroporous resin has about two times the selectivity that an 8% resin has for radium over calcium.
It is estimated to have 15 times the selectivity for radium as for hardness so it would give 15 times the throughput capacity to a radium break than to a hardness break. This resin is ideal for point-of-use (POU) and single use applications regardless of sulfate concentration in the water.
RSM-50-HP Hybrid Cation Exchanger
This media is the result of monoatomically dispersing barium sulfate into a highly crosslinked macroporous strong acid cation. The media that has exceptionally long throughput capacity for single use radium removal. Because of the high radium removal capacity this media is typically run to a TENORM* endpoint for disposal consideration.
The potential for barium to leach out of the resin at levels above the maximum contaminant level (MCL) of 2 mg/L exist when the feed water has low sulfate concentrations.
Summary
ResinTech RSM-50-HP offers the highest capacity and is the recommended product for applications that either have high hardness or can not use a salt regenerable product. The feed water must contain a sufficient sulfate concentration for successful operation. This product will
give the highest radium removal throughput.
ResinTech RSM-25 is the recommended product for applications that have high hardness and low sulfate concentrations. This resin will give 15 times the throughput capacity to a radium break than a hardness break.
ResinTech CG8 is recommended for salt regenerable applications and requires higher salt doses during regeneration to remove radium from the resin bed.
The selection of the proper cation exchange resin as well as the method of operation is highly dependent on the inlet water analysis. It is imperative to obtain a complete water analysis** before proceeding with system design. These are the inlet water parameters required:
• pH
• TDS or Conductivity
• Calcium
• Magnesium
• Sodium
• Iron
• Manganese
• Sulfate
• Nitrate
• Chloride
• Alkalinity
* Technologically Enhanced Naturally Occurring Radioactive Material (TENORM) is defined as, “Naturally occurring radioactive materials that have been concentrated or exposed to the accessible environment as a result of human activities such as manufacturing, mineral extraction, or water processing.” – US EPA
** ResinTech recommends the Basic Well Water Test Kit:
https://www.resintech.com/product/basic-well-water-test-only/