Demand High-Purity Water

Water softening, purification, separation and pretreatment can all benefit from the use of IX to protect downstream equipment and increase operational efficiency.

Ion exchange (IX) systems are used in a variety of industries for water softening, filtration and separation. Ion exchange (IX) is a process in which dissolved ions are exchanged for more desirable ions with a similar electrical charge. While the chemistry of individual ion-exchange reactions varies depending on the application, IX is a process in which dissolved ions are exchanged for more desirable ions with a similar electrical charge.

IX systems, which use a physical-chemical process to swap out unwanted ions for ions with the same electrical charge, remove ionic pollutants from solutions. This reaction occurs when a process or waste stream passes through a resin capable of ion exchange in an IX column or tank. For example, a water softening IX system is designed to eliminate scale-forming calcium or magnesium ions from the solution. Calcium and magnesium ions are efficiently collected and retained by an IX resin composed of concentrated sodium ions, while sodium ions are discharged into the effluent stream.

A well-designed IX system meets the requirements of a specific application in terms of both physical design criteria and the IX resin material used. A standard IX vessel contains IX resin, an input distribution system, a regenerant distribution system, retention elements, a PLC, control valves, and pipes. The resins are the most important component of an IX system. The feed stream components, as well as other process variables, will influence the geometric shape, size, and material used in the IX resin.

Ions are charged atoms or molecules that can be positively or negatively charged. Anions (negatively charged particles) and cations (positively charged particles) are formed when an ionic substance dissolves in water (negatively charged particles). To replace ionic molecules selectively based on their electrical charges, IX makes use of this capability. It is necessary to introduce an ionic solution into an IX resin matrix in order to begin the ion exchange reaction.

IX resins are available in a variety of forms, including small porous microbeads and a sheet-like membrane. IX resins are made up of a hydrocarbon network that electrostatically binds a large number of ionizable groups. Organic polymers, such as polystyrene, are used to make them. As the process or waste stream passes through the IX resin, the loosely held ions on the surface are replaced by ions that have a stronger affinity for the resin component.

After a period of time, the resin becomes saturated with contaminating ions and must be recharged or regenerated. This is accomplished by flushing the resin with a regenerant solution. By substituting cations or anions on the resin surface and releasing polluting ions into the wastewater, the regenerant, which is typically a strong salt, acid, or caustic solution, reverses the IX reaction.

The most common application of IX is sodium zeolite softening, but other important applications include high-purity water generation, dealkalization, and metals removal. Despite the fact that IX resins must be carefully selected based on the chemicals in the feed stream, it can be a very effective method for removing dissolved pollutants.

Cationic Resins

Both strong acid cation (SAC) and weak acid cation (WAC) resins are widely used for demineralization. SAC resins are frequently used in softening applications, whereas WAC resins are frequently used in dekalification applications. Frequently, cation resins are used to remove the following contaminants:

  • Calcium (Ca2+)
  • Chromium (Cr3+ and Cr6+)
  • Iron (Fe3+)
  • Magnesium (Mg2+)
  • Manganese (Mn2+)
  • Radium (Ra2+)
  • Sodium (Na+)
  • Strontium (Sr2+)

Anionic Resins

There are two types of anion exchangers: strong base anion (SBA) resins and weak base anion (WBA) resins. Acid absorption resins such as WBA are frequently used, whereas demineralization resins such as SBA are frequently used. Frequently, anion resins remove the following contaminants:

  • Arsenic
  • Carbonates (CO3)
  • Chlorides (Cl–)
  • Cyanide (CN–)
  • Fluoride
  • Nitrates (NO3)
  • Perchlorate (ClO4-)
  • Perfluorooctane sulfonate anion (PFOS)
  • Perfluorooctanoic acid (PFOA)
  • Silica (SiO2)
  • Sulfates (SO4)
  • Uranium

Specialty Resins

While specialty IX resins have proven to be effective in a variety of industrial applications, their greater specificity comes at a higher cost and with a narrower application than standard IX resins. Chelating resins are commonly used to concentrate and remove metals like cobalt (Co2+) and mercury (Hg and Hg2+) from dilute solutions. Meanwhile, natural organic materials are frequently removed from feed water using magnetic ion exchange (MIEX) resins.