Ion Exchange Resins

Ion Exchange Resins Overview

• Urbans Aqua stocks Purolite, Thermax and ResinTech ion exchange resins for softening, tannin reduction and PEDI applications.
• There are hundreds of ion exchange resins. We divide them into three categories – Cation, Anion and Mixed Bed.

In Stock Brands:

Visit our PDF Library for technical specifications and product manuals on cation resins.

Visit our SDS Library for safety data sheets on cation resins.

Link to WQA Gold Seal Purolite Resins

Link to WQA Gold Seal Thermax Products

Urbans Aqua Ion Exchange Resins

Cation Resin

Cation ion exchange resins may be light or dark in color.  Color variation in new cation has no impact on its performance. For drinking water applications look for WQA Gold Seal.

Cation resins by type are:

• Strong Acid Cation (SAC) resin are sulfonated copolymers of styrene and DVB.
• Weak Acid Cations (WAC) have a polyacrylic backbone.
• SAC and WAC resins are manufactured in different forms – macroporous and porous (gel).

Cation resins in the Na+ form will exchange sodium for the following ions:

• Calcium (Ca++)
• Magnesium (Mg++)
• Iron (Fe++)
• Manganese (Mn++)

In the H+ cation resin will exchange hydrogen for the following ions:

• Calcium (Ca++)
• Magnesium (Mg++)
• Manganese (Mn++)
• Iron (Fe++)
• Sodium (Na+)

Strong Acid Cation

Gel type cation resin consists of clear or translucent beads, and is commonly used in standard applications such as softening. It has greater capacity and regeneration efficiency than macroporous cation. Gel type cation resin is often referred to by its cross-linkage percentage.

• Higher cross-linked cation exchange resins can withstand more aggressive circumstances – e.g. higher chlorine levels.
• Resins with cross linkage of 6% are commonly used for well water applications.
• Municipal water has a chlorine residual so 8% cross-linked resins, such as Purolite C-100Na or Thermax T42Na, are recommended.
• 10% cross-linked resins (Purolite C-100×10 Na or Thermax T-52Na) are often installed in commercial industrial applications or where the chlorine or chloramine content is higher than what is recommended by resin manufacturers. See pdf –  Chlorine Limitations

Macroporous cation beads are opaque. It’s commonly used in aggressive softening applications.

• High temperatures where oxidants such as chlorine are also present.
• Although the capacity is lower than gel, macroporous will last longer.
• Macroporous resin has larger pore sizes than gel resin and can be cross-linked by as much as 20%.

Weak Acid Cation

Although weak acid cation resin softens water it is never used in residential applications.

• WAC resin is in the hydrogen form (H+).
• If used in a household setting the pH of the water passing through the system is greatly reduced.
• WAC is commonly used to remove alkalinity, to soften water containing high salinity and for removal of heavy metals.

Cation Exchange Process

Softening

Softening with cation resin is a simple exchange function.

• The resin bead is negatively charged and attracts positive ions.
• When supplied in the sodium form (Na+) the resin will exchange sodium ions for hardness ions – calcium and magnesium.
• The bead is more strongly attracted to these ions and readily exchanges with the sodium.
• Once the resin is exhausted it is regenerated with a brine solution (NaCl).
• The brine overwhelms and releases the calcium and magnesium from the bead.
• The resin is “converted” back to the sodium form and ready for re-use.

Iron Reduction

Other positively charged metals such as ferrous iron and lead are also attracted to the cation resin and will be removed. These metals are not easily regenerated off and will reduce the softening capacity and life of the resin.

Demineralization

SAC in the hydrogen form (H+) in combination with strong base anion (SBA) in the hydroxide form (OH), is most often used for demineralization processes such as portable exchange tank (PEDI) operations. Hydrogen, not sodium, is exchanged for calcium, magnesium and sodium. (For more information please refer to section on demineralization for portable DI exchange operations.)

Anion Resin

Anion exchange resins are usually light in color.  Color variation in new anion has no impact on its performance. For drinking water applications look for WQA Gold Seal certfied products.

Visit our PDF Library for technical specifications and product manuals on anion resins.

Visit our SDS Library for safety data sheets on anion resins.

The most popular anion resins by type are:

• Type 1

  • Type 1 anions (SBA-1) have the strongest affinity for weak acids but lower regeneration efficiency which equates to lower capacity.
  • SBA Type 1 macroporous anions are often used for organics or tannin reduction.
  • Regeneration is with brine making it suitable for residential purposes.
  • Nitrate selective SBA Type 1 macroporous anions are also available for nitrate reduction of potable water. (SBA-2 also removes nitrate but is not selective. It is commonly used where equipment operators are present.)
  • Higher regeneration efficiency is attained by increasing regenerant temperature for SBA-1.

• Type 2

  • Type 2 anions (SBA-2) have less affinity but are strong enough to remove weak acids for most applications. SBA-2 resin has considerably greater regeneration efficiency thus higher capacity.
  • SBA-2 lacks the chemical stability of SBA-1 resins and cannot withstand high temperatures. It will significantly reduce its capacity.
  • SBA-2 resins are commonly used for dealkalization purposes.
    • Using salt alone is often satisfactory but in combination with caustic soda there is a greater reduction in alkalinity leakage and carbon dioxide. (When using the brine/caustic combination it is necessary to pre-soften to avoid precipitation of calcium and magnesium compounds.)

• Weak Base Anion

  • Weak base anions are used for reduction of organic acids and other organic materials. There are 2 types, gel and macroporous.
  • “Weak base resins do not contain exchangeable ionic sites and function as acid adsorbers. This is why the active form is referred to as the free base form. These resins are capable of sorbing strong acids with a high capacity and are readily regenerated with caustic. They are therefore particularly effective when used in combination with a strong base anion by providing an overall high operating capacity and regeneration efficiency.” Dupont Ion Exchange Resins- Chemical Structure Anion Exchange Resins

Anion resin in the Cl- will exchange chloride for the following:

• Sulfates (SO4- -)
• Nitrates (NO3- -)
• Alkalinity (H2CO3)
• Carbonates (CO3- -)

In the OH form anion resin will exchange hydroxide for the following:

• Chloride (Cl-)
• Sulfates (SO4- -)
• Nitrates (NO3- -)
• Alkalinity (H2CO3)
• Silica (SiO2-)
• Carbon Dioxide (CO2)

 Mixed Bed Ion Exchange Resins – Cation (H)/Anion(OH)

Visit our PDF Library for technical specifications and product manuals on mixed bed resins.

Visit our SDS Library for safety data sheets on mixed bed resins.

Deionization or Demineralized Water Applications

Highly unlikely to be used by a home owner due to its aggressive nature, deionized water is commonly used in

• Pharmacies
• Laboratories
• Spot Free Rinse
• Kidney dialysis
• Power plants
• Humidification
• Any applications requiring ultrapure or low TDS water

PEDI or SDI Business – DI Exchange Tanks

The founders of Urbans Aqua have extensive experience having owned and operated the second largest DI business in the Mid-Atlantic region of the US.  We are delighted to share our knowledge with dealers who want to grow or need technical assistance with their DI businesses.

Some tips:

• In demineralizer or deionizer applications, the cation (H+) and anion (OH) resins tanks are referred to as separate beds. Tanks containing mixed bed ion exchange resin are polishers.  Polishing tanks are often placed after RO systems to provide higher quality water.
• The quality of regenerant used may affect regeneration quality. Follow resin manufacturer recommendations for further information.
  • Cation ion exchange resins can be regenerated using sulfuric or hydrochloric (muriatic) acid. Regeneration procedures are different.
  • Anion resin is regenerated with membrane grade caustic.
• As resin exhausts its volume is reduced.  Anion volume may be reduced by 12-15%; cation by 4-6%.
  • It’s strongly recommended to buy anion in the exhausted chloride form given the swell factor.  When in the chloride form there are 12-15% more beads per cubic foot.  The anion resin will need to be double regenerated prior to use.  
  • However, we advise buying the cation in the regenerated hydrogen form.
• For SDI (portable exchange tank) applications, we recommend using ion exchange resin components which vary in color.  The color difference helps distinguish effectiveness of separation.
  • Black Cation and Gold Anion
  • Gold Cation and White Anion, is less desirable.
•  Conventional resin bead size doesn’t vary widely. UPC (uniform particle size) ion exchange resins are recommended for SDI.  The separation of the mixed bed resin will be more clearly defined and result in a smaller heel. (The heel is the mixture of cation and anion beads at the point of separation.)
•  Mixed Bed is typically supplied as 50-50 chemical equivalence.  There is no one size fits all application.  The ratio of cation to anion can be changed depending on the chemistry of the water or the customer’s process.
  • The capacity of the cation resin is greater than the anion.  Furthermore, the cation regeneration process is far more effective than the anion regeneration process. For this reason, many PEDI/SDI companies will provide their customers with appropriately sized vessels.  Typically, a larger anion tank where there are separate beds or a mixed bed with an adjusted 1:1.5 ratio of cation to anion resin.

If you are a water treatment dealer, plumber or well driller and have questions regarding this post contact Michael Urbans @ 610-365-7818. Contact Us

Urbans Aqua is a stocking wholesaler of Residential & Commercial Water Treatment Equipment and Supplies including Purolite , Thermax and ResinTech Ion Exchange Resin; Calgon & Jacobi Activated Carbon; Filterag Plus; GreensandPlus; Pyrolox Advantage; KDF; Birm; Sand/Gravel; Clack, Fleck, Autotrol & AqMatic valves; Stenner Pumps & Parts. 

Urbans Aqua sells exclusively to water treatment professionals.  We do not deal with the general public.