ION EXCHANGE RESIN
Ion Exchange (IX) is an incredibly versatile technology often utilized in industrial water treatment and selective separation. While all resins generally function on the same basic principles, there is a seemingly endless variety of IX resins available on the market today. Once you understand the basic resin types and their functions, it might be easier to narrow down the right types for your industrial facility and see how they can potentially help to improve your process.
WHAT ARE ION EXCHANGE RESINS?
IX resins are materials that facilitate IX reactions. They are composed of polymer matrices to which ionic “functional groups” of either positively-charged ions (cations) or negatively-charged ions (anions) are permanently bound. Some specialty resins have both types of functionality. These functional groups have a net negative or positive charge that allows them to readily attract counter ions, or ions of an opposing charge. As a liquid stream flows through the IX resin, the counter ions can be replaced by ions of a similar charge.
APPLICATION
- Water Treatment
- Food & Beverage
- Pharmaceutical & Bio Industry
- Chemical Processing
- Electronics Industry
- Metal Industry
- Energy
- Household / Sanitary
Broadly speaking, resins are named for the type of ions they exchange, meaning that cationic resins exchange positively charged ions, while anionic resins exchange negatively charged ions and include:
VARIANT
Strong Acid Cation Resins
Weak Acid Cation Resins
Strong Base Anion Resins
Weak Base Anion Resins
Specialty
Resins
Strong Acid Cation Resins
What they are
Strong acid cation (SAC) exchange resins are among the most widely used resins. They are composed of a polymer matrix to which anionic functional groups are bound, such as sulphonate (SO3–). SAC resins are regenerated with either a sodium salt solution (Na2+) for softening applications, or with an acid (H+) for demineralization applications.
What they’re used for
SAC resins are used extensively for softening applications, and are very effective at complete removal of hardness ions such as magnesium (Mg+) or calcium (Ca2+). They may also be used in split-stream dealkalization, where two SAC beds operate in parallel, the first as a softener that produces an alkaline solution, and the second as a demineralizer (in the H+ form), with the result that alkalinity is removed from the blended stream. Certain varieties of SAC resins have also been developed for applications demanding removal of barium and radium from drinking water or other streams. SAC resins can be damaged by oxidants and fouled by iron or manganese, so care must be taken to avoid exposure of the resin to these materials.
Weak Acid Cation Resins
What they are
Weak acid cation (WAC) exchange resins remove cations associated with alkalinity (temporary hardness). WAC resins typically employ carboxylic acid functional groups (RCOO–), and are regenerated with sulphuric or hydrochloric acid. Similar to SAC resins, WAC resins swap cations for hydrogen ions, resulting in slightly greater acidity in the treated stream.
What they’re used for
WAC resins are used for demineralization and dealkalization applications. Their high affinity for divalent cations ions (Ca2+ and Mg2+) makes them a good choice for applications demanding the removal of hardness ions associated with alkalinity. For high temporary hardness applications, a WAC resin can be used ahead of a SAC resin in a two-step IX process. Additionally, WAC resins tend to have relatively high oxidation resistance and mechanical durability, making them a good choice for streams containing oxidants such as hydrogen peroxide and chlorine, among others.
Strong Base Anion Resins
What they are
Strong base anion (SBA) exchange resins are available in multiple varieties, including Type 1, Type 2, and acrylic or macroporous. Each type of SBA resin offers a unique set of benefits and constraints that must be matched to the application at hand.
What they’re used for
SBA resins are typically used for demineralization, dealkalization and desilication, as well as removal of total organic carbon (TOC) or other organics depending on the type of resin. Type 1 SBA resins are used for selective removal of nitrates (NO3-), sulphates (SO3-), and perchlorate (ClO4-), for general demineralization, and for desilication where low levels of silica are required. Type 2 SBA resins are used for applications where total removal of anions is desired, where lower use of caustic is preferred, and where low silica levels are not critical to operational processes.
Weak Base Anion Exchange Resins
What they are
Weak base anion (WBA) exchange resins are the only major type of IX resins that do not have exchangeable ions. These resins adsorb free mineral acidity (Cl and SO4). WBA resins have amine functional groups, and are typically regenerated with sodium hydroxide (NaOH), ammonia (NH3), or sodium carbonate (Na2CO3).
What they’re used for
WBA resins are used for partial demineralization. In larger plants, WBA resin beds may be paired with SBA units for complete demineralization applications, and WBA resins are also effective as total organic carbon (TOC) barriers ahead of SBA beds. WBA is also used for acid adsorption applications involving the removal of chloride, sulphate, nitrate, and other anions associated with strong acids, though it is not effective for removal of weak acids such as silica (SiO2) and carbon dioxide (CO2).
Specialty Resins
What they are
As their name implies, specialty resins are used for a variety of specific applications. Chelating resins are the most common type of specialty resin, and are used for selective removal of certain metals, brine softening and other substances. Specialty resin functional groups vary widely depending upon the application at hand, and may include thiol, iminodiacetic acid, or aminophosphonic acid, and others.
What they’re used for
Chelating resins are used extensively for concentration and removal of metals in dilute solutions, such as Cobalt (Co2+) and Mercury (Hg2+). Another type of specialty resins are magnetic ion exchange (MIEX) resins, which used for removal of natural organic matter from liquid streams.
PT. Hydromart Utama Indonesia has more than 15 years experience in identifying appropriate IX resin technologies to help lower costs and waste volumes while increasing product quality. For more information or to get in touch, contact us here to set up a consultation with an engineer or request a quote.
We can walk you through the steps for developing the proper solution and realistic cost for your IX treatment system needs.
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