Resins for Water Treatment
The treatment of water uses a wide range of resins which are used for multiple applications such as the removal of total dissolved solids (TDS) and hardness ions (Ca, Mg). The main two general types of ion exchange resins are as below:
Cation Resin: a resin exchanges positive (+) ions such as sodium and calcium which has a base-resin with a negative charge.
Anion Resin: a resin exchanges negative (-) ions such as chloride and sulfate which has a base-resin with a positive charge.
Ion Exchange Resins Chemistry
Ion exchange resins are manufactured by cross-linking of hydrocarbon chains through a polymerization process. The cross-linking structure gives resins strength and resistance properties. The main chemical structure of resins is polystyrene but there are other structures that can be used such as acrylic-based polymers. These polymeric resins are then modified with chemical functional groups with a specific charge. These functional groups and charges are the main factors differentiating the applications of ion exchange resins. These are the main classifications of resins:
- Strong Acid Cation (SAC) Resins: these resins are manufactured of polystyrene structure with a strong functional group of sulphonate (R-SO3–) that is either charged with sodium ions (Na2+) for softening applications, or hydrogen ions (H+) for water demineralization.
- Weak Acid Cation (WAC) Resins: these resins are manufactured of acrylic-based polymer that was hydrolyzed with either sulphuric acid or caustic soda to produce carboxylic acid functional groups (R-COO–). Due to their high affinity for hydrogen ions (H+), WAC resins are typically used to selectively remove cations associated with alkalinity.
- Strong Base Anion (SBA) Resins: these resins are typically manufactured of polystyrene structure that has undergone chloromethylation and amination to attach anions to exchange sites. Type-1 SBA resins are produced by the application of triethylamine (TMA), which yields chloride ions (Cl–), while Type-2 SBA resins are produced by the application of dimethylethanolamine (DMEA), which yields hydroxide ions (OH–).
- Weak Base Anion (WBA) Resins: these resins are typically manufactured of polystyrene that was undergone chloromethylation, followed by amination with dimethylamine. WBA resins are unique in that they do not possess exchangeable ions, and are therefore used as acid absorbers to remove anions associated with strong mineral acids.
- Chelating resins: these resins are the most common type of special application resins which are used for selective removal of specific metals and other substances. Commonly the resin structure is composed of polystyrene, though a variety of substances are used for the functional groups, including thiol, triethylammonium, amino-phosphonic, and many others.
REDA Water has agreements with main global manufacturers of Resins especially with LANXESS in many countries in the MENA region. Don’t hesitate to Contact Us for any inquiry.
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