Ion exchange resins

Ion exchange resins:

Ion exchange resins are porous polymers that have a gel macro- or macroporous structure of different densities. On the surface of the pores are covalently bound ionic groups with exchanging ions fixed on the surface.It acts as an water filter for home

Granules usually have the correct spherical shape when obtained by polymerization, and the irregular shape if obtained by polycondensation. The size of the granules, depending on the functional needs, can range from 10-20 microns to several millimeters.

Roughly speaking, they consist of a framework – a matrix and functional groups (fixed ions) that are rigidly fixed to the matrix and interact with counterions.

Resins are divided into three main types: cation exchangers and anion exchangers.

Cationites – counterions are cations (have a positive charge, for example, H + , Na + );

Strongly acid cation exchangers — have a sulfo group —SO 3 and a phosphorus group —RO 3 as functional groups . Spherical granules with a yellow or amber hue are characteristic. The most common cation exchangers. Have high exchange capacity, high osmotic resistance (up to 120 of C) operate at any level of pH. In most cases, they are used to soften water and are supplied in sodium form, due to which they are well regenerated by sodium chloride or edible salt.It has similar features as of water filter for home.

If we talk about the market, it is worth mentioning such popular resins DOWEX Marathon C (exchange capacity – 2000 mEq / L), Dowex HCR-S / S (1900 mg / eq-L). Ecosoft company produces high-quality Ukrainian analogue of Ecolite CK (1800 mEq / l).

Weakly acid cation exchangers contain, as functional carboxyl groups, COO, OH. They are painted slightly green or white. They are well restored by perchloric acid and are also popular as a component of mixtures.

– anion exchangers – the anion (OH – , Cl – ) plays the role of the counterion . They are used mainly in industrial processes, since they work only in an alkaline environment.

Strongly basic anion exchangers have a quaternary ammonium group as functional. Characteristic yellow or light yellow color. They are often used to separate metal ions at any pH. Used to remove various anions, including bicarbonates, sulfates, etc.

Weakly basic (low basic) anion exchangers have amino groups of varying degrees of substitution as functional groups: – NH 2 + , = NH + . They have a narrow application, mainly in chromatographic analysis. Work only in an acidic environment.

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