Ion-Exchange Resins

Ion-Exchange Resins


synthetic macromolecular (polymeric) organic ion exchangers. According to the general classification of ion exchangers, ion-exchange resins are divided into cation-exchange resins (polyacids), anion-exchange resins (polybases), and amphoteric, or bipolar, resins (polyampholites). Cation-exchange resins may be of the strong-acid or weak-acid types; anion-exchange resins may be of the strong-base or weak-base types. If the electric charge carriers in the molecular network of an ion-exchange resin are fixed ions (functional, or ionogenic, groups) of a single type, such as sulfonic acid groups, the ion-exchange resin is called monofunctional. However, if the resin contains ionogenic groups of various types, it is called polyfunctional.

According to structural criteria, a distinction is made between microporous, or gel-like, resins and macroporous resins. The particles of gel-like resins are homogeneous. Ion exchange in a gel-like resin-solution system is possible as a result of diffusion of ions undergoing exchange through the molecular network of the swelled ion exchanger. Macroporous resins are heterogeneous; their particles have a spongelike structure—that is, they are penetrated by a system of open pores with the average diameter (200–300 to 1,000–1,200 angstroms) greatly exceeding the sizes of the solvent molecules and the ions being exchanged. The electrolyte solution freely penetrates the particles of such ion-exchange resins through the pores, which greatly facilitates ion exchange, particularly in nonaqueous systems.

Ion-exchange resins may be regarded as insoluble polyelectrolytes.

Table 1. Properties of some Soviet industrial ion-exchange resins
Expressed in terms of the number of milliequivalents of ions absorbed by 1 g of dry resin upon contact with standard solution of sodium hydroxide (for cation-exchange resins)
 Static exchange capacity1(meq/g)Specific volume2(ml/g)Maximum use temperature (°C)Basic raw material
Strong-acid cation-exchange resins
KU-1 ................4.2-4.5 2.6-3.0 80 phenol, formaldehyde
KU-2 ................4.8-5.2 2.5-2.9 130 styrene, divinylbenzene
Weak-acid cation-exchange resins
KB-2 ................10-11 2.6-3.0 100 acrylic acid, divinylbenzene
KB-4 ................85-10 26-30 100 methacrylic acid divinylbenzene
Strong-base anion-exchange resins
AV-16 ................8.0-9.5 3.6-4.2 90 polyamines, epichlorohydrin, pyridine
AV-17 ................3.5-4.2 2.5-3.0 50 styrene, divinylbenzene
Weak-base anion-exchange resins
AN-2F ................85-10 25-32 50 polyamines phenol
AN-18 ................3 5-5.0 20-25 60 styrene divinylbenzene
EDE-10P ................8.5-9.5 2.6-3.2 45 polyamines, epichlorohydrin

The multicharged ion, which forms the structural network of the ion-exchange resin, is virtually immobile because of its high molecular weight. This ion network, or ion grid, binds small, mobile ions of opposite sign (counterions), which are capable of equilibrium exchange for ions from the surrounding solution. The properties of some industrial brands of Soviet ion-exchange resins are listed in Table 1. The average particle size of such ion-exchange resins is 0.2–2.0 mm, and the corresponding bulk densities are 0.5–0.9 ton/m3.

Ion-exchange resins are produced by polymerization, poly-condensation, or polymer-analogous transformations (so-called chemical treatment of polymers that initially did not have ion-exchange properties). Ion-exchange resins derived from styrene-divinylbenzene copolymers have become widely used in industry. These resins include strong-acid cation exchangers, as well as strong- and weak-base anion exchangers. The basic raw materials for the industrial synthesis of weak-acid cation exchangers are acrylic and methacrylic acids and the corresponding esters. Ion-exchange resins based on phenol-aldehyde polymers and polyamines are also manufactured in large quantities. Controlled synthesis of ion-exchange resins results in materials with the desired engineering characteristics.

Ion-exchange resins are used for desalinization of water, extraction and separation of rare elements, and purification of the products of the organic and inorganic synthesis.


References in periodicals archive ?
Request TOC of this Report- Sulfonic acid and the conventional ion-exchange resins are extensively used in several industrial applications such as recovery and creation of metals, industrial wastewater treatment.
The transaction includes Studsvik's Tennessee processing plants located in Erwin and Memphis, patents to its THOR technology in China as well as its stake in their Semprasafe LLC joint venture that processes ion-exchange resins.
Holl, "Sorption of heavy metals onto selective ion-exchange resins with aminophosphonate functional groups" Industrial and Engineering Chemistry Research, vol.
We were the first received and investigated new phosphate cation-exchange resins, nitrogen-phosphorus containing ion-exchange resins using chemical transformation of benzyl bromide-furfural polymers (Tursunov and Nazirova, 1985b; 1985c).
Onectra Inventors has applied for a patent for encapsulating radioactive waste, particularly ion-exchange resins. Virginie Lalia and Bernard Rottner are listed as inventors on the project.
In the study, the researchers created an adsorbent material that - unlike conventional ion-exchange resins that are frequently used in reactors - is selective for cobalt but has the unique ability of disregarding iron-based ions.
The most common method for removal of perchlorate from drinking water is to use ion-exchange resins, which pull out the pollutant but don't destroy it.
ban on trade with Cuba involving sales from 1992 to 2000 of about $2 million worth of ion-exchange resins used in water purification.
The water delivered by the first system was purified using a DI cartridge (5 L of mixed-bed ion-exchange resins, with the resins being regenerated when the water resistivity-drops to less than 1 M[omega].cm).
Behavior of carbohydrates toward strongly basic ion-exchange resins. Arch.