Weakly basic resins do not maintain their charge at a high pH because they undergo deprotonation. Strongly basic anion resins maintain their negative charge across a wide pH range, whereas weakly basic anion resins are neutralized at higher pH levels. While anion resins attract negatively charged ions, cation resins attract positively charged ions.Īnion resins may be either strongly or weakly basic. Specialised ion-exchange resins are also known such as chelating resins ( iminodiacetic acid, thiourea-based resins, and many others).Īnion resins and cation resins are the two most common resins used in the ion-exchange process. weakly basic, typically featuring primary, secondary, and/or tertiary amino groups, e.g.weakly acidic, typically featuring carboxylic acid groups,.strongly basic, typically featuring quaternary amino groups, for example, trimethylammonium groups, e.g.sodium polystyrene sulfonate or polyAMPS, strongly acidic, typically featuring sulfonic acid groups, e.g.These ion-exchange membranes, which are made of highly cross-linked ion-exchange resins that allow passage of ions, but not of water, are used for electrodialysis.įour main types of ion-exchange resins differ in their functional groups: īesides being made as bead-shaped materials, ion-exchange resins are also produced as membranes. Particle size also influences the resin parameters smaller particles have larger outer surface, but cause larger head loss in the column processes. Crosslinking decreases ion-exchange capacity of the resin and prolongs the time needed to accomplish the ion-exchange processes but improves the robustness of the resin. Additionally, in the case of polystyrene, crosslinking is introduced by copolymerisation of styrene and a few percent of divinylbenzene. ![]() The actual ion-exchanging sites are introduced after polymerisation. Most typical ion-exchange resins are based on crosslinked polystyrene.
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