Process Diagram Demonstration

Ion Exchange Resin is a polymer compound containing a functional group (active group having exchangeable ions), with a network structure and insolubility property. In general, it is presented as spherical particles.

Ion Exchange Resin is named after different matrix categories, physical structures and acid-base properties.

Based on different pore structures, resin is divided into 2 types: Gel Type and Macropore Type. As for the resin that has a pore structure, ‘macropore’ is prefixed for nomination.

When it comes to the classification of acidity and alkalinity, prefix ‘cation’ ahead of acidic resin while ‘anion’ prior to alkaline resin. For example, ‘Macroporous Strongly Acidic Styrene-based Cation Exchange Resin’.

In addition, based on diverse matrix substrate, ion exchange resin can also be classified as Styrene-based Resin and Acrylic-based Resin.

The type of chemically active functional groups determines the major properties and classes. First of all, resin is divided into 2 main categories: Cationic Resin and Anionic Resin, which can exchange cations and anions in solution. Moreover, cationic resins are generally classified into strongly acidic and weakly acidic while anionic resins are divided into strongly basic and weakly basic. Furthermore, medium-strong acidic and medium-strong alkaline.

Strongly Acidic Cation Exchange Resin

This resin contains a large amount of strongly acidic groups, such as

sulfonic acid group: -HSO3 , which readily dissociates H+ ions in solutions and therefore presents strongly acidic. Meanwhile, after the resin is dissociated, the negatively charged groups contained in the matrix, such as -SO3, can adsorb and combine other cations within the solution. These two reactions are how H+ ions in the resin exchange with other cations in the solution. Strongly acidic resins have strong electrolysis ability and can dissociate and exchange ions both in acidic and alkaline solutions.

Resins are required to be regenerated after being used once, when ion exchange resin beads are exhausted (fully loaded), the process in which ion exchange reaction is carried out in the opposite direction by applying some chemicals to return the functional group of the resin back to its original state for reuse. For example, the cationic resin as described above is regenerated by a strong acid, in which the resin removes the adsorbed cations and combines with H+ to restore the original composition.

Weakly Acidic Cation Exchange Resin

This resin contains weakly acidic groups, such as carboxyl group: -COOH, which can electro-dissociate H+ ions in solutions and therefore present acidic. The negatively charged groups contained in the matrix after the resin is dissociated, such as R–COO- (R as for Styrene-divinylbenzene Copolymer Matrix base), can adsorb and combine other cations within the solution. The acidity and ionization capability of this resin are weak, so it is hard to electro-dissociate and exchange ions at lower PH levels. Only work in alkaline, neutral, or slightly acidic solutions in which PH values range from 5 to 14. And these resins are also regenerated with acids(more likely to be regenerated than strongly acidic resins).

Strongly Basic Anion Exchange Resin

This resin contains a strongly alkaline group such as the quaternary amine group (also known as quaternary amine group), -NR3OH, which can electro-dissociate OHions in solutions and therefore presents strongly alkaline. The positively charged group as in NR3+ of this resin can adsorb and combine other anions within the solution, therefore exchanging anions.

The electrolysis ability of this resin is strong enough to dissociate and exchange ions under any PH level. And in most cases, it is regenerated with strong alkali as NaOH.

Weakly Basic Anion Exchange Resin

This resin contains weakly alkaline groups such as primary amine group -NH2, secondary amine group as in-NHR, and tertiary amine group as in-NR2, which can electro-dissociate OHions in solutions and therefore presents weakly alkaline. These positively charged groups of this resin can adsorb and combine, which is to exchange anions from the solution.

This resin in most cases adsorbs all other acid molecules in the solution hence it can only work under neutral or acidic conditions(eg. PH 1-9). And it can be regenerated with Na2CO3 and NH4OH.

History of Ion Exchange Resins

Ion exchangers are a class of substances that can exchange ions, typically classified into inorganic ion exchangers such as zeolites and organic ion exchangers, of which organic ones are also known as ‘ion exchange resins ‘. In WWII, USA chemists obtained the patent for synthesizing styrene-based and acrylic-based ion exchange resins of poly-addition type, with fairly more stable chemical and physical properties as well as more economical compared to poly-condensed ion exchange resins, which initiated the foundation of today’s methods for manufacturing ion exchange resins. China started research on ion exchange resins ever since 1950 and as of 1958, domestically ion exchange resins were officially put into industrial production. At present, the varieties of resins made in China are over 60 and the quality is constantly improving and playing a crucial role in China’s economic development.