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Definition And Classification Of Ion Exchange Resin

Jul 22, 2020

When it comes to ion exchange resin, many people may know that it is used to absorb cations such as calcium and magnesium in water, and anions such as hydroxide. The water tends to be pure water and the ion exchange resin can be used repeatedly after treatment, a good way to treat water. Speaking of what is deionized exchange resin? How to give it a definition?

   If we must give it a definition, we can say:

"Ion exchange resin" is a polymer compound with functional groups (active groups with exchange ions), network structure, and insoluble. Usually spherical particles.

   The full name of ion exchange resin is basically classified by classification name, skeleton (or gene) name, ion exchange resin:

"Ion exchange resins can also be classified into styrene resins and acrylic resins according to the type of matrix." The type of chemically active groups in the resin determines the main properties and types of the resin. Firstly, it can be divided into two categories: cationic resin and anionic resin, which can perform ion exchange with the cation and anion in the solution. Cationic resins are further divided into two categories, strong acid and weak acid, and anionic resins are further divided into two categories, strong alkaline and weak alkaline (or medium strong acid and medium strong alkaline). , Basic name composition.

  basic type

   Strong acid cationic resin

   This type of resin contains a large number of strong acid groups, such as sulfonic acid group -SO3H, which easily dissociates H+ in the solution, so it is strongly acidic. After the resin dissociates, the negatively charged groups contained in the body, such as SO3-, can adsorb and bind other cations in the solution. The two ion exchange resins

The "reaction" exchanges H+ in the resin with cations in the solution. Strong acid resin has strong dissociation ability, and can dissociate and produce ion exchange in acid or alkaline solution.

After using for a period of time, the resin needs to be regenerated, that is, the ion exchange reaction is carried out in the opposite direction with chemicals to restore the functional groups of the resin to its original state for reuse. The above-mentioned cationic resin is regenerated with strong acid. At this time, the resin releases the adsorbed cations, and then combines with H+ to restore the original composition.

   Weak acid cationic resin

   This kind of resin contains weakly acidic groups, such as carboxyl -COOH, which can dissociate H+ in water and become acidic. After the resin dissociates, the remaining negatively charged groups, such as R-COO- (R is a hydrocarbon group), can be combined with other cations in the solution to produce cation exchange. The acidity of this resin is weak, and it is difficult to dissociate and perform ion exchange at low pH. It can only work in alkaline, neutral or slightly acidic solutions (such as pH 5-14). This kind of resin is also regenerated with acid (it is easier to regenerate than strong acid resin).

  Strong basic anion resin

   This type of resin contains a strong basic group, such as a quaternary amine group (also known as a quaternary amine group) -NR3OH (R is a hydrocarbon group), which can dissociate OH- in water and become strongly basic. The positively charged groups of this resin can adsorb and combine with the anions in the solution to produce anion exchange.

  This kind of resin has strong dissociation and can work normally under different pH. It uses strong alkali (such as NaOH) for regeneration.

   Weakly basic anion resin

This type of resin contains weakly basic groups, such as primary amino groups (also known as primary amino groups) -NH2, secondary amino groups (secondary amino groups) -NHR, or tertiary amino groups (tertiary amino groups) -NR2, They can dissociate from OH- in water and become weakly alkaline. The positively charged groups of this resin can be exchanged with solution ion exchange resins

The anions in    are adsorbed and combined to produce anion exchange. In most cases, this resin adsorbs all other acid molecules in the solution. It can only work under neutral or acidic conditions (such as pH 1-9). It can be regenerated with Na2CO3 and NH4OH.

   Transformation of ionic resin

   The above are the four basic types of resin. In actual use, these resins are often converted to other ionic types to meet various needs. For example, the strong acid cationic resin is often reacted with NaCl to convert it into a sodium-type resin for reuse. When working, the sodium-type resin releases Na+ and exchanges and adsorbs Ca2+, Mg2+ and other cations in the solution to remove these ions. No H+ is released during the reaction, which can avoid the pH drop of the solution and the resulting side effects (such as sucrose conversion and equipment corrosion, etc.). After the resin is used in sodium form, it can be regenerated with brine (without strong acid). Another example is the anion resin can be converted to chlorine type and used again. It releases Cl- and absorbs and exchanges other anions during work. Its regeneration only needs to use salt water solution. Chlorine resin can also be converted to bicarbonate (HCO3-) operation. Strong acid resins and strong alkaline resins no longer have strong acidity and strong alkalinity after being converted into sodium and chlorine types, but they still have other typical properties of these resins, such as strong dissociation and wide working pH range Wait.

   The above is some small knowledge obtained from consulting related materials, I hope it will be helpful to everyone, welcome everyone.