ion exchange resin
Ion exchange resin is a polymer compound with functional groups (active groups that exchange ions), a network structure, and insolubility. Usually spherical particles. The full name of ion exchange resin consists of classification name, skeleton (or functional group) name, and basic name.
The pore structure is divided into gel type and macroporous type. Any resin with physical pore structure is called macroporous resin, and “macropore” is added before the full name. For those classified as acidic, add “yang” before the name, while for those classified as alkaline, add “yin” before the name.
Classification of ion exchange resin
Ion exchange resins can also be divided into styrene based resins and acrylic based resins based on the type of matrix. The types of chemically active groups in a resin determine its main properties and categories. Firstly, it can be divided into two categories: cationic resin and anionic resin, which can exchange ions with cations and anions in solution, respectively. Cationic resins are further divided into two categories: strong acidic and weak acidic, while anionic resins are further divided into two categories: strong alkaline and weak alkaline (or further divided into medium strong acid and medium strong alkaline).
Strong acidic cation Ion exchange resin
This type of resin contains a large number of strongly acidic groups, such as sulfonic acid group SO3H, which is prone to dissociation of H+in solution, resulting in strong acidity. After resin dissociation, the negatively charged groups contained in the body, such as SO32-, can adsorb and bind other cations in the solution. These two reactions cause the H+in the resin to exchange with the cations in the solution. Strong acidic resins have strong dissociation ability and can undergo ion exchange in both acidic and alkaline solutions.
After a period of use, the resin needs to undergo regeneration treatment, which involves using chemicals to reverse the ion exchange reaction and restore the functional groups of the resin to their original state for reuse. The cationic resin mentioned above is regenerated with strong acids, where the resin releases the adsorbed cations and then combines with H+to restore its original composition.
Weakly acidic cationic resin
This type of resin contains weakly acidic groups, such as carboxyl COOH, which can dissociate H+in water and become acidic. The remaining negatively charged groups after resin dissociation, such as R-COO – (R is a hydrocarbon group), can adsorb and bind with other cations in the solution, resulting in cation exchange. This resin has weak acidity or dissociation, making it difficult to dissociate and exchange ions at low pH, and can only function in alkaline, neutral, or slightly acidic solutions (such as pH=5-14). This type of resin is also regenerated with acid (which is easier to regenerate than strongly acidic resins).
Strong alkaline anion resin
This type of resin contains strong alkaline groups, such as quaternary amino group (also known as fourth order amino group) – NR3OH (R is a hydrocarbon group), which can dissociate OH – in water and become strongly alkaline. The positively charged groups of this resin can adsorb and bind with anions in the solution, resulting in anion exchange.
This resin has strong dissociation and can work normally at different pH levels. It is regenerated using strong alkalis such as NaOH.
Weakly alkaline anion resin
This type of resin contains weakly alkaline groups, such as primary amino group (also known as primary amino group) – NH2, secondary amino group (secondary amino group) – NHR, or tertiary amino group (tertiary amino group) – NRR, which can dissociate OH – in water and become weakly alkaline. The positively charged groups of this resin can adsorb and bind with anions in the solution, resulting in anion exchange. This type of resin in most cases adsorbs the entire other acid molecules in the solution. It can only operate under neutral or acidic conditions (such as pH=1-9). It can be regenerated with Na2CO3 and NH4OH.
Application fields of ion exchange trees in water treatment
The demand for ion exchange resins in the field of water treatment is high, accounting for about 90% of the production of ion exchange resins, used for the removal of various anions and cations in water. At present, the maximum consumption of ion exchange resins is used for pure water treatment in thermal power plants, followed by atomic energy, semiconductor, electronic industries, etc.
Saving method
Ion exchange resins cannot be stored in the open air. The temperature of the storage area is 0-40 ℃. When the temperature of the storage area is slightly lower than 0 ℃, clear saturated salt water should be added to the packaging bag to soak the resin. In addition, when the storage temperature is too high, it not only makes the resin easy to dehydrate, but also accelerates the degradation of the anion resin. Once the resin loses water, it cannot be directly added with water during use. It can be soaked in clear saturated salt water, and then gradually diluted with water to wash away the salt. During storage, it should be kept moist.