Backwashing Principle of Ion Exchange Resin

Ion exchange resins are a class of macromolecule compounds with functional group network structure. They are composed of three-dimensional insoluble network structure, functional groups on the skeleton and exchangeable ions with opposite charges on the functional groups. Ion exchange resins can be divided into styrene resin and acrylic resin according to their matrix types. The main properties and types of resins are determined by the types of chemical active groups in resins. Firstly, it can be divided into cationic resins and anionic resins, which can exchange ions with cations and anions in solution respectively. Cationic resins can be divided into strong acidity and weak acidity. Anionic resins can be divided into strong alkalinity and weak alkalinity. Ion exchange resins can be divided into cation exchange resins, anion exchange resins and amphoteric ion exchange resins. Ion exchange resins are insoluble in water and general solvents. Ion exchange resins have high mechanical strength, stable chemical properties and long service life under normal conditions. Cationic resins and anionic resins are classified into two groups according to their chemical active groups. Cationic resins can be divided into strong and weak acids. Anionic resins can be divided into strong alkalinity and weak alkalinity. In the process of ion exchange, the principle of ion exchange resin is: H + exchange between cation and cation exchange resin, cation transfer in water to anion resin, H + exchange in water. Anions in water are exchanged with anion exchange resin on OH - and anions in water are transferred to Zinda resin. OH - on resin is exchanged in water.

　　1 and Strong Acidic Cationic Resin

　　It contains a large number of strong acidic groups, such as sulfonic acid-SO3H, which are easily separated from H + in solution, so they are strong acidic. After resin dissociation, the negative ions contained in the body can adsorb other cations in the solution. Strong acidic resin has strong dissociation ability and can exchange ion in acidic or alkaline solution. After a period of time, the resin should be regenerated, i. e. the ion exchange reaction takes place in the opposite direction to the chemical substance, so that the functional groups of the resin can be restored to their original state for reuse.

　　2 and weakly acidic cationic resins

　　Containing weak acidic groups, such as carboxyl-COOH, they can separate H+ from water and become acidic. Ion exchange resins can be divided into styrene resin and acrylic resin according to their matrix types. The main properties and types of resins are determined by the types of chemical active groups in resins. Firstly, it can be divided into cationic resins and anionic resins, which can exchange ions with cations and anions in solution respectively. Cationic resins can be divided into strong acidity and weak acidity. Anionic resins can be divided into strong alkalinity and weak alkalinity. Ion exchange resin is composed of classification name, skeleton (or gene) name and basic name. The pore structure is divided into two types: gel type and large pore type. All macroporous resins with physical pore structure are added "big hole" before the full name. If the classification is acidic, the word "yang" should be added before the name, while the classification is alkaline, and the word "yin" should be added before the name. Such as: macroporous strong acidic styrene cation exchange resin. Residual anions after resin dissociation can be adsorbed with other cations in solution to form cation exchange. The resin has weak acidity and is difficult to dissociate and exchange ions at low pH. It can only be used in alkaline, neutral or slightly acidic solutions (e.g. PH5-14). These resins are also regenerated with acid (which is easier to regenerate than strong acidic resins).

　　3 and Strong Basic Anionic Resin

　　Contains strong alkaline groups, such as quaternary amines (also known as quaternary amines) - NR3OH (R is a hydrocarbon group), OH - can be dissociated in water, with strong alkalinity. The positive group of the resin can be adsorbed with anions in the solution, resulting in anion exchange. The resin has strong dissociation and can work normally at different pH values. It is regenerated from a strong foundation.

　　4 and weak basic anion resins

　　It contains weak alkaline groups and can separate OH - from water, showing weak alkalinity. The positive group of the resin can be adsorbed with anions in the solution, resulting in anion exchange. In most cases, this Zinda adsorbs all the other acidic molecules in the solution. It can only work in neutral or acidic conditions, such as PH1-9. Na2CO3 and NH4OH are renewable.