Selection factors and methods of ion exchange resins

The selection factors and methods of ion exchange resins are different: some ions are easily adsorbed by resins, but they are difficult to be replaced by "down". Some ions are difficult to be adsorbed by bleaching bed resins, but they are easy to be replaced. This property is called selectivity of anion exchange resins.

The selectivity of ion exchange resins is related to the following factors:

The more ion charges, the easier to be adsorbed by anion exchange resin. 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. For example, divalent ions are easier to adsorb than univalent ions.

2. For ions with the same charge, large atom-level ions are easier to adsorb. 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.

Compared with dilute solution, low-valent ions are easily adsorbed by resin in concentrated solution. 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. Generally speaking, for H-type strong acidic anion exchange resin, the order of ion selection in water. For OH type strong basic anion exchange resin, the order of anion selection in water is discussed. The selectivity of this anion exchange resin is helpful for the analysis and judgment of chemical water treatment process.

ion exchange resin

For ease of use, the density of anion exchange resin can be expressed by the following two methods:

1. Real wet density. Wet true density refers to the true density of anion exchange resin after fully expanding in water. The particle size here does not include the voids between resin particles. The wet true density is related to backwashing delamination and resin settling performance. The relative density is 1.04-1.30, the positive resin is 1.24-1.29, and the anionic resin is 1-06-1.11.

ion exchange resin

2. Apparent wet density. Wet apparent density, also known as wet pile density, refers to the volume density of anion exchange resin fully expanded in water. The bulk volume here includes the voids of anion exchange resin particles. The wet apparent density is usually used to calculate the number of resins to be filled in the exchange bed. The apparent density of anion exchange resin is generally 0.65-0.85, and that of anion exchange resin is 0.60-0.80. What is the temperature requirement of anion exchange resin? The anion exchange resin has certain heat resistance. When the service temperature exceeds the temperature limit it can withstand, the resin is easily destroyed by thermal decomposition. Generally speaking, the anion exchange resin can withstand 80 C, the weak base anion exchange resin can withstand 100 C and the strong base anion exchange resin can withstand 60 C. The optimum temperature for desilication is below 40 C.