Water treatment resin is divided into cation resin and anion resin. Cation resin is divided into sodium type and hydrogen type. Sodium type resin exchanges calcium and magnesium ions in water into sodium ions, which makes water soft. Hydrogen resin is to exchange calcium and magnesium ions into hydrogen ions to soften the water. The anion resin contains replaceable hydrogen ions, which can replace the acid ions in the water. At the same time, the anion resin and hydrogen cation resin can be used to change the water into pure water.
In the water treatment industry, ion exchange is the reaction of equal charge molar quantity between the ions in the water and the ions on the ion exchange resin.
Physical properties the particle size of ion exchange resin and the related physical properties have a great influence on its work and performance.
Resin particle size ion exchange resin is usually made into small beads, and its size is also very important. When the resin particles are smaller, the reaction speed is larger, but the resistance of the fine particles to the liquid is larger, which requires higher working pressure; especially when the viscosity of concentrated sugar liquid is higher, the effect is more significant. Therefore, the size of resin particles should be appropriate. If the resin particle size is less than 0.2mm (about 70 mesh), the resistance of fluid flow will be increased obviously, and the flow rate and production capacity will be reduced.
The size of resin particles is usually determined by wet sieving method. The resin is sieved after full water absorption and expansion, and the accumulated value is 20, 30, 40, 50 90% of the particles in the mesh can pass through the corresponding mesh diameter, which is called the "effective particle size" of resin. The effective particle size of most general resin products is between 0.4 and 0.6mm.
Whether the resin particles are uniform is indicated by uniformity coefficient. It is to measure the "effective particle size" of the resin, take the cumulative retention of 40% particles, the corresponding proportion of the mesh diameter and the effective particle size. If the effective particle size of a resin (IR-120) is 0.4-0.6mm, the retained particles on 20 mesh sieve, 30 mesh sieve and 40 mesh sieve are 18.3%, 41.1% and 31.3%, respectively, then the calculated uniformity coefficient is 2.0.
The density of a resin the density of a resin when it is dry is called true density. The weight per unit volume of wet resin (even the space between particles) is called apparent density. The density of resin is related to its crosslinking degree and the properties of exchange group. Generally, the density of resin with high degree of cross-linking is higher than that of resin with strong acid or strong alkali, while that of resin with large pore is lower.
The soluble ion exchange resin of resin shall be insoluble substance. However, the substances with low polymerization degree and the substances generated by resin decomposition will dissolve out during the operation. The resin with low degree of crosslinking and more active groups has a higher tendency of dissolution.
The expansion degree of the resin ion exchange resin contains a large number of hydrophilic groups, which will absorb water and expand when contacting with water. When the ion in the resin changes, for example, the cation resin changes from H + to Na +, and the anion resin changes from Cl - to OH -, both of which expand due to the increase of ion diameter and increase the volume of the resin. In general, the resin with low crosslinking degree has larger expansion degree. In the design of ion exchange device, the expansion degree of resin must be considered to adapt to the change of resin volume caused by ion conversion during production and operation.
The durability of the resin the particle of the resin has the change of transfer, friction, expansion and contraction when it is used, and there will be a little loss and breakage after long-term use, so the resin should have high mechanical strength and wear resistance. Generally, the resin with low crosslinking degree is easy to break, but the durability of the resin mainly depends on the uniformity and strength of the crosslinking structure. For example, macroporous resin with high crosslinking degree has stable structure and can withstand repeated regeneration.
Cation resin this kind of resin contains a large number of strong acid groups, such as sulfo-so3h, which is easy to dissociate H + in the solution, so it is strong acid. After dissociation of the resin, the body contains negative groups, such as SO3 -, which can absorb other cations in the solution. These two reactions make the H + in the resin and the cations in the solution exchange. The dissociation ability of strong acid resin is very strong, It can dissociate and produce ion exchange action in acid or alkaline solution. After the resin is used for a period of time, it needs to be regenerated. That is to say, use chemicals to make the ion exchange reaction proceed in the opposite direction, so that the functional group of the resin can return to the original state for reuse. For example, the above-mentioned cation resin is regenerated with strong acid, at this time, the resin will release the adsorbed cation, Then combine with H + to restore the original composition
(the content comes from the invasion and deletion of network arrangement)