Softening resin knowledge point

Water treatment resin is divided into cationic resin and anionic resin, cationic resin and subdivided into sodium and hydrogen type, sodium type resin will water calcium and magnesium ions exchange into sodium ions, make water soft. Hydrogen resin is the exchange of calcium and magnesium ions in the water into hydrogen ions to soften the water. Anionic resin containing replaceable hydroxide ions can replace the acid ions in the water, at the same time the use of anionic resin and hydrogen type cationic resin can be turned into pure water.

In the water treatment industry, ion exchange is the reaction of ions in water and ions in ion exchange resin by equal charge molar amount.

Physical properties

The particle size and related physical properties of ion exchange resin have a great influence on its work and performance.

Resin particle size

Ion exchange resins are usually made into small beads, and their size is also important. The resin particles are smaller, the reaction speed is larger, but the fine particles of liquid through the resistance are greater, the need for higher working pressure; Especially the high viscosity of concentrated sugar liquid, this effect is more significant. Therefore, the size of resin particles should be selected appropriately. If the resin particle size is below 0.2mm(about 70 mesh), it will significantly increase the resistance of fluid flow, reduce flow and production capacity.

Resin particle size is usually determined by the wet screening method, the resin in full water absorption and expansion after screening, the cumulative value of 20, 30, 40, 50……The retention of 90% of the particles on the mesh screen can pass through its corresponding mesh diameter, known as the “effective particle size” of the resin. The effective particle size of most general resin products is between 0.4 and 0.6mm.

The uniformity of resin particles is indicated by the uniformity coefficient. It is in the determination of resin “effective particle size” to take the cumulative retention of 40% particles, corresponding to the ratio of mesh diameter and effective particle size. For example, the effective particle size of a resin (IR-120) is 0.4 ~ 0.6mm, and the particles retained on the 20-mesh screen, 30-mesh screen, and 40-mesh screen are 18.3%, 41.1%, and 31.3% respectively, then the uniformity coefficient is calculated to be 2.0.

Density of resin

The density of the resin at drying is called the true density. The weight of the wet resin per unit volume (including intergranular Spaces) is called apparent density. The density of the resin is related to its degree of cross-linking and the nature of the groups exchanged. Generally, the density of high crosslinking resin is higher, the density of strong acid or strong basic resin is higher than that of a weak acid or weak base, and the density of large pore resin is lower.

Solubility of resins

Ion exchange resins should be insoluble substances. However, the resin in the synthesis process of inclusion of the polymerization of the lower degree of material, and the decomposition of the material generated by the resin, will be dissolved in the operation. Resins with a lower crosslinking degree and more active groups tend to dissolve more.

The degree of expansion of the resin