Detailed Explanation of Ion Exchange Resin Density in Ultrapure Water Production Process

The density of ion exchange resins is primarily determined by the amount of crosslinking agent added during preparation. It is generally classified into two types: wet true density and wet apparent density in the hydrated state. Wet true density = wet resin mass (g) / resin particle volume (mL); Wet apparent density = wet resin mass (g) / resin bulk volume (mL). The wet true density of ion exchange resins varies depending on the chemical groups involved. Generally, the wet true density of strongly acidic cation exchange resins is approximately 1.3 g/mL, while that of strongly basic anion exchange resins is approximately 1.1 g/mL. Introducing materials with high relative density, such as zirconium phosphate or zirconium oxide, or adding more sulfonic acid groups to the ion exchange resin can increase its wet true density value. In mixed-bed or double-bed ion exchange resins, increasing the difference in wet true density between the two resins can effectively promote their separation.

The wet apparent density of ion exchange resins is an important reference for designing ion exchange devices. Its wet apparent density is affected by the amount of crosslinking agent added during the synthesis of the resin and the active groups. The more crosslinking agent added, the greater the degree of crosslinking, and the greater its wet apparent density. In addition, among the active groups of ion exchange resins, resins with strong acid and strong base groups have higher wet apparent density than resins with weak acid and some base groups. Gel-type resins have higher wet apparent density than the corresponding macroporous resins.