Ion exchange is a kind of liquid-solid contrary process, which involves the diffusion process of matter in liquid and solid phases. At ambient temperature, the exchange reaction is fast, not the control factor. If the exchange of ions in the liquid phase of the slow diffusion, called external diffusion control, if the diffusion in the solid phase is slower, then called internal diffusion control.
The main types are: ① stirring groove (see mass transfer equipment), suitable for processing viscous liquid. When a single-level exchange does not meet the requirements, it can be cascaded with multilevel. ② fixed-bed ion exchanger, also known as ion Exchange column, is used for ion exchange fixed bed mass transfer equipment, the most widely used. Mobile Bed ion exchanger, is used for ion exchange mobile bed mass transfer equipment, because technical difficulties have not yet been industrial applications.