Ion exchange separation is widely used in:
- softening of water, preparation of high-purity water, purification of environmental wastewater.
- Purification of solutions and substances, such as extraction and purification of uranium.
- Separation of metal ions, enrichment of trace ions and removal of interference ions.
- Extraction and purification of antibiotics, etc.
The ion exchange reaction is reversible and proceeds equally. It is known from experiments that the cation exchange potential in dilute solution at room temperature increases with the increase of ion charge and radius; high molecular weight organic ions and metal complex anions have high exchange potential. Highly polarized ions such as Ag+, Tl+, etc. also have high exchange potentials. The ion exchange rate decreases with the increase of resin crosslinking degree, and increases with the decrease of particles. As the temperature increases, the concentration increases, and the exchange reaction rate also increases.
Ion exchange resin can be regenerated. Exchange the depleted ion exchange resin with appropriate acid, alkali or salt solution to convert the resin into the required form, which is called regeneration. Such acids, bases or salts are called regenerants.
The ion exchange process is often carried out in an ion exchanger. The ion exchanger is similar to a pressure filter, and the shell is a steel tank; the ion exchange usually adopts a filtering method, the filter bed is composed of exchanger, and the bottom is a pipe system with a filter head.
Ion exchange exchanges the ions in the solid ion exchanger with the ions in the dilute solution to extract or remove some ions in the solution. It is a unit operation belonging to the mass transfer separation process. Artificially synthesized ion exchange resins are widely used as ion exchangers. It is a poorly soluble polymer electrolyte with a network structure and ionizable active groups. According to the different active groups on the resin skeleton, it can be divided into cation exchange resin, anion exchange resin, amphoteric ion exchange resin, chelating resin and redox resin. The resin used for ion exchange separation is required to have insolubility, a certain degree of crosslinking and swelling, and the exchange capacity and stability should be high.