A solution of a chemical compound used to restore the capacity of an ion exchange system. Sodium chloride brine is used as a regenerant for ion exchange water softeners, and acids and bases are used as regenerants for the cation and anion resins used in demineralization.

A solution of a chemical used to restore the capacity of an ion exchange or oxidation system.

In ion exchange or softening applicatinos, a regenerant is the chemical solution used to restore an exhausted bed of ion exchange resin to the fully ionic (regenerated) form necessary for the desired ion exchange to again take place effectively. Regenerants are also used in a similar fashion to restore catalyst (e.g., iron and manganese removal) media for reuse.