In ion exchange or softening applications, 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. Sodium chloride brine is normally used to regenerate cation exchange water softeners and for some dealkalizer systems. Hydrochloric and sulfuric acids are used for hydrogen-form cation deionizations units. Sodium hydroxide is normally used to regenerate OH– form anion deionizations systems. Potassium permanganate regenerant is used to regenerate a manganese greensand iron and manganese removal filter.