The present invention relates to the use of inorganic salts for increasing the adsorption of oxoanions and/or thioanalogues thereof to metal-doped ion exchangers, preferably to iron oxide/iron oxyhydroxide-containing ion exchangers, preferably from water or aqueous solutions, and also the conditioning of these metal-doped ion exchangers having increased adsorption behaviour toward oxoanions and/or thioanalogues thereof by using inorganic salts with the exception of amphoteric ion exchangers which have both acidic and basic groups as functional groups.