PURPOSE: To separate iron and a very small amount of elements easily with one processing by allowing a liquid solution containing iron and a very small amount to element to positive and negative ion exchange resins and a very small amount of element to be absorbed to at least one of them.

CONSTITUTION: A substance containing iron and a very small amount of element to be separated is prepared as aqueous solution of hydrofluoric. It is desirable that the hydrofluoric concentration contained in the aqueous solution should be of a 1-10 normal one. When the aqueous solution is allowed to contact a positive ion exchange resin, iron is not absorbed and transition metals such as Ni and Mn are adsorbed by resin. On the other hand, an element which exists as oxo acid ion of Mo and Sb is adsorbed by a negative ion exchange resin and iron cannot be adsorbed, thus separating iron and a very small amount of element. It is desirable that anion site should be -SO3- with polystyrene etc., as a support for the positive ion exchange resin and that cation site should be of quaternary ammonium ion with polystyrene etc., as a support for the negative ion exchange resin.