Abstract: Process for the preparation of a composite solid material which fixes inorganic contaminants, based on metal hexacyanoferrate, comprising a solid support coated with a film of an anion-exchange polymer to which is fixed an insoluble metal hexacyanoferrate forming a thin layer, said process essentially comprising at least one step in which said solid support is brought into contact with at least one liquid reactant and at least one step in which washing is carried out with a washing liquid, characterized in that all of the steps of the process are carried out continuously in one and the same receptacle, such as a column, in which the support forms a fluidized bed, the fluidization of which is provided by said at least one reactant or washing liquid.