The invention relates to a method for preparing alkali metal ferrates, characterized in that it includes the following steps: (i) a mixture is prepared which includes at least one alkali or alkaline-earth metal hypochlorite, at least one iron salt, and at least one hydroxide of an alkali metal; (ii) an inert material in solid particle form is added to the mixture of (i); (iii) the compounds of (ii) are agitated and allowed to react; (iv) the reaction mixture obtained in (iii) is cooled so as to keep its temperature between 50°C and 90°C; (v) the formed alkali metal ferrate grains are recovered by sieving.
