Abstract: Recovery of molybdenum from a solid mixture, such as an exhausted catalyst, containing molybdenum in the oxide form or in the form of molybdic ions and other metallic compounds.The mixture is contacted with an aqueous alkali metal hydroxide to solubilize molybdenum in the form of an alkali metal molybdate, and after filtration the aqueous solution of alkali metal molybdate thus obtained is contacted with a strong cationic exchange resin to convert said molybdate into molybdic acid.

Abstract: Preparation of a catalyst based on molybdenum and iron oxides by precipitation from a soluble molybdenum compound and a soluble ferric salt, with separation of the precipitate from its mother waters and washing with deionized water.Molybdic ions are recovered from the mother waters and washing waters by contacting the latter with a salified anionic exchange resin, which is then contacted with aqueous alkali metal hydroxide to yield an aqueous solution of alkali metal molybdate.The molybdenum thus recovered may be recycled to the precipitation step upon conversion of the molybdate into molybdic acid by treatment with a strong cationic exchange resin, and possible conversion of the acid into ammonium paramolybdate.