[en] Vanadium pentoxyde oxydation catalyzers (5 to 8%) are utilised in SO₄H₂ plants and represent a world market of approximately 17 500 t (2 500 to 3 000 t for Europe only). Used catalyzers, very few of them being retreated, are very seldom utilized for the preparation of ferro-vanadium, so that the existing stocks in western Europe would amount to about 15 000 t. Present solutions are the disposal in dump areas or the storage in barrels in underground mines. Cogema has studied an hydrometallurgical process allowing an easy recovery of vanadium. A sulfuric attack in special conditions solubilises 95% of the vanadium, the following purification process consisting in the extraction of vanadium at the valence 4 with di(ethylhexyl)phosphoric acid, at a pH of 2 and its de-extraction with unimolar SO₄H₂. Purified vanadium is then precipitated with ammonia, and roasted at 580 deg C in order to get a high purity product. (author). 6 refs., 21 tabs., 2 figs