GB867484A - Improvements in the production of vanadium pentoxide - Google Patents

Abstract

Vanadium pentoxide is produced from materials containing oxidic compounds of vanadium and alkali metal values by forming an ammoniated aqueous solution containing vanadium which is, or has to be converted to the pentavalent state, adjusting the ammonium to alkali metal ion ratio to at least 2.1, heating the aqueous solution between 75 and 90 DEG C., adjusting the pH to 2.1 with an acid thereby forming water soluble salts of alkali metals and precipitating an ammonium polyvanadate. The polyvanadate is then heated under oxidizing conditions at 190 to 400 DEG C. forming vanadium pentoxide which is thereafter fused at 670 to 950 DEG C. The initial oxidic compound of vanadium may be an alkali metal vanadate, a hydrous vanadium oxide or a mixture thereof and normally results from the salt roasting of vanadium containing ores such as carnotite. In an illustrated sequence an alkali metal hexavanadate is dissolved in ammonium hydroxide to form a solution containing to 1 to 5% V2O5 having a pH of 8. Such solution is then treated with hydrogen peroxide or potassium permanganate, to oxidize the vanadium to the pentavalent state. The resulting metavanadate solution heated to 80 DEG C., is treated with ammonia until the ammonium ion/alkali metal ion ratio is at least 2:1 and sulphuric acid then added to bring the pH to 2:1 and the mixture digested at 75 DEG C. Ammonium hexavanadate precipitated leaving a solution of alkali metal sulphates. The polyvanadate precipitate was washed and dried at 180 DEG C., re-dissolved in concentrated ammonium hydroxide and reprecipitated by the addition of sulphuric acid; the purified product was fused at 400 DEG C. and thereafter heated to 700 DEG C. to form a molten vanadium pentoxide product, which was solidified in the form of flakes.