GB600833A - Method of extraction of vanadium from bauxites and manufacture of ferro-vanadium - Google Patents

Abstract

Relates to the extraction of vanadium from salts crystallizing from Bayer liquors consisting of sodium fluo-vanadate, fluo-phosphate and fluo-arsenate. The salts are dissolved in hot water, sulphuric or phosphoric acid is added for partial or complete neutralisation employing phenol-phthalein, and crystals of disodium phosphate, disodium arsenate and in some cases, sodium sulphate allowed to separate. The filtrate is treated by one of three methods: (1) Ammonium chloride or sulphate is added to precipitate ammonium metavanadate which is calcined in a closed vessel to produce V2O4 and V2O3; (2) Gaseous ammonia is introduced to precipitate all sodium salts other than the vanadate. The ammoniacal filtrate is thereupon (a) partially degassed by heating, and sulphuric or hydrochloric acid added to precipitate pure ammonium metavanadate, or (b) completely degassed, and sulphuric acid added to precipitate a sodium salt of hexametavanadic acid on heating to 100 DEG C. for some hours; (3) An aluminium salt is added in the presence of sulphuric acid to remove the fluorine as cryolite; calcium sulphate is added to the filtrate to precipitate calcium phosphate, on removal of which, sulphuric acid and sodium chlorate are added. After some hours at 100 DEG C. disodium hexametavanade precipitates. The calcium phosphate may be converted to phosphoric acid for use at the commencement of the process. The various sodium salts crystallizing in the above processes may be neutralized with sulphuric or phosphoric acid, disodium phosphate crystallizing from the cooled liquor. The mother liquors from recrystallizations of the phosphate, when rich enough in arsenic, are treated with caustic soda, trisodium fluoarsenate, for use in the manufacture of insecticides, crystallizing. The solution is then treated for the recovery of the vanadium as described. Ferrovanadium is obtained from the vanadium oxides, &c., produced (see Group II). The slags from this process are roasted at 700 DEG C., with the addition of sodium carbonate when necessary, to produce sodium vanadate, convertible if desired, to ammonium metavanadate.ALSO:Ferrovanadium containing say 50-60 per cent V and less than 0.1 per cent Al is produced by the reduction with powdered aluminium in the presence of iron of the lower oxides of vanadium. Thus there may be employed V2O4 containing up to 10 per cent V2O3 obtained by calcining ammonium metavanadate in a closed vessel. Disodium vanadate, partly reduced by coal, sawdust, &c. at 800-1,000 degrees C. may also be reduced by aluminium in the presence of iron.