Refractory metal recovery process

Details Refractory metal recovery process Refractory metal recovery process

C - Chemistry, Metallurgy

22

B

53/118

C22B 34/00 (2006.01) C22B 34/22 (2006.01) C22B 34/30 (2006.01)

Patent

CA 1165126

REFRACTORY METAL RECOVERY PROCESS Abstract of the Disclosure Disclosed is a process for recovering chromium, vana- dium, molybdenum, and tungsten from secondary resources such as alloy scrap comprising a refractory metal and base metals such as cobalt, nickel, iron, and copper. The scrap is calcined with sodium carbonate in air to convert the refractory metal values to Mo04=, VO4?, W04=, and Cr04= and the base metals to water insol- uble oxides. A leach of the calcined materials produces a pregnant liquor rich in refractory metals which, after separation of the vanadium, molybdenum and tungsten values, is treated with C0, CHOO-, CH30H, or HCHO to reduce Cr+6 to Cr+3. The carbonate and bicarbonate salts produced as a byproduct of the reduction are recycled to the calcination stage. As a result of the V, W, and Mo partition, a mixed solid comprising Ca0?nV205, CaMo04, and CaW04 is produced. This is treated with carbonated water or formic acid to selectively dissolve vanadium values which are subsequently recovered by pre- cipitation or extraction. The remaining mixed CaW04 and CaMo04 solid is treated with H202 and sulfuric acid to reject a Mo and W-free CaS04 precipitate, and to produce a concentrated solution of tungsten and molybdenum. The W values are selec- tively precipitated from this solution by decomposing the peroxy complexes. The process has the advantages that a wide variety of different feed materials can be treated, no energy intensive pyrometallurgy is involved, reagent consumption is minimized, and no aqueous effluents are produced. -1-

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