Comparison of Techniques for Electrowinning Tungsten from Scheelite.
Gomes JM; Uchida K; Wong MM
NTIS: PB 205 506 :10 pages
Two techniques were investigated for removing cao from scheelite (cawo4) prior to electrolysis. In the first technique, a crude tungstic oxide (wo3) containing 0.15 percent lime (cao) was prepared by digesting scheelite concentrates in hot hydrochloric acid. This oxide was used as cell feed to produce tungsten of 99.9-percent purity. The second technique used a high-temperature, two-phase separation, resulting in the extraction of 99 percent of the wo3 in the halide-tungstate phase, while 90 percent of the cao was retained in the silicate phase. Tungsten of 99.9-percent purity was deposited from the halide-tungsten melt after b2o3 and napo3 were added to form an electrolyte. The two methods were compared with a previously developed technique of depositing tungsten from scheelite concentrate fed directly to the electrolytic cell.
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