Electrowinning of Tungsten From Fused Bath Composed of Calcium Chloride, Calcium Oxide and Tungstic Oxide

[摘要] The electrolysis of tungstic oxide dissolved in the bath of calcium chloride and calcium oxide was studied to produce metallic tungsten using carbon as anode and iron as cathode in the temperature range of 900¢ª to 1200 ¡É. The binary phase diagrams CaCl2-CaO and CaCl2-CaWO4 systems were constructed to determine the suitability of bath composition and the range of temperatures for the electrolysis. As WO3 reacted with CaCl2 to form oxychloride in the fused salt, the addition of the proper amount of CaO was necessary to avoid the loss of WO3. The optimum compositions of fused bath were CaCl2 100 parts, CaO and WO3 each 10 to 20 parts, with the CaO, WO3 ratio greater than unity, to keep freezing point low and to prevent the vaporization of CaCl2. The observed decomposition voltage at which WO3 decomposes to W and CO was-0.1 volt, whereas the calculated was -0.3 volt. Metallic tungsten deposited at the cathode reacted easily with CO formed secondarily at the anode surface, to form WC below 1050 ¡É, so that the cell temperature should be above 1050 ¡É. The effects of cathode current densities on current efficiency were minor in the range of 1 to 5 amp/cm2.

[学科分类] 化学（综合）