RI 6742 Electrowinning Tungsten In Halide And Phosphate Electrolytes

Two molten salt systems were evaluated as electrolytes for the repetitive recovery of tungsten from tungsten oxide (W03) made by calcining commercial-grade ammonium paratungstate. Using a sodium chloride-sodium fluoride-potassium aluminum tetrafluoride electrolyte at 800° C, 1 pound of 99.8 percent tungsten was recovered for each 2.7 kilowatt-hours of energy consumed. The metal contained 1,100 ppm carbon, was in dendritic masses of spherical grains, and had an apparent bulk density of 5.41 g/cm3. T ngsten of 99.9 percent purity was won from a sodium pyrophosphate-sodium tetraborate-sodium chloride electrolyte at 1,000° C; 6.0 kilowatt-hours of energy was consumed for each pound of metal recovered. The metal contained 120 ppm carbon, was in dendritic masses of hexagonal acicular crystals, and had an apparent bulk density of 7.25 g/cm . Each metallic impurity--aluminum, calcium, copper, iron, nickel, and silicon--in the two tungsten products was 16 ppm or less.