How is technical-grade vanadium pentoxide made from red cake?

To produce technical-grade vanadium pentoxide from red cake (sodium hexavanadate), the compound is fused at 700° C (1,300° F). This process yields a product that contains at least 86 percent vanadium pentoxide ($V_2{O}_5$).1

If higher purity is required, the red cake can be further processed by dissolving it in an aqueous solution of sodium carbonate. During this stage, impurities such as iron, aluminum, and silicon are precipitated from the solution by adjusting the acidity. The vanadium is then precipitated as ammonium metavanadate through the addition of ammonium chloride, filtered, and finally calcined to produce vanadium pentoxide with a purity exceeding 99.8 percent.1