How is red cake produced during vanadium processing?

During vanadium processing, red cake is produced through the following steps:

• Preparation: Vanadium-bearing ores or slags are crushed, ground, screened, and mixed with a sodium salt, such as sodium chloride or sodium carbonate.
• Roasting: The mixture is roasted at approximately 850° C (1,550° F) to convert the oxides into sodium metavanadate.
• Leaching: The resulting material is leached in hot water.
• Precipitation: The leachate is treated with sulfuric acid (acidulation), which causes the vanadium to precipitate as sodium hexavanadate. This compound is known as red cake.1

Once produced, red cake can be fused at 700° C (1,300° F) to yield technical-grade vanadium pentoxide, or it can be further purified by dissolving it in an aqueous solution of sodium carbonate to remove impurities like iron, aluminum, and silicon.1