How does the Bayer process link bauxite quality to aluminum hydroxide cost and availability?

Bauxite mineralogy fundamentally shapes aluminum hydroxide economics. Gibbsite-type ores dissolve readily in caustic at around 145°C, while boehmite needs roughly 220°C and diaspore—dominant in China—requires 260°C, making Chinese refining energy-intensive at 2.5 to 3 times the cost of overseas Bayer plants. This cost gap explains why Chinese producers focus on specialty hydroxide grades rather than competing purely on metallurgical alumina. The precipitation step, where sodium aluminate solution is seeded to crystallize aluminum hydroxide, is the critical control point for particle size and morphology. Producers targeting flame-retardant or filler applications must manage seed ratio, temperature profile, and residence time to achieve desired d50 and uniformity. Feedstock quality, measured by alumina-to-silica ratio, directly impacts yield and impurity levels in the final hydroxide product.