Question

In Bayer’s leaching process, the siliceous impurities $\left(Si{O}_2\right)$ are filtered out immediately after leaching with NaOH – True or False?

• A. True
• B. False

Answer 1

The correct option is B

False

Red Bauxite contains $A{l}_2{O}_3.2H_{2}O$ $+F{e}_2{O}_3$ (major impurity) + $Si{O}_2$ $+Ti{O}_2$

After calcination, organic matter, volatile substances and moisture are removed. The calcine is then leached with 45 % NaOH solution at about ${150}^{\circ }C$ where

Note that only $Ti{O}_2$ and $F{e}_2{O}_3$ are filtered out.