Question

What is red mud and is it removed ?

Answer 1

1. Red mud is referred to insoluble impurities consisting of sand, ferric oxide, etc. generated in the production of alumina from bauxite.
2. It is left after bauxite is dissolved in sodium hydroxide$\left(\mathrm{NaOH}\right)$ forming sodium meta aluminate using the Bayer process.

$$\begin{gathered} {\mathrm{Al}}_2{\mathrm{O}}_3.2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{s}\right)+2\mathrm{NaOH}\left(\mathrm{aq}\right)\to 2{\mathrm{NaAlO}}_2\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{impurities} \\ \left(\mathrm{Bauxite}\right)\mathrm{sodium}\mathrm{meta} \\ \mathrm{aluminate} \end{gathered}$$

3. Red mud is removed by the filtration method by filtering off the particles through filter paper.