How can you separate alumina from silica in a baxuite ore associated with silica? Give equations, if any.

Solution

Aluminium bauxite is carried out by digesting the powdered ore with a concentrated solution of NaOH at 473 – 523 K and 35 – 36 bar pressure.

Al₂O₃(s)+2NaOH(aq) +3H₂O(l)→ 2Na[Al(OH)₄(aq)

The aluminate in solution is neutralised by passing CO₂ gas and hydrated Al₂O₃ is precipitated:

2Na[Al(OH)₄](aq) + CO₂(g) → Al₂O₃.xH₂O(s) + 2NaHCO₃(aq)
The sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al₂O_3.

${Al}_{2} O_{3} . {xH}_{2} O (s) \overset{1470 K}{\to} {Al}_{2} O_{3} (s) + {xH}_{2} O (g)$

Some More Questions From General Principles And Processes of Isolation Of Elements Chapter

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General Principles And Processes Of Isolation Of Elements

How can you separate alumina from silica in a baxuite ore associated with silica? Give equations, if any.

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