Question -
Answer -
To separate alumina from silicain bauxite ore associated with silica, first the powdered ore is digested witha concentrated NaOH solution at 473 − 523 K and 35 − 36 bar pressure. Thisresults in the leaching out of alumina (Al2O3)as sodium aluminate and silica (SiO2) as sodium silicate leaving the impurities behind.
Then, CO2 gas is passed through the resulting solution toneutralize the aluminate in the solution, which results in the precipitation ofhydrated alumina. To induce precipitation, the solution is seeded with freshlyprepared samples of hydrated alumina.
During this process, sodiumsilicate remains in the solution. The obtained hydrated alumina is filtered,dried, and heated to get back pure alumina.
