Question

function of NaOH in metallurgy of aluminium??

Answer 1

concentration of aluminum is carried out digesting the powdered ore with a concentrated solution of NaOH at 473-523k and 35-36bar pressure. this way , Al2O3is leached out as sodium aluminate. I.e.
Al2O3(s)+2NaOH (aq)+3H2O--> 2Na [Al (OH) 4](aq)

Answer 2

The ore of aluminium usually contains a Sio2,iron oxide and titanium oxide as impurities. Concentration of bauxite ore is carried out by digesting the powdered with a concentrated solution of NaOH at 473-523 K and 35-36 bar pressure. This way Al2o3 is leached out as sodium aluminate leaving behind the impurities.

Al2o3(s)+2NaOH(aq)+3H2O(l)—› 2Na[Al(OH)4](aq)