In leaching of alumina from bauxite by Bayer’s process, then ore is treated with

In leaching of alumina from bauxite by Bayer’s process, the ore is treated with NaOH (aq). Concentration is carried out by heating the powdered ore with a concentrated solution of NaOH at $473-523K$ and 35 – 36 bar pressure. $A{l}_2{O}_3$ is extracted out as sodium aluminate.
$A{l}_2{O}_3\left(s\right)+2NaOH\left(aq\right)+3H_{2}o\left(l\right)\to 2Na\left[Al{\left(OH\right)}_4\right]\left(aq\right)$
The sodium aluminate formed is neutralised by passing $C{O}_2$ gas and hydrated $A{l}_2{O}_3$ is precipitated.
$2Na\left[Al{\left(OH\right)}_4\right]\left(aq\right)+C{O}_2\left(g\right)\to A{l}_2{O}_3.x{H}_{2}O\left(s\right)+2NaHC{O}_3\left(aq\right)$