The process of extracting alumina from bauxite involves several steps. Which of the following options correctly represents the order of these steps?
Leaching, precipitation, calcination
Calcination, leaching, precipitation
Precipitation, leaching, calcination
Calcination, precipitation, leaching
The process of extracting alumina from bauxite typically involves the following steps in the correct order:
Precipitation: Bauxite is dissolved in a hot concentrated solution of sodium hydroxide (NaOH) under pressure. This process is known as the Bayer process. The aluminium hydroxide present in the bauxite precipitates out as a solid.
Leaching: The solid aluminium hydroxide is then separated from the remaining impurities by filtration. It is washed to remove any remaining impurities, leaving behind purified aluminium hydroxide.
Calcination: The purified aluminium hydroxide is heated at high temperatures in a kiln, resulting in the decomposition of aluminium hydroxide to form alumina (aluminium oxide). This step is known as calcination.