Bauxite is the most important source for Alumina (aluminium oxide) which is extracted by a leaching
method using caustic soda in a process known as the Bayer’s Process. Here, the simultaneously
acidic and basic aluminium oxides and hydroxides are separated by heating the bauxite ore to 150 to
200 degree Celsius in a pressure vessel along with a sodium hydroxide solution (caustic soda). In this
form of extraction, the aluminium dissolves as sodium aluminate and the residue is separated by
filtering. The aluminium compounds are precipitated (to get the solid substance from a liquid) when
the liquid is cooled and then ‘seeded’ with fine-grained aluminium hydroxide crystals in a reaction
that takes several days.
Aluminium metal is extracted through smelting using further electrolysis after dissolving the
aluminium oxide, which was obtained from the Bayer’s Process, in molten cryolite. This salt bath is
electrolyzed in a purpose-built cell – and this last step is called the Hall-Heroult process.
The exact mineralogy of Bauxite is important to know to dictate the refining condition which would
determine the most efficient procedures for obtaining the extract.
MSK adopted the p-XRD method which enables accurate quantitative estimation of all the phases
(THA, MHA, available Alumina, etc.) present in the mineral.