The invention relates to a method for producing
aluminium oxide and a by-product
silicon by low-temperature alkali
digestion of low-grade
bauxite, and belongs to the technical field of
aluminium oxide production. The method comprises the following steps: firstly, smashed low-grade diasporic
bauxite and a circulating mother liquid are grinded to form a mineral
slurry; secondly, a
digestion reaction is performed enable
kaolinite in the mineral to be dissolved, react and enter a solution,
filtration residues are high-grade
bauxite concentrate, and the high-grade bauxite concentrate is processed for produce
aluminium oxide and low-alkali
red mud by adopting a
Bayer process;
sodium aluminosilicate in a filtrate is subjected to desilication reaction, so that
sodium-
silicon residues, and a filtrate containing
aluminium oxide,
silicon oxide and
sodium oxide are obtained; and finally, the filtrate is supplemented by
sodium hydroxide, and the supplemented filtrate is used as the circulating mother liquid to return for preparation of the mineral
slurry through
grinding, and part of the sodium-silicon residues are used as a
seed crystal to return to a desilication process, and the other part of the sodium-silicon residues are used to prepare silicon products such as molecular sieves. The method is a whole-procedure wet treatment process, aluminium and
silicone are fully extracted from the bauxite for preparing the corresponding products, also alkali consumption in the
red mud during the
Bayer process is substantially reduced, the alkali content in the
red mud is reduced, and recycle value of the red mud is improved.