RECOVERY OF SODA FROM BAUXITE RESIDUE

摘要

A process for recovery of soda from Bayer process bauxite residue comprises the steps: (a) leaching bauxite residue with sulphuric acid to dissolve soda in DSP in bauxite residue therein; (b) neutralizing the slurry of step (a) with caustic materials to precipitate partially dissolved silica, alumina and calcium, and separating the insoluble portion with precipitated materials by filtration to obtain clear liquor of sodium sulphate (c), processing the resulting liquor by membrane electrochemical process to recover caustic soda and sulphuric acid. The caustic soda is returned to the Bayer process and the sulphuric acid is returned to the leaching process. Consequently, the process can be fully integrated with the Bayer process to reduce caustic soda make-up substantially which would be ordinarily lost. Furthermore the characteristics of the leached and neutralized bauxite residue are changed to reduce its hazardous nature and facilitate improved management of the residue disposal area by the use of clean electric power and non-volatile sulphuric acid.