TREATMENT OF ALUMINUM PRODUCTION SLAG AIMING AT DESTROYING CYANIDE AND RECOVERING INORGANIC RAW MATERIALS

摘要

The Hall-Heroult process for producing aluminium consists, basically, in alumna dissolution in a molten salts bath, constituted for cryolite and aluminium fluoride, in a steel cell called pot. An electric current that pass through the graphite electrodes releases molten metallic aluminium that is collected in the bottom of the pots. In this technical contribution, it was studied the treatment of the slag from this productive process, aiming at removing and destroying the cyanide generated, as well as to define the routes for the inorganic materials recovery. The results show that it is quite feasible to remove the free cyanide by suspending the slag, properly ground, in water and proceeding, soon after, a solid-liquid separation. The leaching solution, thus obtained, was treated for destroying the free cyanide released and the solid residue treated for separating the basic materials that can return to the electrolytic cells (cryolite - Na_3AlF_6 and alumna - (Al_2O_3)).