Purification of the Sodium Hydroxide Leaching Solution of Black Dross by Removal of Silicate(IV) with Polyacrylamide (PAM)

ABSTRACT

Black dross contains alumina, metal oxides and nitrides and some salts. In order to recover pure alumina from black dross, a hydrometallurgical process consisting of leaching and solution purification was investigated. Alkaline leaching of mechanically activated black dross resulted in an aluminate solution with 98% purity together with a small amount of silicate. In order to obtain pure aluminate solution, removal of silicate from alkaline leaching liquor was investigated by coagulation with polyacrylamide, which has never been reported. Most of silicate(IV) was removed at the optimum coagulation condition. The strong interaction of silicate(IV) with polyacrylamide was verified through Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectra and viscosity data. The application of this method is expected to have a significant impact on the recovery of pure alumina from black dross materials.