Effects of Reductive Roasting with Sodium Salts on Leaching Behavior of Non-ferrous Elements in Bauxite Ore Residue

摘要

In our previous study, TiO_2 was enriched through stepwise removal of SiO_2 and AI_2O_3 via H_3PO_4 and NaOH leaching from non-magnetic material, which was derived from reductive roasting of bauxite ore residues with sodium salts followed by magnetic separation. In this research, to elucidate the corresponding mechanism, the effects of reductive roasting with sodium salts on leaching behaviors of non-ferrous elements in bauxite ore residues were further investigated. The logC-pH figures have shown the separation between SiO_2 and AI_2O_3 can be achieved through H_3PO_4 leaching, and the leaching results proved the difference of leaching ratio between SiO_2 and AI_2O_3 in bauxite ore residues was promoted from 30 to 60% after reductive roasting with sodium salts under the optimal H_3PO_4 concentration of 1.0 mol/L. TiO_2 was found not dissolved after reductive roasting as the leaching ratio changed from 53.9% to be less than 3%, which was due to the insoluble perovskite (CaTi03) generated in the roasting process. In the NaOH leaching process, the difference between the leaching ratio of AI_2O_3 and SiO_2 in bauxite residue changed from 27.1% to about 60% after reductive roasting under the conditions of maximum AI_2O_3 extraction ratio with 50.wt% NaOH. The above results have indicated that reductive roasting process with sodium salts was not only favorable to the subsequent separation between SiO_2 and AI_2O_3 as well as the enrichment of TiO_2 in H_3PO_4 leaching process, but also beneficial to extraction of AI_2O_3 and the separation between AI_2O_3 and SiO_2 in NaOH leaching process.