Selective recovery of vanadium from red mud by leaching with using oxalic acid and sodium sulfite

Selective leaching of vanadium and separation of iron from red mud by using oxalic acid and sodium sulfite were put forward. The main influencing factors of selective leaching were studied and the leaching mechanism was analyzed with XRD, SEM-EDS, thermodynamic theory and leaching kinetics. The results show that more than 90% of vanadium could be selectively leached into the acid solution with less than 10% of iron under the suitable leaching conditions. The acid leaching of vanadium is controlled by boundary layer diffusion with R-2 more than 0.98. The acid leaching of iron is controlled by surface chemical reaction with R-2 more than 0.99 under different oxalic acid concentrations. The apparent activation energy of vanadium and iron was 8.21 kJ/mol and 13.57 kJ/ mol, respectively. H2C2O4 could selectively destroy the minerals of red mud resulted in the high recovery of vanadium. H2C2O4 reacted with Fe2+ to generate the precipitation of FeC2O4 in the leaching residue caused by the p-7C conjugation of O-C-O of C2O42-. The stable VO(C2O4)(2)(2-) complex was present in the leaching solution due to the conjugated system of pi-pi with O-C-O of C2O42- and V=O of VO2+.

Automated summary

Selective leaching of vanadium and separation of iron from red mud using oxalic acid and sodium sulfite were studied, showing that over 90% of vanadium could be selectively leached under suitable conditions. The leaching mechanism was analyzed with XRD, SEM-EDS, thermodynamic theory, and leaching kinetics, demonstrating controlled diffusion and chemical reaction processes for vanadium and iron leaching, respectively. The apparent activation energy of vanadium and iron were determined and the presence of stable complexes in the leaching solution was identified.