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 R² more than 0.98. The acid leaching of iron is controlled by surface chemical reaction with R² 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. H 2 C 2 O 4 could selectively destroy the minerals of red mud resulted in the high recovery of vanadium. H 2 C 2 O 4 reacted with Fe²⁺ to generate the precipitation of FeC 2 O 4 in the leaching residue caused by the p-π conjugation of O--C--O of C 2 O 4 ^2-. The stable VO(C 2 O 4) 2 ^2- complex was present in the leaching solution due to the conjugated system of π-π with O--C--O of C 2 O 4 ^2- and V˭O of VO²⁺. Possible selective leaching mechanism of vanadium and iron from red mud with H 2 C 2 O 4. [Display omitted] • Selective leaching of vanadium with H 2 C 2 O 4 and Na 2 SO 3 from red mud was achieved. • Selective leaching process of vanadium and iron was detected by XRD and SEM-EDS. • Leaching behaviors of V and Fe were comparatively investigated by leaching kinetics. • Separation mechanism of V and Fe was analyzed by the solution thermodynamics. [ABSTRACT FROM AUTHOR]