Efficient separation of vanadium, titanium, and iron from vanadium-bearing titanomagnetite by pressurized pyrolysis of ammonium chloride-acid leaching-solvent extraction process

A novel process featuring pressurized pyrolysis of ammonium chloride-acid leaching-solvent extraction was carried out to separate vanadium, titanium, and iron from vanadium-bearing titanomagnetite (VBT). Then vanadium and iron existed in the form of ammonium polyvanadate ((NH 4 ) 2 V 6 O 16 ) and ammonium jarosite (NH 4 Fe 3 (SO 4 ) 2 (OH) 6 ) after precipitation from the water phase and the raffinate, while titanium remained in the acid leaching tailings. When pyrolysis temperature of 320 °C, pyrolysis time of 2 h, and the mass ratio of NH 4 Cl to slag of 1.5 followed by leaching in 61.7 g/L HCl solution, the extraction rates of vanadium, titanium, and iron reached 95.1%, 1.2%, and 92.5%, respectively. The analysis through XRD and SEM-EDS proves that the main phases of the roasted sample were attributed to FeCl 2 and FeCl 3, indicating pressurized pyrolysis of ammonium chloride could promote the capture of more vanadium by generated ferric/ferrous chloride in situ. The concentration of vanadium and iron was enriched to 17.8 g/L and 10.6 g/L through the N 235 solvent extraction-Na 2 SO 4 washing-Na 2 CO 3 stripping processes, which could produce V 2 O 5 with a purity of 99.93% by roasting (NH 4 ) 2 V 6 O 16 and ammonium jarosite with excellent crystal faces. Additionally, the TiO 2 concentration reached 184.2 g/L using 80 wt% sulfuric acid for the acid leaching residue, which could be used as the raw material to production of TiO 2 pigment. Moreover, the mechanism of the reaction of NH 4 Cl with valuable metal in the closed environment has been systematically studied.