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 ((NH4)2V6O16) and ammonium jarosite (NH4Fe3(SO4)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 NH4Cl 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 FeCl2 and FeCl3, 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 N235 solvent extraction-Na2SO4 washing-Na2CO3 stripping processes, which could produce V2O5 with a purity of 99.93% by roasting (NH4)2V6O16 and ammonium jarosite with excellent crystal faces. Additionally, the TiO2 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 TiO2 pigment. Moreover, the mechanism of the reaction of NH4Cl with valuable metal in the closed environment has been systematically studied.