Natisite (Na₂TiSiO₅) is a layered sodium titanosilicate containing TiO₅ square pyramids. The structure evolution of natisite in water and acid solutions is the basis for its potential applications. With Na₂SiO₃ as the silicon source, natisite with the shape of the square sheet was selectively prepared from the hydrothermal method with 14.3 mol/L NaOH solution at 240 °C. Natisite has 20 Raman active modes and 22 infrared active modes from the first-principles calculations within density functional theory, and the calculated Raman and infrared spectra agree well with the experimental ones. The characteristic Raman peak at 844 cm⁻¹ is caused by the symmetric stretching of the apical Ti–O bond in the TiO₅ unit, assigning to A_1g and B_2g modes. Natisite remains relatively stable in water with a sodium leaching percentage of lower than 6%. When washing with sulfuric acid solutions, the interlayer spacing of natisite is reduced due to the extensive removal of sodium ions, and an intermediate composed of SiO₄ and newly formed TiO₆ units may be formed. Moreover, after washing with water and acid solutions, 95.5%, 63.4%, and 35.2% of Na, Si, and Ti in natisite can be leached in total, respectively, resulting in the structural disintegration of natisite.

The sodium smelting of vanadium–titanium magnetite (VTM) can realize a multi-component comprehensive utilization of VTM. To broaden the application of the vanadium-bearing pig iron produced through this process, it is imperative to maintain the titanium content in molten iron at a very low level. In this study, the effects of temperature, the added amounts of sodium carbonate and anthracite, and the smelting time on the titanium content of molten iron were investigated using thermodynamic calculations and experiments. The results indicate that the introduction of sodium carbonate makes the reduction reaction of VTM a relatively low-temperature smelting system. In the smelting process, the Ti content in molten iron increases with the increase in temperature and decreases with the addition of sodium carbonate, while the amount of anthracite added has little effect on it. The appropriate technological parameters were determined as temperature: 1150–1250 °C, smelting time: ≥2 h, anthracite consumption: 25–35%, and sodium carbonate consumption: ≥60%. In addition, it was determined that the Ti impurities in the V-bearing pig iron were mainly (Ti,V)(C,N), CaTiO₃, and Na₂TiO₃. All results obtained from this work contribute to the comprehensive utilization of VTM, and also provide theoretical support for the sodium smelting of VTM.

V-bearing molten iron was obtained by adding Na₂CO₃ in the smelting process of vanadium titanomagnetite at low temperature. Two forms of V-rich carbides ((Fe,V)₃C, VC) were detected in the V-bearing pig iron products. Once the smelting temperature was above 1300 °C, most of the V in the raw ore was reduced into molten iron. Owning to the high content of V, the unsteady (Fe,V)₃C solid solution decomposed along with the precipitation of graphite and VC during the solidification process. The presence of VC cluster and VC precursor in (Fe,V)₃C was detected by transmission electron microscopy, which confirmed the possibility of this transition process at the atomic perspective. The transformation dramatically affected the compositions and properties of V-bearing pig iron and had important guiding significance for the actual production process.