Mechanism of synthesis of anatase TiO2pigment from low concentration of titanyl sulfuric–chloric acid solution under hydrothermal hydrolysis

Synthesis of dual-modified Fe-doped and carbon-coated Li4Ti5O12 anode based on industrial H2TiO3 for Li-ion batteries

Spinel Li4Ti5O12 (LTO) is a promising candidate for lithium-ion battery anodes because of its exceptional stability and safety. However, its extensive application is limited by a high comprehensive cost, poor electronic conductivity, and other inherent defects. This work presents a novel synthesis procedure to synthesize carbon-coated Fe-doped LTO composites through carbon reduction, in the presence of Fe-containing industrial H2TiO3 as the titanium source, and glucose as the carbon source. The presence of the Fe-dopant is confirmed through XRD, with Rietveld refinement and EDS experiments. Results show that Fe2+ replaces a portion of Ti4+ after doping, leading to an increase in the LTO cell parameters and the corresponding cell volume. FLTO/C, presents a capacity of 153.79 mAh g-1 at 10 C, and the capacity decay per cycle is only 0.0074% after 1000 cycles at 5 C. Moreover, EIS experiments indicate that the incorporation of Fe and carbon lowers the charge transfer resistance and improves the diffusion and migration of Li+. Notably, since this preparation process requires no additional Fe source as a raw material, it is simple, cost-effective, and suitable for large-scale production and further application.

Preparation of Hydrated TiO2 Particles by Hydrothermal Hydrolysis of Mg/Al-Bearing TiOSO4 Solution

As the byproduct in the smelting process of vanadium titano-magnetite, titanium-bearing blast furnace slag (TBFS) can be converted to a titanyl sulfate (TiOSO₄) solution containing MgSO₄ and Al₂(SO₄)₃ impurities via dissociation by concentrated H₂SO₄ (80-95%) at 80-200 °C, followed by leaching with H₂O at 60-85 °C. In this study, hydrated TiO₂ was prepared by hydrothermal hydrolysis of a Mg/Al-bearing TiOSO₄ solution at 120 °C and the hydrolysis law was investigated. The experimental results indicate that MgSO₄ and Al₂(SO₄)₃ accelerated the hydrolysis and significantly affected the particle size (increasing the primary agglomerate size from 40 to 140 nm) and dispersion (reducing the aggregate size from 12.4 to 1.5 μm) of hydrated TiO₂. A thermodynamic equilibrium calculation showed TiOSO₄ existed as TiO²⁺ and SO₄^2- in the solution, and MgSO₄ and Al₂(SO₄)₃ led to little change of [TiO²⁺], but an obvious decrease of [H⁺], which favored the hydrolysis process. At the same time, the coordination-dissociation mechanism of SO₄^2- and Al(SO₄)₂^- facilitated the lap bonding of Ti-O-Ti, promoting the growth of hydrated TiO₂ synergistically.

Recovery of tungsten and titanium from spent SCR catalyst by sulfuric acid leaching process

The widespread use of selective catalytic reduction (SCR) catalysts has resulted in a large accumulation of spent SCR catalysts. These spent catalysts present a significant risk of environmental hazards and potential for resource recovery. This paper presents a feasible process, which works using atmospheric pressure leaching, of tungsten and titanium recovery from spent SCR catalysts. In this new method, titanium and tungsten are simultaneously leached with sulfuric acid as the leaching agent. After hydrolysis and calcination, titanium-tungsten powder with low impurity and reconstructed pore properties was obtained. The optimal conditions for the leaching of Ti and W were as follows: temperature, 150 °C; reaction time, 60 min; H₂SO₄ concentration, 80 %; mass ratio of H₂SO₄/TiO₂, 3:1; and diluted H₂SO₄ concentration, 20 % after reaction. With these optimum conditions, the leaching efficiency of Ti and W were found to be 95.92 % and 93.83 %, respectively. The ion speciation and reaction mechanism of W were studied by Raman spectroscopy, FTIR, and UV-vis. The formation of heteropolytungstate with a Keggin structure is essential for the synergistic leaching of Ti and W, as the heteropolytungstate can be stably dissolved in the acid solution. During the hydrolysis process, heteropolytungstate gradually decomposed into Ti⁴⁺ and WO₄^2- due to the formation of insoluble Ti(OH)₄ from Ti⁴⁺ in the solution. This study demonstrated an effective method for synergistic recovery of titanium and tungsten from the spent SCR catalyst.

Effects of Structural Factors of Hydrated TiO2 on Rutile TiO2 Pigment Preparation via Short Sulfate Process

The structural factors such as crystal structure, particle size distribution and impurity content of hydrated TiO₂ had great effects on the structures and pigment properties of the rutile TiO₂. The rutile TiO₂ white pigment was prepared via the Short Sulfate Process from low concentration industrial TiOSO₄ solution. In order to produce rutile TiO₂ pigment with good structures and excellent pigment properties, the crystal size of the hydrated TiO₂ should be controlled less than 8.9 nm and as close as possible to 7.9 nm, which could effectively promote the phase transformation and crystal growth of the rutile TiO₂. The appropriate particle size distribution of hydrated TiO₂ had obvious effects on obtaining rutile TiO₂ with narrower particle size distribution and near 0.20 µm. It was best to adjust the hydrolysis conditions to reduce the specific surface area of the hydrated TiO₂ so as to reduce the iron ion impurity adsorption.