Microscale spherical TiO2 powder prepared by hydrolysis of TiCl4 solution: Synthesis and kinetics--颗粒学报PARTICUOLOGY

Yan, P., Zhang, Y., & Zheng, S. (2024). Microscale spherical TiO2 powder prepared by hydrolysis of TiCl4 solution: Synthesis and kinetics. Particuology, 84, 60-71. https://doi.org/10.1016/j.partic.2023.03.004

Microscale spherical TiO₂ powder prepared by hydrolysis of TiCl₄ solution: Synthesis and kinetics

Peiyi Yan ^{a b c}, Ying Zhang ^{c d *}, Shili Zheng ^{a b c *}

a School of Rare Earths, University of Science and Technology of China, Hefei, 230026, China
b Ganjiang Innovation Academy, Chinese Academy of Sciences, Ganzhou, 341119, China
c Key Laboratory of Green Process and Engineering, National Engineering Research Center of Green Recycling for Strategic Metal Resources, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China
d State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization, Panzhihua, 617000, China

10.1016/j.partic.2023.03.004

Volume 84, January 2024, Pages 60-71

Received 5 January 2023, Revised 1 March 2023, Accepted 3 March 2023, Available online 21 March 2023, Version of Record 28 March 2023.

E-mail: zhangying@ipe.ac.cn; slzheng@ipe.ac.cn

Highlights

• Flow field, solution compositions, and temperature are key factors for hydrolysis.

• Morphology and powder size of TiO₂ via hydrolyzing TiCl₄ solution can be tuned.

• Cheng and Wunderlich modified Avrami equation are used for the kinetic fitting.

• Reaction rate constant and active nucleus deactivation rate index are involved.

Abstract

Hydrolysis of TiCl₄ solution is capable of preparing microscale TiO₂ particles. This research studied the synthesis of microscale spherical TiO₂ powders and the hydrolysis kinetics. The effects of the flow field generated by different agitators and baffles in the crystallizer, the initial free acid concentration, the initial equivalent TiO₂ concentration, and the temperature on the hydrolysis progress and powder morphology were systematically studied. The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders, and the axial flow can improve the sphericity of the powders. The increased free HCl and equivalent TiO₂ concentrations in the pregnant solution inhibit the forward hydrolysis reaction, prolong the time to reach equilibrium, and reduce the yield. An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size. Powders with sizes ranging from around 5 μm–40 μm can be tuned under controlled flow field, solution compositions, and temperature conditions. In addition, the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling. The effects of the free HCl concentration, equivalent TiO₂ concentration, and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index. Increasing the free HCl and equivalent TiO₂ concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei, thus increasing the final powder size, while increasing the temperature will lead to the opposite results.

Graphical abstract

Keywords

TiCl₄; Hydrolysis; Microscale TiO₂; Spherical; Kinetics

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