Suspension calcination and alkali leaching of low-grade high-sulfur bauxite: Desulfurization, mineralogical evolution and desilication

Hong-fei Wu; Jun-qi Li; Chao-yi Chen; Fei-long Xia; Zhen-shan Xie

doi:10.1007/s12613-019-1941-3

Volume 27 Issue 5

May 2020

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Article Navigation > International Journal of Minerals, Metallurgy and Materials > 2020 > 27(5): 602-610

Hong-fei Wu, Jun-qi Li, Chao-yi Chen, Fei-long Xia, and Zhen-shan Xie, Suspension calcination and alkali leaching of low-grade high-sulfur bauxite: Desulfurization, mineralogical evolution and desilication, Int. J. Miner. Metall. Mater., 27(2020), No. 5, pp. 602-610. https://doi.org/10.1007/s12613-019-1941-3

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Hong-fei Wu, Jun-qi Li, Chao-yi Chen, Fei-long Xia, and Zhen-shan Xie, Suspension calcination and alkali leaching of low-grade high-sulfur bauxite: Desulfurization, mineralogical evolution and desilication, Int. J. Miner. Metall. Mater., 27(2020), No. 5, pp. 602-610. https://doi.org/10.1007/s12613-019-1941-3

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Research Article

Suspension calcination and alkali leaching of low-grade high-sulfur bauxite: Desulfurization, mineralogical evolution and desilication

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Corresponding author:
Jun-qi Li E-mail: jqli@gzu.edu.cn
Received: 22 May 2019; Revised: 21 November 2019; Accepted: 25 November 2019; Available online: 30 December 2019

Abstract

Abstract

To enable the utilization of low-grade and high-sulfur bauxite, the suspension calcination was used to remove the sulfur and the activate silica minerals, and the calcinated bauxite was subjected to a desilication process in NaOH solution under atmospheric pressure. The desulfurization and desilication properties and mineralogical evolution were studied by X-ray diffraction, thermogravimetry–differential thermal analysis, scanning electron microscopy, and FactSage methods. The results demonstrate that the suspension calcination method is efficient for sulfur removal: 84.21% of S was removed after calcination at 1000°C for 2 min. During the calcination process, diaspore and pyrite were transferred to α-Al₂O₃, magnetite, and hematite. The phase transformation of pyrite follows the order FeS₂ → Fe₃O₄ → Fe₂O₃, and the iron oxides and silica were converted into iron silicate. In the alkali-soluble desilication process, the optimum condition was an alkali solution concentration of 110 g/L, a reaction time of 20 min, and a reaction temperature of 95°C. The corresponding desilication ratio and alumina loss ratio were 44.9% and 2.4%, respectively, and the alumina-to-silica mass ratio of the concentrate was 7.9. The Al₂O₃·2SiO₂, SiO₂, and Al₂O₃ formed during the calcination process could react with NaOH solution, and their activity decreased in the order of Al₂O₃·2SiO₂, SiO₂, and Al₂O₃.
- low-grade bauxite;
- sulfur;
- suspension calcination;
- alkali-soluble desilication;
- Bayer process

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