Experiment and Mechanism Analysis of Dealkalization of Red Mud by Calcium-Based Hydrothermal Leaching

Abstract

Abstract: Red mud is a solid waste residue produced in the process of alumina production, which has caused serious environmental pollution, but due to strong alkalinity, it is difficult to utilize resources. In this paper, hydrothermal leaching of red mud with Ca(OH)₂ as the dealkalization agent was carried out. The effects of the Ca(OH)₂ dosage, reaction temperature and liquid-solid ratio on the dealkalization rate were investigated. Meanwhile, the mechanim and leaching kinetics of the dealkalization process of red mud were analyzed. The results show that the dealkalization rate of red mud reaches 96.3% under the conditions of the Ca(OH)₂ dosage of 60% (mass fraction), reaction temperature of 250 ℃, liquid-solid ratio of 8 mL/g. Ca(OH)₂ effectively removes free alkali and structural alkali from red mud. The cancrinite and katoite in the red mud are decomposed. New phase andradite(hydrated) in the dealkalized residue is the main diffraction peak. Meanwhile, the diffraction peak of hematite is obviously weakened and the diffraction of calcite is enhanced. The leaching process is controlled by the key steps of diffusion in the solid film. The linear correlation coefficients are all greater than 0.97, the characteristic constant is n<1, and the apparent activation energy is 5.20 kJ/mol.

Key words: Ca(OH)₂, red mud, resource utilization, dealkalization, leaching, kinetics, apparent activation energy

CLC Number:

X758

WANG Tao, LI Wang, ZHU Xiaobo, YAN Xudong. Experiment and Mechanism Analysis of Dealkalization of Red Mud by Calcium-Based Hydrothermal Leaching[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(7): 2368-2375.

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