Alkalinity stabilization behavior of bauxite residue: Ca-driving regulation characteristics of gypsum

Li, X., Guo, Y., Zhu, F., Huang, L., Hartley, W., Li, Y., Kong, X. and Xue, S. (2019) Alkalinity stabilization behavior of bauxite residue: Ca-driving regulation characteristics of gypsum. Journal of Central South University, 26 (2). pp. 383-392.

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Alkaline anions, include CO32–, HCO3–, Al(OH)4–, OH–, continuously released from bauxite residue (BR), will cause a potential disastrous impact on surrounding environment. The composition variation of alkaline anions, alkaline phase transformation pathway, and micro-morphological transition characteristics during the gypsum addition were investigated in an attempt to understand alkalinity stabilization behavior. Results demonstrated that alkaline anions stabilization degree in leachates can reach approximately 96.29%, whilst pH and alkalinity were reduced from 10.47 to 8.15, 47.39 mmol/L to 2 mmol/L, respectively. During the alkalinity stabilization, chemical regulation behavior plays significant role in driving the co-precipitation reaction among the critical alkaline anions (CO32–, HCO3–, Al(OH)4–, OH–), with calcium carbonate (CaCO3)) being the most prevalent among the transformed alkaline phases. In addition, XRD and SEM-EDX analyses of the solid phase revealed that physical immobilization behavior would also influence the stability of soluble alkali and chemical bonded alkali due to released Ca2+ from gypsum which aggregated the clay particles and stabilized them into coarse particles with a blocky structure. These findings will be beneficial for effectively regulating strong alkalinity of BR.

Item Type: Article
Keywords: bauxite residue, gypsum, alkalinity stabilization, phase transformatio, n Ca-driven regulation
Divisions: Crop and Environment Sciences (to 31.07.20)
Depositing User: Ms Kath Osborn
Date Deposited: 25 Apr 2019 15:51
Last Modified: 25 Apr 2019 15:51

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