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

Alkaline anions, include CO 3 2– , HCO 3 – , 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 transiti...

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Bibliographic Details
Published in:Journal of Central South University 2019-02, Vol.26 (2), p.383-392
Main Authors: Li, Xiao-fei, Guo, Yin, Zhu, Feng, Huang, Long-bin, Hartley, William, Li, Yi-wei, Kong, Xiang-feng, Xue, Sheng-guo
Format: Article
Language:English
Subjects:
Alkalinity
Anions
Bauxite
Bayer process
Calcium carbonate
Calcium ions
Chemical bonds
Chemical precipitation
Engineering
Environmental impact
Gypsum
Leachates
Metallic Materials
Organic chemistry
Phase transitions
Solid phases
Stabilization
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Summary:Alkaline anions, include CO 3 2– , HCO 3 – , 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 (CO 3 2– , HCO 3 – , Al(OH) 4 – , OH – ), with calcium carbonate (CaCO 3 )) 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 Ca 2+ 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.
ISSN:2095-2899
2227-5223
DOI:10.1007/s11771-019-4010-1