Environmental Safety Analysis of Red Mud-Based Cemented Backfill on Groundwater

Shuai Li, Yulin Zhang, Ru Feng, Haoxuan Yu, Jilong Pan and Jiwei Bian
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Shuai Li: School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Yulin Zhang: School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Ru Feng: School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Haoxuan Yu: School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Jilong Pan: School of Resources and Safety Engineering, Central South University, Changsha 410083, China
Jiwei Bian: School of Resources and Safety Engineering, Central South University, Changsha 410083, China

IJERPH, 2021, vol. 18, issue 15, 1-15

Abstract: As one of the main industrial solid wastes, there are a large number of free alkaloids, chemically bound alkaloids, fluoride, and heavy metal ions in Bayer process red mud (BRM), which are difficult to remove and easily pollute groundwater as a result of open storage. In order to realize the large-scale industrial application of BRM as a backfilling aggregate for underground mining and simultaneously avoid polluting groundwater, the material characteristics of BRM were analyzed through physical, mechanical, and chemical composition tests. The optimum cement–sand ratio and solid mass concentration of the backfilling were obtained based on several mixture proportion tests. According to the results of bleeding, soaking, and toxic leaching experiments, the fuzzy comprehensive evaluation method was used to evaluate the environmental impact of BRM on groundwater. The results show that chemically bound alkaloids that remained in BRM reacted with Ca 2+ in PO 42.5 cement, slowed down the solidification speed, and reduced the early strength of red mud-based cemented backfill (RMCB). The hydration products in RMCB, such as AFT and C-S-H gel, had significant encapsulation, solidification, and precipitation inhibition effects on contaminants, which could reduce the contents of inorganic contaminants in soaking water by 26.8% to 93.8% and the leaching of toxic heavy metal ions by 57.1% to 73.3%. As shown by the results of the fuzzy comprehensive evaluation, the degree of pollution of the RMCB in bleeding water belonged to a medium grade ?, while that in the soaking water belonged to a low grade II. The bleeding water was diluted by 50–100 times to reach grade I after flowing into the water sump and could be totally recycled for drilling and backfilling, thus causing negligible effects on the groundwater environment.

Keywords: Bayer process red mud (BRM); red mud-based cemented backfill (RMCB); environmental safety analysis; groundwater environment; fuzzy comprehensive evaluation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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