School of Resources and Safety Engineering, Central South University, Changsha 410083, China.
Int J Environ Res Public Health. 2021 Jul 30;18(15):8094. doi: 10.3390/ijerph18158094.
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 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 Ⅲ, 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.
拜耳法赤泥（BRM）是主要的工业固体废物之一，其中含有大量的游离堿、化学结合堿、氟化物和重金属离子，露天存放时难以去除，容易污染地下水。为了实现 BRM 作为地下采矿回填骨料的大规模工业应用，同时避免污染地下水，通过物理、力学和化学成分测试分析了 BRM 的材料特性。根据几个配合比试验，获得了最佳的水泥-砂比和回填体的固含量。根据泌水、浸泡和毒性浸出试验的结果，采用模糊综合评价法评价了 BRM 对地下水的环境影响。结果表明，BRM 中残留的化学结合堿与 PO 42.5 水泥中的 Ca 反应，减缓了固化速度，降低了赤泥基胶结回填料（RMCB）的早期强度。RMCB 中的水化产物，如 AFT 和 C-S-H 凝胶，对污染物具有显著的包裹、固化和沉淀抑制作用，可将浸泡水中无机污染物的含量降低 26.8%至 93.8%，毒性重金属离子的浸出率降低 57.1%至 73.3%。模糊综合评价结果表明，RMCB 渗出水中的污染程度属于中等 III 级，而浸泡水中的污染程度属于低 II 级。渗出水在流入水仓后稀释 50-100 倍，可达到 I 级，可全部回收用于钻探和回填，对地下水环境影响可忽略不计。
