Zhang Xiao, Xue Xilong, Ding Dexin, Gu Yuantong, Sun Pengcheng
Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, Hunan, China; School of Resources, Environment and Safety Engineering, University of South China, Hengyang 421001, Hunan, China.
School of Resources, Environment and Safety Engineering, University of South China, Hengyang 421001, Hunan, China; State Key Laboratory for Comprehensive Utilization of Nickel and Cobalt Resources, Jinchuan Group Co., Ltd., Jinchang 737100, Gansu, China.
Sci Total Environ. 2023 Mar 10;863:160863. doi: 10.1016/j.scitotenv.2022.160863. Epub 2022 Dec 10.
Surface storage of uranium tailings presents a potential threat to the environment and human health. Cemented backfill can be used to dispose of tailings and control the ground pressure of stopes, providing a new approach for the in-situ seal of heap leaching uranium tailings (HLUTs). The backfilling characteristics of HLUTs were investigated by analyzing the release mechanism of sulfuric acid in HLUTs, the rheological properties of backfill slurry, as well as the strength development and microscopic characteristics of cemented HLUTs backfill (CUTB). The environmental effects of the CUTB were also assessed, and a novel filling process was presented. The results showed that the release rate of sulfuric acid in HLUTs decreased logarithmically, and the content of free sulfuric acid in coarse particles surfaces and ultrafine particles is high, which can be pretreated with 0.1 % quicklime. Slurry with a mass concentration of 74 % ~ 76 % can satisfy the requirements for pipeline transport. The CUTB's strength raised quickly in the former 90d, then decreased to a different extent after 150d, adding 50 wt% FA can enhance its later stability. The leaching level of uranium in CUTB cured for 28d is below the stipulated limit (GB 23727-2009) under different test conditions, having little impact on the underground environment. The hydration products of CUTB are mainly gypsum and C-S-H gel. Gypsum causes later degradation in strength; numerous C-S-H gels generated by the secondary hydration of FA enhance the resistance to sulfate corrosion. These findings have demonstrated that cemented backfill has a high inclusion ratio and low cost for HLUTs, which is of great significance to the HLUTs minimization and the safety of mining while promoting the environmentally friendly development of uranium mines and mills.
铀尾矿的地表堆存对环境和人类健康构成潜在威胁。胶结充填可用于处置尾矿并控制采场的地压，为堆浸铀尾矿的原位密封提供了一种新方法。通过分析铀尾矿中硫酸的释放机理、充填料浆的流变特性以及胶结铀尾矿充填体（CUTB）的强度发展和微观特性，研究了铀尾矿的充填特性。还评估了CUTB的环境影响，并提出了一种新型充填工艺。结果表明，铀尾矿中硫酸的释放速率呈对数下降，粗颗粒表面和超细颗粒中的游离硫酸含量较高，可用0.1%的生石灰进行预处理。质量浓度为74%~76%的料浆可满足管道输送要求。CUTB的强度在前90天内迅速提高，150天后不同程度下降，添加50 wt%的粉煤灰可提高其后期稳定性。在不同试验条件下，养护28天的CUTB中铀的浸出水平低于规定限值（GB 23727-2009），对地下环境影响较小。CUTB的水化产物主要为石膏和C-S-H凝胶。石膏导致后期强度退化；粉煤灰二次水化生成的大量C-S-H凝胶增强了抗硫酸盐侵蚀能力。这些研究结果表明，胶结充填对铀尾矿具有高包容率和低成本，对铀尾矿的减量化和采矿安全具有重要意义，同时促进了铀矿山和选矿厂的绿色发展。
