Conceptual Process Development for the Separation of Thorium, Uranium, and Rare Earths from Coarse Coal Refuse
Conceptual Process Development for the Separation of Thorium, Uranium, and Rare Earths from Coarse Coal Refuse
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DOI：
10.1080/08827508.2022.2064855
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发表时间：
2022-04
影响因子：
5
通讯作者：
Deniz Talan;Qingqing Huang;Liang Liang-Liang;Xueyan Song
中科院分区：
文献类型：
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作者：
Deniz Talan;Qingqing Huang;Liang Liang-Liang;Xueyan Song
摘要稀土供应链的日益中断使得开发替代资源变得紧迫，其中煤基材料的利用具有巨大潜力。然而，环境控制是稀土提取过程中的一个重大挑战。本研究的目的是提供关于在以煤为基础的产品用作原料时从稀土中去除钍和铀的有限信息。实验室研究表明，选择性沉淀和溶剂萃取法产生最有利的分离性能。在pH值为4.8左右实现完全钍沉淀。由于铀和稀土的沉淀pH范围接近，采用溶剂萃取进一步分离以实现强化分离。基于Box-Behnken实验设计，考察了萃取剂浓度、pH值、反萃剂浓度和O/A比对萃取效果的影响。在pH = 3.5、O/A = 3、H_2SO_4浓度为1 mol/L时，TBP浓度为50 v%时，铀和稀土的萃取率分别为1.8%和73.4%。通过分配比、分离因子、热力学参数和物种分布图进一步评估了元素的萃取和沉淀行为，以提供对分离机制的透彻理解。对结果进行了统计分析，并建立了铀回收率预测模型。开发的实验方案进行了验证，使用中试规模的处理设施生产的稀土草酸盐样品。最后，开发了一个概念性的工艺流程，以有效地分离放射性核素，同时生产稀土氧化物产品。
ABSTRACT Increasing disruption in the rare earth supply chain creates an urgency to develop alternative resources, in which utilization of coal-based materials presents great potential. Nevertheless, environmental control is a significant challenge in rare earth extraction processes. This study was conducted to contribute to the limited information on removing thorium and uranium from rare earths while coal-based products are used as feedstock. The laboratory studies suggested that the selective precipitation and solvent extraction approach yields the most favorable separation performance. Complete thorium precipitation was achieved around a pH value of 4.8. Due to the close precipitation pH ranges of uranium and rare earths, further separation by solvent extraction was applied to achieve an enhanced separation. Based on a Box-Behnken experimental design, the effect of extractant concentration, pH, strippant concentration, and O/A ratio was investigated. Best separation performance was achieved using 50 v% TBP at a pH of 3.5 with an O/A ratio of 3 and 1 mol/L H2SO4, which resulted in 1.8% uranium and 73.4% rare earth extraction. The extraction and precipitation behavior of the elements were further assessed with the distribution ratio, separation factor, thermodynamic parameters, and species distribution diagrams to provide a thorough understanding of the separation mechanisms. The results were statistically analyzed, and a model was developed to predict uranium recovery. The developed experimental protocol was validated using a rare earth oxalate sample produced at the pilot-scale processing facility. Finally, a conceptual process flowsheet was developed to effectively separate radionuclides while producing rare earth oxide products.