Wilfong Walter C, Ji Tuo, Duan Yuhua, Shi Fan, Wang Qiuming, Gray McMahan L
National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236-0940, USA; NETL Support Contractor, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236-0940, USA.
National Energy Technology Laboratory, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236-0940, USA; NETL Support Contractor, 626 Cochrans Mill Road, P.O. Box 10940, Pittsburgh, PA 15236-0940, USA.
J Hazard Mater. 2022 Feb 15;424(Pt C):127625. doi: 10.1016/j.jhazmat.2021.127625. Epub 2021 Oct 30.
The ubiquitous and growing global reliance on rare earth elements (REEs) for modern technology and the need for reliable domestic sources underscore the rising trend in REE-related research. Adsorption-based methods for REE recovery from liquid waste sources are well-positioned to compete with those of solvent extraction, both because of their expected lower negative environmental impact and simpler process operations. Functionalized silica represents a rising category of low cost and stable sorbents for heavy metal and REE recovery. These materials have collectively achieved high capacity and/or high selective removal of REEs from ideal solutions and synthetic or real coal wastewater and other leachate sources. These sorbents are competitive with conventional materials, such as ion exchange resins, activated carbon; and novel polymeric materials like ion-imprinted particles and metal organic frameworks (MOFs). This critical review first presents a data mining analysis for rare earth element recovery publications indexed in Web of science, highlighting changes in REE recovery research foci and confirming the sharply growing interest in functionalized silica sorbents. A detailed examination of sorbent formulation and operation strategies to selectively separate heavy (HREE), middle (MREE), and light (LREE) REEs from the aqueous sources is presented. Selectivity values for sorbents were largely calculated from available figure data and gauged the success of the associated strategies, primarily: (1) silane-grafted ligands, (2) impregnated ligands, and (3) bottom-up ligand/silica hybrids. These were often accompanied by successful co-strategies, especially bite angle control, site saturation, and selective REE elution. Recognizing the need to remove competing fouling metals to achieve purified REE "baskets," we highlight techniques for eliminating these species from acid mine drainage (AMD) and suggest a novel adsorption-based process for purified REE extraction that could be adapted to different water systems.
现代技术对稀土元素（REEs）的全球普遍且不断增长的依赖，以及对可靠国内资源的需求，凸显了与稀土元素相关研究的上升趋势。基于吸附的从液体废物源中回收稀土元素的方法因预期较低的负面环境影响和更简单的工艺操作，而具备与溶剂萃取法竞争的优势。功能化二氧化硅是一类新兴的低成本且稳定的吸附剂，用于重金属和稀土元素的回收。这些材料总体上已实现从理想溶液、合成或实际煤废水及其他渗滤液源中高效且/或高选择性地去除稀土元素。这些吸附剂可与传统材料（如离子交换树脂、活性炭）以及新型聚合材料（如离子印迹颗粒和金属有机框架（MOFs））相竞争。这篇综述首先对科学网索引的稀土元素回收出版物进行了数据挖掘分析，突出了稀土元素回收研究重点的变化，并证实了对功能化二氧化硅吸附剂的兴趣急剧增长。文中详细考察了从水源中选择性分离重稀土（HREE）、中稀土（MREE）和轻稀土（LREE）的吸附剂配方及操作策略。吸附剂的选择性值主要根据现有数据计算得出，并衡量相关策略（主要包括：（1）硅烷接枝配体，（2）浸渍配体，（3）自下而上的配体/二氧化硅杂化材料）的成功程度。这些策略通常还伴随着成功的协同策略，特别是咬角控制、位点饱和及选择性稀土元素洗脱。认识到需要去除竞争性的污染金属以获得纯化的稀土元素“组合”，我们强调了从酸性矿山排水（AMD）中去除这些物质的技术，并提出了一种基于吸附的纯化稀土元素提取新工艺，该工艺可适用于不同的水系统。
