Electrochemical recovery of Nd using liquid metals (Bi and Sn) in LiCl-KCl-NdCl3
Electrochemical recovery of Nd using liquid metals (Bi and Sn) in LiCl-KCl-NdCl3
复制标题
DOI：
10.1016/j.electacta.2022.140655
复制
发表时间：
2022-05
影响因子：
6.6
通讯作者：
Sang-Moo Im;N. Smith;Stephanie Castro Baldivieso;Jarrod Gesualdi;Ziming Liu;Hojong Kim
中科院分区：
文献类型：
--
作者：
Sang-Moo Im;N. Smith;Stephanie Castro Baldivieso;Jarrod Gesualdi;Ziming Liu;Hojong Kim
利用Nd与液态金属的强相互作用，在773 ~ 973 K的熔融licl - kcl - ndcl3电解液中实现了Nd向Bi和Sn液态金属的高效回收。根据Nd-Sn和Nd-Bi合金的电动势测量，确定Nd在973 K时的活度值低至1.1-5.8×10-13in， Nd在Sn中的溶解度为1.46 mol%，在Bi中的溶解度为5.65 mol%。在10-50 mA cm - 2的沉积-去除循环中，两种液态金属都表现出高的往返库仑效率（>99.3%），并且在超过溶解度极限的情况下，回收能力高达约20 mol% Nd。此外，基于873-973 K恒流电解（-50 mA cm-2）后Bi电解产物的化学分析，证实了相对于外加电荷的Nd回收率高（84-90%）。基于电流-电位曲线和电化学阻抗谱分析，发现沉积过程中的过电位来源于电荷传递电阻和传质电阻。在~ 220 mA cm-2的高交换电流密度下，Nd沉积到液态金属中的电荷转移动力学很容易。熔融氯化物中Nd的高回收率被认为是由于液态金属中Nd的强化学相互作用（即低活性），通过有效抑制多价态（Nd2+和Nd3+）的副反应途径，促进一步还原，即Nd3++ 3e→Nd（在Bi或Sn中）。
Highly efficient recovery of Nd into liquid metals of Bi and Sn was achieved in molten LiCl-KCl-NdCl3electrolyte at 773–973 K by leveraging the strong interactions of Nd with liquid metals. Based on the emf measurements of Nd-Sn and Nd-Bi alloys, the activity values of Nd were determined as low as 1.1‒5.8×10–13in both liquid metals at 973 K while the solubility of Nd was found to be 1.46 mol% in Sn and 5.65 mol% in Bi. Both liquid metals demonstrated high round-trip coulombic efficiencies (>99.3%) during deposition-removal cycles of 10‒50 mA cm‒2and high recovery capacity up to approximately 20 mol% Nd beyond the solubility limit. In addition, a high Nd recovery yield (84–90%) with respect to the applied charge was confirmed based on chemical analysis of electrolysis products in Bi after constant current electrolysis (–50 mA cm–2) at 873‒973 K. Overpotentials during the Nd deposition process were attributed to charge-transfer and mass-transport resistances based on the current-potential curve and electrochemical impedance spectroscopy. The charge-transfer kinetics of Nd deposition into liquid metals was facile with high exchange current densities at ∼220 mA cm‒2. The exceptionally high recovery efficiency for Nd in the molten chloride is thought to result from strong chemical interactions (i.e., low activity) of Nd in liquid metals that encourage one-step reduction, i.e., Nd3++ 3e → Nd(in Bi or Sn) by effectively suppressing side reaction pathways from multivalent states (Nd2+and Nd3+).