The development of an efficient recycling route for spent polymer electrolyte membrane (PEM) electrolyzers is essential for the recovery of platinum-group metals (PGMs). Among the other refining processes, solvent extraction is a highly selective technique that can provide high-purity products. Moreover, the extraction behavior of Pt, Ru, and Ir from the PEM electrocatalysts is not studied extensively. In this work, the effect of extraction conditions for the efficient recovery of PGMs from model solutions was investigated. To determine the efficiency of extraction and stripping processes, metal contents in the feed solution, raffinate, and loaded strip solutions were quantified using inductively coupled plasma optical emission spectroscopy (ICP-OES). For achieving high separation efficiencies for Pt and Ru from Ir, the following conditions were found to be optimal: 100 mg/L of each PGM in 2 M HCl, 15 vol.-% Cyanex 923 in diesel, an organic to aqueous volume ratio (O:A) of 1:1, 30 min of stirring time, a temperature of 25 °C, and 400 rpm stirring rate. A short mixing time of 5 min resulted in a high separation factor of Pt/Ir. Stepwise recovery of PGMs from the organic phase was studied. The three-step stripping strategy was proposed to extract PGMs: 1) the separation of Pt and Ir in the aqueous phase using water, 2) the stripping of Ru using a mixture of ascorbic acid and HCl, and 3) the effective stripping of the remaining Pt using water. Furthermore, the separation of PGMs from the leach solution of the spent PEM electrocatalyst with other metal ions (Sb and Sn) was investigated.

中文翻译：

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使用 Cyanex 923 在氯化物介质中溶剂萃取 Pt、Ru 和 Ir，开发废聚合物电解质膜 (PEM) 电解槽的回收路线


开发废聚合物电解质膜（PEM）电解槽的有效回收路线对于铂族金属（PGM）的回收至关重要。在其他精炼工艺中，溶剂萃取是一种高选择性技术，可以提供高纯度的产品。此外，PEM 电催化剂中 Pt、Ru 和 Ir 的萃取行为尚未得到广泛研究。在这项工作中，研究了提取条件对从模型溶液中有效回收铂族金属的影响。为了确定萃取和反萃过程的效率，使用电感耦合等离子体发射光谱 (ICP-OES) 对进料溶液、萃余液和负载反萃溶液中的金属含量进行定量。为了从 Ir 中实现 Pt 和 Ru 的高分离效率，我们发现以下条件是最佳条件：2 M HCl 中每种 PGM 浓度为 100 mg/L，柴油中浓度为 15 vol.-% Cyanex 923，有机物与水的体积比（ O:A) 为 1:1，搅拌时间 30 分钟，温度 25 °C，搅拌速率 400 rpm。 5 分钟的短混合时间可实现 Pt/Ir 的高分离因子。研究了从有机相中逐步回收铂族金属。提出了三步反萃策略来提取 PGM：1）用水分离水相中的 Pt 和 Ir，2）使用抗坏血酸和 HCl 的混合物反萃 Ru，3）有效反萃剩余的 Pt 使用水。此外，还研究了从废 PEM 电催化剂的浸出液中分离 PGM 与其他金属离子（Sb 和 Sn）的情况。