ABSTRACT

Temperature-dependency of back-extraction behavior of inert platinum group metals (PGMs) like Ru(III) and Rh(III) has been investigated in a biphasic system consisting of H₂C₂O₄(aq) and betainium bis(trifluoromethylsulfonyl)amide ([Hbet][Tf₂N]) after extracting these PGMs as well as that of non-inert Pd(II). At 298 K, Pd(II) in [Hbet][Tf₂N] phase was stripped high efficiency (78.8%) by 0.1 M H₂C₂O₄ within 2 min. In contrast, back-extraction of Rh(III) and Ru(III) did not proceed at all in practice under the same condition, demonstrating the inertness of these PGMs. When the sample temperature was risen up to 353 K, the stripping of Rh(III) was promoted, and completed within 300 min at 353 K. The stripping efficiency of Ru(III) was still as low as 24.2% at 300 min and 353 K, and took 48 h in use of 1 M H₂C₂O₄(aq) for completion. Further mechanistic studies by means of UV-vis absorption spectroscopy clarified that the complexation of these PGMs and oxalate ion (C₂O₄^2-) is rate-determining in their stripping, and is successfully accelerated and enhanced by elevating the temperature and increasing the concentration of the stripping agent.

摘要

已经在由 H ₂ C ₂ O ₄ (aq) 和甜菜鎓双（三氟甲基磺酰基）组成的双相系统中研究了 Ru(III) 和 Rh(III) 等惰性铂族金属 (PGM) 反萃取行为的温度依赖性酰胺 ([Hbet][Tf ₂ N]) 在提取这些 PGM 以及非惰性 Pd(II) 之后。在 298 K 时，[Hbet][Tf ₂ N] 相中的Pd(II ) 被 0.1 MH ₂ C ₂ O ₄高效（78.8%）汽提2 分钟内 相反，在相同条件下，Rh(III) 和 Ru(III) 的反萃取在实践中根本没有进行，这证明了这些 PGM 的惰性。当样品温度升至 353 K 时，促进了 Rh(III) 的汽提，并在 353 K 时在 300 min 内完成。 Ru(III) 在 300 min 和 353 时的汽提效率仍低至 24.2% K，使用 1 MH ₂ C ₂ O ₄ (aq)耗时 48 小时完成。借助紫外-可见吸收光谱的进一步机理研究阐明，这些 PGM 与草酸根离子 (C ₂ O ₄ ^2-) 在它们的汽提中是决定速率的，并且通过升高温度和增加汽提剂的浓度成功地加速和增强。