Separation of adjacent heavy rare earth Lutetium (III) and Ytterbium (III) by task-specific ionic liquid Cyphos IL 104 embedded polymer inclusion membrane

Adjacent rare earth separation has always been one of the hardest separation tasks around world. In this article, a task-specific ionic liquid Cyphos IL 104 embedded polymer inclusion membrane (PIM) was fabricated to realize the adsorption and separation of adjacent heavy rare earth elements Lutetium (III) and Ytterbium (III). Chemical composition of the PIM was verified by attenuated total reflectance Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy. And results confirmed only P[dbnd]O and P–O groups participated in the formation of Rare Earth (III)-Cyphos IL 104 complex. A typical thumb-like asymmetric structure was observed by scanning electron microscopy. And the addition of Cyphos IL 104 promoted the hydrophilicity of the PIM as the water contact angle became smaller. Static adsorption and dynamic transport performances were studied in details to get the optimum separation condition. The permeability coefficients of Yb(III) and Lu(III) were 156 μm s⁻¹ and 114.82 μm s⁻¹, respectively; And the initial membrane fluxes were 90.17 μm m⁻² s⁻¹ and 65.61 μm m⁻² s⁻¹, respectively. The separation factor between Yb(III) and Lu(III) was calculated as 1.37 under the optimized transport condition. All these would provide promising developments of adjacent heavy rare earth separation with an efficient and practical membrane strategy.