Polymer inclusion membrane (PIM) has become a potential alternative in efficient Li separation from brines typically with Mg and Li, due to its exceptional stability and selectivity. However, the practical application of PIMs is still greatly restricted by its slow mass transfer and related unclear transport mechanism. Here, we fabricated an efficient PIM with tributyl phosphate (TBP) along with sodium tetraphenylborate (NaBPh) as carriers and cellulose triacetate (CTA) as a polymer skeleton for highly selective and permeable Li separation from high Mg/Li aqueous solutions, offering an initial flux of 3–20 times higher than other PIMs. With increasing TBP content in the PIM, a nonmonotonical trend (sharp increase-leveling off-slow decrease) of its initial flux was observed. The improvement of the solubility (compatibility) of NaBPh in CTA matrix by introducing TBP was demonstrated by scanning electron microscope (SEM) coupled with X-ray energy dispersive spectroscopy (EDS) images, which was highly consistent with binding energy simulation. X-ray diffraction (XRD) and positron annihilation lifetime spectroscopy (PALS) results verify that moderate TBP content in the PIM could enlarge the distance of polymer chains and enhance the initial flux of PIMs, while excessive TBP can occupy the free volume sites, leading to an adverse effect on the permeability. Our study provides valuable information on the compatibility effect on the mass transfer through the polymer matrix including PIMs, which exhibits prospect in a wide range of applications of metal separation.

中文翻译：

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用于 Li+ 回收的高渗透性和选择性聚合物包合膜及其潜在的增强机制

聚合物包合膜 (PIM) 凭借其卓越的稳定性和选择性，已成为从通常含有镁和锂的盐水中有效分离锂的潜在替代方案。然而，PIMs的实际应用仍然因其缓慢的传质和相关的不清楚的传输机制而受到很大限制。在这里，我们以磷酸三丁酯（TBP）和四苯硼酸钠（NaBPh）为载体，以三醋酸纤维素（CTA）为聚合物骨架，制备了一种高效的 PIM，用于从高 Mg/Li 水溶液中进行高选择性和渗透性的 Li 分离，提供了一种初步的方法。通量比其他 PIM 高 3-20 倍。随着 PIM 中 TBP 含量的增加，观察到其初始通量的非单调趋势（急剧增加-平稳-缓慢减少）。扫描电子显微镜（SEM）结合X射线能谱（EDS）图像证明引入TBP可提高NaBPh在CTA基质中的溶解度（相容性），这与结合能模拟高度一致。 X射线衍射（XRD）和正电子湮灭寿命谱（PALS）结果表明，PIM中适量的TBP含量可以扩大聚合物链的距离，提高PIM的初始通量，而过量的TBP会占据自由体积位点，导致PIM的初始通量增加。对渗透性产生不利影响。我们的研究提供了有关通过包括 PIM 在内的聚合物基质的相容性对传质影响的有价值的信息，这在金属分离的广泛应用中展现了前景。