Selective ion separations are increasingly needed to combat water scarcity, recover resources from wastewater, and enable the efficient recycling of electronics waste. Emulsion liquid membranes (ELMs) have received interest due to rapid kinetics, high selectivities, and low solvent requirements but are too unstable for industrial usage. We demonstrate that polymeric microcapsules can serve as robust, solvent-free mimics of ELMs. As a proof of concept, we incorporated the copper-selective ligand Lix 84-I in the walls of microcapsules formed from a commercial polystyrene-b-polybutadiene-b-polystyrene triblock polymer. The microcapsules were formed from a double-emulsion template, resulting in particles typically 20–120 μm in diameter that encapsulated even smaller droplets of a dilute (≤0.5 M) H₂SO₄ solution. Batch experiments demonstrated facilitated-transport behavior, with equilibrium reached in as little as 10 min for microcapsules with 1% ligand, and with ∼15-fold selectivity for Cu²⁺ over Ni²⁺. Furthermore, the microcapsules could be packed readily in columns for flow-through operation, thus enabling near-complete Cu²⁺ removal in ∼2 min under certain conditions, recovery of Cu²⁺ by flowing through fresh dilute H₂SO₄, and reuse for at least 10 cycles. The approach in this work can serve as a template for using selective ligands to enable robust and simple flow-through processes for a variety of selective ion separations.

中文翻译：

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聚合物微胶囊作为用于选择性离子分离的乳液液膜的稳健模拟物

越来越需要选择性离子分离来应对水资源短缺、从废水中回收资源以及实现电子废物的有效回收。乳液液膜 (ELM) 因其快速动力学、高选择性和低溶剂需求而受到关注，但对于工业应用来说太不稳定。我们证明聚合物微胶囊可以作为 ELM 的坚固、无溶剂模拟物。作为概念证明，我们将铜选择性配体 Lix 84-I 掺入由商用聚苯乙烯-b-聚丁二烯-b形成的微胶囊壁中-聚苯乙烯三嵌段聚合物。微胶囊由双乳液模板形成，产生的颗粒通常直径为 20–120 μm，其中封装了更小的稀释 (≤0.5 M) H ₂ SO ₄溶液液滴。批次实验证明了促进运输行为，对于具有 1% 配体的微胶囊，在短短 10 分钟内达到平衡，并且对 Cu ²⁺的选择性比 Ni ²⁺高约 15 倍。此外，微胶囊可以很容易地装在柱子中进行流通操作，从而在特定条件下能够在约 2 分钟内几乎完全去除 Cu ²⁺，通过流过新鲜的稀 H ₂ SO _{4回收 Cu} ²⁺, 并重复使用至少 10 个周期。这项工作中的方法可以作为使用选择性配体的模板，为各种选择性离子分离实现稳健而简单的流通过程。