Membrane-based electrodeposition (MED) has emerged as a promising approach for reversible removal-recovery of toxic but valuable Pb2+. However, limited by the low specificity of membrane deposition toward various heavy metal ions in MED, the selective removal of Pb2+ remains an obstacle. Inspired by the soft-hard acid-base theory, here we developed a Pb2+-affinity electroactive membrane by incorporating MoS2 with the cation exchange membrane (CEM) to achieve a tandem Pb2+ selective adsorption-deposition process. CEM@MoS2 achieved nearly 100 % Pb2+ removal selectivity even in the presence of diverse competing cations, with a remarkable distribution coefficient (1.3 × 107 mL·g−1) and treatment capacity (2580.4 mg·g−1), resulting in a high-purity Pb2+ concentrate recovery. Importantly, a spontaneous Mo4+-Pb2+ redox reaction was found, which triggered Pb2+ reduction to metallic Pb. This surficial Pb° formation decreased the energy barrier for subsequent membrane H2O splitting and Pb2+ reduction, accounting for the unexpected self-enhanced Pb2+ removal scenario. Additionally, the exhausted Mo4+ species was facilely regenerated via a cathodic reduction method, demonstrating excellent stability and reusability. The work is expected to provide a viable strategy for selective removal-recovery of heavy metal ions using MED.

中文翻译：

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Mo4+-Pb2+ 氧化还原触发 Pb2+ 的自增强去除和回收，具有超选择性


基于膜的电沉积 （MED） 已成为一种很有前途的可逆去除-回收有毒但有价值的 Pb2+ 的方法。然而，由于 MED 中膜沉积对各种重金属离子的低特异性限制，选择性去除 Pb2+ 仍然是一个障碍。受软硬酸碱理论的启发，我们通过将 MoS2 与阳离子交换膜 （CEM） 结合来实现串联的 Pb2+ 选择性吸附-沉积工艺，开发了一种 Pb2+ 亲和电活性膜。即使在存在多种竞争阳离子的情况下，CEM@MoS2也实现了近 100% 的 Pb2+ 去除选择性，具有显著的分布系数 （1.3 × 107 mL·g−1） 和处理能力 （2580.4 mg·g−1），从而实现了高纯度的 Pb2+ 精矿回收率。重要的是，发现了自发的 Mo4+-Pb2+ 氧化还原反应，该反应触发了 Pb2+ 还原为金属 Pb。这种表面 Pb° 的形成降低了随后膜 H2O 分裂和 Pb2+ 还原的能量屏障，解释了意想不到的自我增强 Pb2+ 去除情况。此外，通过阴极还原法轻松再生耗尽的 Mo4+ 物质，表现出优异的稳定性和可重复使用性。这项工作有望为使用 MED 选择性去除-回收重金属离子提供一种可行的策略。