Interfacial electroneutrality controls transport of asymmetric salts through charge-patterned mosaic membranes

• 成果类型: Article
• 署名作者: Gao, Feng; Hoffman, John R.; Xu, Jialing; Ievlev, Anton, V; Whitmer, Jonathan K.; Phillip, William A.
• 署名单位: University of Notre Dame; United States Department of Energy (DOE); Oak Ridge National Laboratory; Center for Nanophase Materials Sciences
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-15220
• DOI: 10.1073/pnas.2504069122
• 发表日期: 2025-09-02
• 关键词: copolymer membranes; permeability; selectivity

摘要

Membranes that selectively enhance target solute permeation while rejecting competing species are essential for precision separations. This study introduces charge-patterned mosaic membranes (CMMs) that selectively transport divalent asymmetric salts by leveraging a net-neutral membrane-solution interface. This mechanism, dictated by the charge ratio of positive and negative domains on the membrane surface and the balance of cations and anions in the salt, is supported by analytical, numerical, and experimental results. Analytical solutions identified cationic domain coverages (f+) of 33%, 50%, and 66% as optimal for the selective transport of +2:-1 salts, +1:-1 salts, and +1:-2 salts, respectively, under conditions where the pattern size (L) is significantly larger than the Debye length. Numerical simulations and experiments using CMMs with alternating charged-stripes inkjet-printed onto nanostructure copolymer substrates confirmed these findings. By varying stripe widths to control f+, pressure-driven filtration experiments demonstrated selective enrichment of MgCl2 and K2SO4 at the predicted f+ values, with deviations from these values leading to salt rejection. These results highlight the pivotal role of a net-neutral interface in enabling asymmetric salt enrichment. This study positions CMMs as a versatile platform for tuning ion selectivity, addressing challenges in resource recovery, water treatment, and precision separations.