4.8 Article

The Donnan potential revealed

Journal

NATURE COMMUNICATIONS
Volume 13, Issue 1, Pages -

Publisher

NATURE PORTFOLIO
DOI: 10.1038/s41467-022-33592-3

Keywords

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Funding

  1. Center for Materials for Water and Energy Systems (M-WET), an Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Basic Energy Sciences [DE-SC0019272]
  2. DOE Office of Science User Facility [DE-AC02-05CH11231]
  3. Early Career Award in the Condensed Phase and Interfacial Molecular Science Program, in the Chemical Sciences Geosciences and Biosciences Division of the Office of Basic Energy Sciences of the U.S. Department of Energy [DE-AC02-05CH11231]

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Donnan electrical potential, which describes ion distribution between two solutions separated by a permeable membrane, has been directly measured and compared with theoretical models in this study. The results highlight the dependence of the Donnan potential on external salt concentration and counter-ion valence, and show a reasonable agreement with current theoretical models.
Donnan electrical potential is widely adopted to describe ion distribution between two solutions separated by a permeable membrane with implications for many chemical and biological systems. Aydogan Gokturk et al. directly measures this potential for the first time and compare the data with theoretical models. Selective transport of solutes across a membrane is critical for many biological, water treatment and energy conversion and storage systems. When a charged membrane is equilibrated with an electrolyte, an unequal distribution of ions arises between phases, generating the so-called Donnan electrical potential at the solution/membrane interface. The Donnan potential results in the partial exclusion of co-ion, providing the basis of permselectivity. Although there are well-established ways to indirectly estimate the Donnan potential, it has been widely reported that it cannot be measured directly. Here we report the first direct measurement of the Donnan potential of an ion exchange membrane equilibrated with salt solutions. Our results highlight the dependence of the Donnan potential on external salt concentration and counter-ion valence, and show a reasonable agreement with current theoretical models of IEMs, which incorporate ion activity coefficients. By directly measuring the Donnan potential, we eliminate ambiguities that arise from limitations inherent in current models.

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