Letter

Tunable sieving of ions using graphene oxide membranes

Received:
Accepted:
Published online:

Abstract

Graphene oxide membranes show exceptional molecular permeation properties, with promise for many applications1,2,3,4,5. However, their use in ion sieving and desalination technologies is limited by a permeation cutoff of 9 Å (ref. 4), which is larger than the diameters of hydrated ions of common salts4,6. The cutoff is determined by the interlayer spacing (d) of 13.5 Å, typical for graphene oxide laminates that swell in water2,4. Achieving smaller d for the laminates immersed in water has proved to be a challenge. Here, we describe how to control d by physical confinement and achieve accurate and tunable ion sieving. Membranes with d from 9.8 Å to 6.4 Å are demonstrated, providing a sieve size smaller than the diameters of hydrated ions. In this regime, ion permeation is found to be thermally activated with energy barriers of 10–100 kJ mol–1 depending on d. Importantly, permeation rates decrease exponentially with decreasing sieve size but water transport is weakly affected (by a factor of <2). The latter is attributed to a low barrier for the entry of water molecules and large slip lengths inside graphene capillaries. Building on these findings, we demonstrate a simple scalable method to obtain graphene-based membranes with limited swelling, which exhibit 97% rejection for NaCl.

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Acknowledgements

This work was supported by the Royal Society and the Engineering and Physical Sciences Research Council, UK (EP/K016946/1 and EP/M506436/1). K.G. acknowledges Marie Curie International Incoming Fellowship. K.S.V. and R.R.N. acknowledge support from BGT Materials Limited.

Author information

Author notes

    • Jijo Abraham
    •  & Kalangi S. Vasu

    These authors contributed equally to this work

Affiliations

  1. National Graphene Institute, University of Manchester, Manchester M13 9PL, UK

    • Jijo Abraham
    • , Kalangi S. Vasu
    • , Yang Su
    • , Christie T. Cherian
    • , Irina V. Grigorieva
    •  & Rahul R. Nair
  2. School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK

    • Jijo Abraham
    • , Kalangi S. Vasu
    • , Christopher D. Williams
    • , Yang Su
    • , Christie T. Cherian
    • , James Dix
    • , Paola Carbone
    •  & Rahul R. Nair
  3. School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK

    • Jijo Abraham
    • , Kalon Gopinadhan
    •  & Andre K. Geim
  4. School of Materials, University of Manchester, Manchester M13 9PL, UK

    • Eric Prestat
    •  & Sarah J. Haigh

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Contributions

R.R.N. designed and supervised the project with J.A. and K.S.V.; J.A. and K.S.V. prepared the samples, performed the measurements and carried out the analysis with help from R.R.N.; J.D., C.D.W. and P.C. carried out MD simulations and data analysis. K.G., Y.S. and C.T.C. helped in sample preparation, characterization and data analysis. E.P. and S.J.H. contributed to sample characterization. A.K.G. participated in discussions and project design. R.R.N., K.S.V., J.A., C.D.W., I.V.G. and A.K.G. wrote the manuscript. All authors contributed to discussions.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Rahul R. Nair.

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