A computational assessment of the permeability and salt rejection of carbon nanotube membranes and their application to water desalination

Michael Thomas, Ben Corry*

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    101 Citations (Scopus)

    Abstract

    Membranes made from nanomaterials such as nanotubes and graphene have been suggested to have a range of applications in water filtration and desalination, but determining their suitability for these purposes requires an accurate assessment of the properties of these novel materials. In this study, we use molecular dynamics simulations to determine the permeability and salt rejection capabilities for membranes incorporating carbon nanotubes (CNTs) at a range of pore sizes, pressures and concentrations. We include the influence of osmotic gradients and concentration build up and simulate at realistic pressures to improve the reliability of estimated membrane transport properties. We find that salt rejection is highly dependent on the applied hydrostatic pressure, meaning high rejection can be achieved with wider tubes than previously thought; while membrane permeability depends on salt concentration. The ideal size of the CNTs for desalination applications yielding high permeability and high salt rejection is found to be around 1.1nm diameter. While there are limited energy gains to be achieved in using ultra-permeable CNT membranes in desalination by reverse osmosis, such membranes may allow for smaller plants to be built as is required when size or weight must be minimized. There are diminishing returns in further increasing membrane permeability, so efforts should focus on the fabrication of membranes containing narrow or functionalized CNTs that yield the desired rejection or selection properties rather than trying to optimize pore densities.

    Original languageEnglish
    Article number20150020
    JournalPhilosophical transactions. Series A, Mathematical, physical, and engineering sciences
    Volume374
    Issue number2060
    DOIs
    Publication statusPublished - 13 Feb 2016

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