Water permeability of nanoporous graphene at realistic pressures for reverse osmosis desalination

Cohen-Tanugi, David; Grossman, Jeffrey C.

doi:10.1063/1.4892638

Cited by 171 publications

(123 citation statements)

References 16 publications

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“…In a follow-on study, we confirmed that NPG retains its ultrahigh water permeability under the realistic pressures employed in RO (10 bar to 100 bar) by showing that the water flux across NPG continues to scale linearly with applied pressure down to this lower pressure range [76]. To this end, we examined the desalination process across NPG under feed pressures as low as 29 bar using much longer MD simulations (see Fig.…”

Section: Proof Of Conceptsupporting

confidence: 61%

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Nanoporous graphene as a reverse osmosis membrane: Recent insights from theory and simulation

2015

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We review recent progress in the computational study of graphene as an RO membrane.• We introduce graphene and current knowledge about its mass transport properties. • We examine six key mechanisms that govern salt rejection in graphene. • Molecular dynamics have played a dominant role in the study of graphene membranes. • We suggest a greater role for quantumlevel simulations and macroscale computation.In this review, we examine the potential and the challenges of designing an ultrathin reverse osmosis (RO) membrane from graphene, focusing on the role of computational methods in designing, understanding, and optimizing the relationship between atomic structure and RO performance. In recent years, graphene has emerged as a promising material for improving the performance of RO. Beginning at the atomic scale and extending to the RO plant scale, we review applications of computational research that have explored the structure, properties and potential performance of nanoporous graphene in the context of RO desalination.

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Section: Proof Of Conceptsupporting

confidence: 61%

Section: Salt Rejectionmentioning

confidence: 99%

Nanoporous graphene as a reverse osmosis membrane: Recent insights from theory and simulation

2015

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“…The initial water flux, measured as the difference in the water columns' height between the chambers filled with salt and deionized water versus time, was ∼70 g m −2 s −1 atm −1 (7 × 10 −15 g s −1 atm −1 per pore, assuming a pore density of 1 × 10 12 cm −2 ) for a membrane with I D /I G ≈ 1. Such a flux is more than two orders of magnitude lower than that predicted using numerical simulations by Cohen-Tanugi and colleagues for different pore geometries (1.7 × 10 −12 g s −1 bar −1 per pore) 28 . The observed osmotic pressure-driven asymmetric water flux unambiguously confirms the semipermeable nature of the plasmatreated graphene membranes, at least for the pore densities used in this experiment (I D /I G ≈ 1, ∼1 × 10 12 cm −2 , membrane conductivity ∼0.2 µS).…”

Section: Water Transport and Salt Rejection Measurementsmentioning

confidence: 66%

Water desalination using nanoporous single-layer graphene

et al. 2015

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By creating nanoscale pores in a layer of graphene, it could be used as an effective separation membrane due to its chemical and mechanical stability, its flexibility and, most importantly, its one-atom thickness. Theoretical studies have indicated that the performance of such membranes should be superior to state-of-the-art polymer-based filtration membranes, and experimental studies have recently begun to explore their potential. Here, we show that single-layer porous graphene can be used as a desalination membrane. Nanometre-sized pores are created in a graphene monolayer using an oxygen plasma etching process, which allows the size of the pores to be tuned. The resulting membranes exhibit a salt rejection rate of nearly 100% and rapid water transport. In particular, water fluxes of up to 10(6) g m(-2) s(-1) at 40 °C were measured using pressure difference as a driving force, while water fluxes measured using osmotic pressure as a driving force did not exceed 70 g m(-2) s(-1) atm(-1).

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“…Aqueous electrolytes and model carbon-based materials have already been investigated by molecular simulation in the context of desalination by reverse osmosis [42][43][44] or for nanofluidic osmotic diodes [45]. Molecular simulation provided insights into the structure and dynamics of water and aqueous electrolytes in carbon nanotubes and nanopores [46][47][48].…”

Section: Introductionmentioning

confidence: 99%

Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models

et al. 2018

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Capacitive mixing (CapMix) and capacitive deionization (CDI) are currently developed as alternatives to membrane-based processes to harvest blue energy-from salinity gradients between river and sea waterand to desalinate water-using charge-discharge cycles of capacitors. Nanoporous electrodes increase the contact area with the electrolyte and hence, in principle, also the performance of the process. However, models to design and optimize devices should be used with caution when the size of the pores becomes comparable to that of ions and water molecules. Here, we address this issue by simulating realistic capacitors based on aqueous electrolytes and nanoporous carbide-derived carbon (CDC) electrodes, accounting for both their complex structure and their polarization by the electrolyte under applied voltage. We compute the capacitance for two salt concentrations and validate our simulations by comparison with cyclic voltammetry experiments. We discuss the predictions of Debye-Hückel and Poisson-Boltzmann theories, as well as modified Donnan models, and we show that the latter can be parametrized using the molecular simulation results at high concentration. This then allows us to extrapolate the capacitance and salt adsorption capacity at lower concentrations, which cannot be simulated, finding a reasonable agreement with the experimental capacitance. We analyze the solvation of ions and their confinement within the electrodes-microscopic properties that are much more difficult to obtain experimentally than the electrochemical response but very important to understand the mechanisms at play. We finally discuss the implications of our findings for CapMix and CDI, both from the modeling point of view and from the use of CDCs in these contexts.

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Water permeability of nanoporous graphene at realistic pressures for reverse osmosis desalination

Cited by 171 publications

References 16 publications

Nanoporous graphene as a reverse osmosis membrane: Recent insights from theory and simulation

Nanoporous graphene as a reverse osmosis membrane: Recent insights from theory and simulation

Water desalination using nanoporous single-layer graphene

Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models

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