Graphene membranes and water

Graphene separation membranes in six panels: nanoporous single-layer graphene for desalination, swollen and confined graphene-oxide laminates sieving ions, porous graphene sieving gases, protons crossing monolayer graphene, and an rGO-coated sponge separating oil from water.

1. Nanoporous graphene: Oxygen-plasma pores in monolayer graphene: salt rejection nearly 100 %, water flux up to 10⁶ g m⁻² s⁻¹ at 40 °C under a pressure difference (Surwade et al. 2015); in simulations, hydroxyl groups on the pore edge can roughly double the water flux (Cohen-Tanugi & Grossman 2012). 2. GO laminate, swollen: Immersed in water, GO laminates block all solutes with hydrated radii larger than 4.5 Å (Joshi et al. 2014); swollen laminates, d ≈ 13.5 Å, have a cut-off of ≈ 9 Å, larger than the hydrated ions of common salts (Abraham et al. 2017). 3. GO laminate, confined: Physically confined laminates, d from ≈ 9.8 to 6.4 Å, sieve below the size of hydrated ions; ion permeation falls exponentially while water transport changes by a factor below 2; 97 % rejection of NaCl (Abraham et al. 2017). 4. Gas sieving: After UV oxidative etching the membrane deflated about two orders of magnitude faster for H₂ and CO₂ than non-porous graphene, while Ar leaked as before (Koenig et al. 2012); unetched, it is impermeable to standard gases including helium (Bunch et al. 2008). 5. Protons: Monolayer graphene and hBN are highly permeable to thermal protons; no proton transport is detected through bilayer graphene, multilayer hBN or monolayer MoS₂ (Hu et al. 2014). 6. Oil–water separation: Melamine sponge coated with reduced graphene oxide is hydrophobic and oleophilic, stays afloat and takes up about 85 times its own weight of oil; regenerated with toluene it can be used again (Assis et al. 2026).

Starting materials: Single-layer graphene, graphene-oxide laminates, rGO-coated melamine sponge. Product: Membranes for water, ions, gases and protons; oil sorbents.

Surwade et al., “Water desalination using nanoporous single-layer graphene”, Nat. Nanotechnol. 2015 (doi:10.1038/nnano.2015.37); Joshi et al., “Precise and ultrafast molecular sieving through graphene oxide membranes”, Science 2014 (doi:10.1126/science.1245711); Abraham et al., “Tunable sieving of ions using graphene oxide membranes”, Nat. Nanotechnol. 2017 (doi:10.1038/nnano.2017.21); Koenig et al., “Selective molecular sieving through porous graphene”, Nat. Nanotechnol. 2012 (doi:10.1038/nnano.2012.162); Hu et al., “Proton transport through one-atom-thick crystals”, Nature 2014 (doi:10.1038/nature14015); Assis et al., “3D rGO and rGO/TiO₂-modified melamine sponges: sorbents for oil and emerging organic pollutant removal”, ACS Omega 2026 (doi:10.1021/acsomega.5c11602); Cohen-Tanugi & Grossman, “Water desalination across nanoporous graphene”, Nano Lett. 2012 (doi:10.1021/nl3012853); Bunch et al., “Impermeable atomic membranes from graphene sheets”, Nano Lett. 2008 (doi:10.1021/nl801457b); Nair et al., “Unimpeded permeation of water through helium-leak-tight graphene-based membranes”, Science 2012 (doi:10.1126/science.1211694).

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