GO-Based Membrane As Barrier Against Toxic Vapors/Gases

Traditional protective garments loaded with activated carbons to remove toxic gases are bulky. Novel graphene oxide (GO) flake-based composite lamellar membrane was developed for a garment for protection against chemical warfare agent (CWA) simulants: dimethyl methyl phosphonate (DMMP) (a sarin-simulant); 2-chloroethyl ethyl sulfide (CEES) (a simulant for sulfur mustard); yet it has a high moisture transmission rate. GO flakes (300-800 nm, 0.7-1.2 nm thick) dispersed in water were formed into a membrane by vacuum filtration on porous polyethersulfone (PES) or poly (ether-ether-ketone) (PEEK) support membrane for noncovalent π-π interactions with GO flakes. After physical compression, Upright Cup tests indicated: it can block toluene for 3-4 days and DMMP for 5 days while exhibiting excellent water vapor permeation. Further, they have low permeances for small molecule gases/vapors. The GO flakes underwent crosslinking later with ethylenediamine (EDA) during vacuum filtration followed by physical compression and heating. With a further spray-coating of polyurethane (PU), these membranes could be bent without losing barrier properties vis-à-vis DMMP for 5 days; a membrane not subjected to bending blocked DMMP for 15 days. For the PEEK-EDA-GO-PU compressed membranes after bending, the separation factors of H₂O over others for low gas flow rates in the dynamic moisture permeation cell (DMPC) were: α_H2O-He, 42.3; α_H2O-N2, 110; α_H2O-ethane, 1800. At higher gas flow rates in the DMPC, moisture transport rate goes up considerably due to reduced boundary layer resistances and exceeds the breathable fabric threshold water vapor flux, 2000 g/m²-day. The membrane displayed considerable resistance to permeation by CEES as well. This behavior has been compared with that of a nanopacked bed of membrane supported nanocrystals of UiO-66-NH₂ MOF. The PES-EDA-GO-PU compressed membrane shows good mechanical property under tensile strength tests.