A facile approach for the development of fine-tuned self-standing graphene oxide membranes and their gas and vapor separation performance

It was demonstrated that the GO porosity strongly depends on the filtration rate: a fast filtration of the GO suspension led to a haphazard arrangement of GO stacks and, as consequence, to a higher porosity; on the other hand, a very slow filtration resulted in more ordered structures, with the individual GO layers arranged one on top of the other, the voids corresponding to discontinuities in the stacking of the GO layers along the basal plane. The slow filtration derived membranes were almost impermeable to m-xylene vapor and exhibited a good separation performance for several gas pairs (H2/N2, H2/CO, H2/CH4, H2/C2H6, H2/C4H10 and H2/SF6) exceeding nearly twice those corresponding to Knudsen type of diffusion. In addition, the more hydrophobic membranes (prepared using GO with a lower concentration of oxygen surface groups) exhibited very high H2O vapor permeances that make them excellent candidates for application in membrane distillation processes.