Declining flux and narrowing nanochannels under wrinkles of compacted graphene oxide nanofiltration membranes

Graphene oxide (GO), prepared using Hummers method, is used to fabricate nanofiltration membranes by pressure-assisted self-assembly method. The reasons for the formation of wrinkles on the surface of GO membranes are analyzed in this paper. GO membranes have serious flux attenuation and obvious changes in surface morphology due to hydraulic pressure. At 1.0 MPa, the water flux of GO membranes decreases about 75%, while at 1.5 MPa, sodium sulfate rejection increases from 21.32% to 85.84%. GO membranes were compacted and wrinkles became narrower under the influence of hydraulic pressure. By comparing flux decline between support membranes and GO membranes and analyzing the structure of GO laminate, we concluded that flux decline is due to the changes in the support membrane and GO laminate synergistically. This study reveals a defect of GO membranes and provides a profound analysis of water permeation through GO membranes.