Scalable fabrication of deoxygenated graphene oxide nanofiltration membrane by continuous slot-die coating

Abstract

Graphene oxide (GO) has been widely used for the fabrication of nanofiltration membranes because precise molecular sieving can be achieved through the narrow interlayer spacing between stacked GO sheets. Herein, the scalable and continuous fabrication of a GO membrane is demonstrated by using a slot-die coater at a coating speed of 6 mm s−1. The thickness of the GO membrane can be controlled in 100-nm scale depending on the concentration of the GO solution and substrate morphology. Moreover, the coating layer and d-spacing (6.5–7.5 Å) of the GO membrane is preserved, even in aqueous solution, as GO is partially reduced by NaOH treatment (so-called deoxygenated GO, dGO). A membrane performance test reveals that the dGO membrane is effective for filtering sub-nanometer-size dye molecules with a rejection rate of up to 99% (brilliant blue G) and a pure water permeance of 30 LMH bar−1. The dGO membrane operates stably under cross-flow and high pressure up to 12 bar. Scale-up of the GO membrane fabrication using the slot-die coating technique is feasible because the coating process is continuous.