Holey Graphene Oxide Membranes for Water Desalination
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Holey reduced graphene oxide (r-HGO) was investigated for next-generation nanofiltration membranes for water desalination. The GO nanosheets were first etched with hydrogen peroxide to create holes to enhance the water permeance. The holey GO (HGO) was then deposited on ultrafiltration membranes and reduced using hydroiodic acid (HI) aqueous solutions to improve the selectivity of the r-HGO membranes. The r-HGO was characterized using Fourier transform infrared spectrometer (FTIR), Raman spectroscopy, atomic force microscopy (AFM) and goniometer. The permeation properties of the r-HGO composite membranes are tunable via changing the preparation conditions, such as etching time, reduction degree and loading content. The highest pure water permeance can reach 30 Lm-2∙h-1∙bar-1 (LMH/bar) in 10 nm r-HGO-4-1.5 (where GO was etched for 4 h and reduced using a volume ratio of 1.5 for HI:H2O) while the rejection of Na2SO4 and NaCl is 68% and 30%, respectively. The highest rejection rate of Na2SO4 can achieve 99.1% with the water permeance around 0.63 LMH/bar for r-HGO-4-4. Thus the HGO composite membrane can be considered to be a promising candidate among next-generation nanofiltration membranes.