Graphene-induced tuning of the d-spacing of graphene oxide composite nanofiltration membranes for frictionless capillary action-induced enhancement of water permeability

While dispersing graphene in water is a formidable challenge, - stacking between graphene oxide (GO) and graphene is known to enable the dispersion of graphene in water. In this work, graphene-induced tuning of the d-spacing in GO composite membranes was performed by pressure-assisted self-assembly on a polysulphone inactive support. The physicochemical properties of the GO-graphene membranes were examined using numeric techniques, and the surface charges and hydrophilicities of the surfaces of GO-graphene membranes with different relative compositions of graphene were assessed. The incorporation of graphene into the GO layers was effective in inhibiting the swelling effect in the wet state; the different GO-graphene composite membranes also exhibited water permeability and salt rejection. The GO(1)graphene(0.8) composite membrane demonstrated a water flux of 36 LMH; salt rejection values of 88.3% (sodium chloride), 91.03% (magnesium chloride), 97.6% (magnesium sulphate) and 98.26% (sodium sulphate); and a minimal free volume. Hence, this sample is considered the optimal membrane. GO-incorporated graphene influences membrane performance by converting the Donnan effect to the molecular sieve mechanism. The GO-graphene composite membranes were compared via theoretical and experimental studies.