Engineering of macroscale graphene oxide quantum dots skeleton membrane via electrostatic spraying method

In order to construct an efficient separation channel of graphene oxide quantum dots (GOQDs) membrane, a novel macroscale GOQDs skeleton membrane with the ethylenediamine (EDA) as the bridging agent was prepared for the first time by uniformly covering GOQDs nanosheets (∼2.78 nm) and EDA on the surface of the substrate membrane via electrostatic spraying method. The structure of the membrane was further optimized by post-crosslinking with trimesoyl chloride (TMC), and obtained the c-GOQDs skeleton membrane. The effects of spraying time and post-crosslinking on the structure and properties of as-prepared membranes were studied. The results showed that the obtained macroscale GOQDs skeleton membrane exhibited excellent separation effect for salt and dye. The introduction of EDA reconstructed the structure of the GOQDs skeleton separation layer, which made the separation layer structure loose and contributed to accelerating the water transmission speed. Thus, the permeation flux of GOQDs skeleton membrane (M-2, 155.6 L m−2 h−1, 3 bar) with similar dye rejection and lower bivalent salt rejection, was near 5 times than that of pure GOQDs membrane. Moreover, post-crosslinking could further improve the Congo Red rejection of c-GOQDs skeleton membrane (99.5%) with the higher salt/dye selectivity, which also showed high long-term operation stability and presented a potential application in dye desalination field.