Enhanced permeability and biofouling mitigation of forward osmosis membranes via grafting graphene quantum dots

In this paper, graphene oxide quantum dots with amino groups (NH2-GOQDs) were tailored to the surface of a thin-film composite (TFC) membrane surface for optimizing forward osmosis (FO) membrane performance using the amide coupling reaction. The results jointly demonstrated hydrophilicity and surface roughness of the membrane enhanced after grafting NH2-GOQDs, leading to the optimized affinity and the contact area between the membrane and water molecules. Therefore, grafting of the membrane with a concentration of 100 ppm (TFC-100) exhibited excellent permeability performance (58.32 L.m(-2).h(-1)) compared with TFC membrane (16.94 L.m(-2).h(-1)). In the evaluation of static antibacterial properties of membranes, TFC-100 membrane destroyed the cell morphology of Escherichia coli (E. coli) and reduced the degree of bacterial adsorption. In the dynamic biofouling experiment, TFC-100 membrane showed a lower flux decline than TFC membrane. After the physical cleaning, the flux of TFC-100 membrane could recover to 96% of the initial flux, which was notably better than that of TFC membrane (63%). Additionally, the extended Derjaguin-Landau-Verwey-Overbeek analysis of the affinity between pollutants and membrane surface verified that NH2-GOQDs alleviates E. coli contamination of membrane. This work highlights the potential applications of NH2-GOQDs for optimizing permeability and biofouling mitigation of FO membranes.