Enhanced desalination performance of carboxyl functionalized graphene oxide nanofiltration membranes

The desalting performance of graphene oxide (GO) membranes was further optimized using one-step carboxylation via nucleophilic substitution reactions between epoxy groups of graphene oxide (GO) and amino groups of glycine. GO and GO-COOH membranes with highly ordered structure were prepared by pressure-assisted self-assembly technique. The performance of GO and GO-COOH membranes was investigated and compared. The results showed that GO-COOH membranes exhibited not only higher permeability but also better salt rejections compared with pristine GO membranes. The surface physicochemical properties of GO-COOH membrane including negativity and hydrophilicity were improved as well. The transport mechanism revealed that the improvement of desalting properties was attributed to enhanced electrostatic repulsion by inducing effective negative charge. The higher permeability of GO-COOH membranes resulted from increased water nanochannels and improved surface hydrophilicity. Overall, GO-COOH membranes show great potential in the separation field due to prominent permeation performance and desirable separation property. •GO-COOH nanosheets were successfully fabricated via nucleophilic substitution.•Carboxylation improved the surface physicochemical properties of membranes.•GO-COOH membranes exhibited higher water flux and salt rejections than GO mambranes.