Graphene oxide (GO) composite membranes revealed exceptional promise for advanced water/wastewater treatment applications. In this study, a novel GO-based membrane system was developed through strategic material engineering and surface functionalization. GO nanosheets were precisely deposited onto modified α-alumina ceramic supports via filtration and characterized with comprehensive characterization using TEM, FTIR, XRD, Raman, WCA, AFM, and FESEM analyses. The bare GO membrane exhibited outstanding water permeability of 3.14 ± 0.17 LMH.bar⁻1; however, it showed relatively low rejection rates for Ca2⁺ and Cr (VI), i.e., 68.0 and 80.5%, respectively. Some holey graphene oxide (HGO) nanosheets were also prepared through controlled chemical etching (3 and 5 h, i.e., HGO-3 and HGO-5), and 2.5- and 3.14-fold increments were observed for HGO-3 and HGO-5 composite membranes, respectively, as compared to the bare GO membrane with lower rejection rates. To compensate for the loss in the rejection rates, ethylenediamine (EDA) crosslinking was performed to stabilize the membrane rejection rates. The HGO-3-EDA membrane kept its superior permeability at 6.29 ± 0.57 LMH.bar−1 and significantly recovered its Ca2⁺ and Cr (VI) rejection rates at 66.1 and 76.5%, respectively. Furthermore, advancement came through PEI surface functionalization, which dramatically enhanced Ca2⁺ (80.9%) and Cr (VI, 92.9%) rejections while maintaining high permeability of 5.90 ± 0.24 LMH.bar−1, which is still 1.9-fold higher than that of the bare GO membrane. This work establishes a new paradigm in membrane design by successfully overcoming the traditional permeability-selectivity trade-off through innovative material engineering approaches.
