Facile fabrication of 3D ferrous ion crosslinked graphene oxide hydrogel membranes for excellent water purification

3D graphene-based macrostructures have been recognized as promising candidates for adsorption and separation of water pollutants due to their well-defined porous structures and high surface areas. In this work, 3D graphene oxide hydrogel membranes (GOHMs) are fabricated by gelation of GO with ferrous ions via vacuum filtration. The ferrous ions serve as cross-linkers to increase the bonding strength between GO nanosheets and to induce microstructure transformation of GO via cation–π interactions to form a 3D lamellar porous structure. Compared with the pure GO membrane, GOHMs not only display high stability in water but also show considerably improved water permeability (111.5 L m−2 h−1 bar−1) and retention performances (>99%) for methylene blue (MB), because the hydrogel structure impressively enhances the connectivity of nanopores as well as the adsorption capacity. In addition, the nanostructures of GOHMs can be controlled by adjusting the amounts of GO or ferrous ions. The water permeation and MB retention reveal the structural changes of different GOHMs, which are consistent with the observations from scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, GOHMs exhibit high permeation and separation performances in a wide pH range, and could effectively remove diverse organic contaminants by a facile filtration process via different separation mechanisms. Therefore, the GOHMs demonstrate a promising technique for practical wastewater purification.