| The shortage of freshwater resources has become one of the most pressing global issues,posing an increasing threat to human society.Desalination of seawater or treatment of saline wastewater are considered effective ways to address this challenge,with membrane technology being one of the most promising approaches due to its efficiency,energy-saving features,and ease of integration.Graphene oxide（GO）has high specific surface area and allows for frictionless water transport in hydrophobic regions.By controlling the pores,charges,and wrinkles in the layers of GO,membranes can be produced that can selectively screen molecules and ions,making GO an excellent material for membrane separation in water treatment.In this study,modified composite membranes were prepared using a simple vacuum filtration technique through controllable reduction by vitamin C,and others by intercalation of nanosized SiO2 particles and cross-linking with polyacrylic acid（PAA）.The microstructure of the composite membrane was analyzed using SEM,TEM,XRD,AFM,etc.,and the water flux and salt rejection rate during the filtration of saltwater under atmospheric pressure were investigated.The saltwater separation mechanism was also proposed.The results are as follows:（1）The graphene oxide membrane（GOM）with folded and undulating surface and convex and undulating overlapping arrangement between lamellae was prepared by filtration using GO dispersion solution with a concentration of 2 mg·mL-1 under pressure of 0.1 MPa,with the interlayer spacing of 0.84 nm,the defect size on the lamellar range from 0.33 nm to 0.48 nm,and the Langmuir surface area of 47.99 m2·g-1,the static contact angle of 58.73°.The water flux and desalting rejection of the membrane for 1 g·L-1 NaCl solution were 16.1 L·m-2·h-1·MPa-1 and 21.6%,respectively.（2）The VC-rGOM composite membrane was prepared by reducing GO nanosheets using 0.04g vitamin C and 0.5 mL GO dispersion at a constant temperature of 45℃,with the interlayer spacing of 0.39～0.88 nm,the Langmuir surface area of 17.58 m2·g-1,the static contact angle of 76.8°,producing internal wrinkles with graphene oxide and reduced graphene oxide.The desalting rejection of the composite membrane for 1 g · L-1 NaCl solution at atmospheric pressure increased to 32.6%,while the water flux decreased to 12.47 L·m-2·h-1·MPa-1 coMPared to the GOM membrane.（3）The PAA@SiO2-GOM composite membrane was prepared by doping GO dispersion solution of 0.5 mL with the content of nanosized SiO2 particles of the ratio of one to five of GO and SiO2,by filtration using cross-linking reactions with PAA crosslinking reaction of 10 μL under pressure of 0.1 MPa,with the interlayer spacing of 1.71～6.84 nm,the static contact angle of 26.45°,the Langmuir surface area of 61.97 m2·g-1,producing tiny wavy fold structures on the surface and lattice fringe structures in the range of 0.33～0.35 nm inside.The desalting rejection for a 35 g·L-1 NaCl salt solution at atmospheric pressure was 27%,while the water flux was 386 L·m-2·h-1·MPa-1,approximately 1400 times that of the GOM membrane.（4）It is proposed that the desalting mechanism of GO and its composite membranes is the steric hindrance effect caused by the fold barrier structure on the membrane surface,the size effect caused by the micropore defects caused by modified doping,and combined with the Donnan charge effect. |
