## 1 Introduction  
Membrane filtration processes are used extensively in water treatment and in food processing and pharmaceutical industries because they provide advantages such as being energy efficient and easy to operate at room temperature [1]. Membrane properties play an important role in the filtration process, and problems such as membrane fouling and low water flux have limited the application of this technology [2]. Several characteristic membrane parameters (such as hydrophilicity, surface roughness, pore size, and surface charge) have an influence on membrane antifouling properties [3]. Many efforts have been made to improve the hydrophilicity and antifouling properties of membranes, including the use of physical blending, plasma treatment, polymer grafting, and chemical reactions, and it is known that the most effective modification methods involve blending membranes with inorganic nanoparticles, such as Al\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), SiO\({}_{2}\), and ZrO\({}_{2}\)[4; 5; 6; 7].  
Recently, carbon nanomaterials (such as carbon nanotubes (CNTs)) and graphene-based nanomaterials have been used to prepare membranes and improve their properties, and high permeability, excellent ion rejection, and antifouling effects have been determined [8; 9; 10]. Graphene is a single atomic plane of graphite that exhibits unique electronic, thermal, and mechanical properties [11]. Furthermore, exfoliated graphene oxide (GO) contains various hydrophilic functional groups, such as hydroxyl, epoxide, and carboxyl groups, and it could thus be used to modify membrane surfaces and alter characteristics from hydrophobic to hydrophilic [12]. Reduced graphene oxide (rGO) has fewer functional groups than GO, but its \(sp^{2}\) structures and physical properties can still be recovered. rGO is a material closer to the graphene properties obtained through reduction; it is purer than GO, and its application has been continuously researched [13; 14; 15; 16]. Therefore, its ability to enhance the mechanical strength of water treatment membranes requires investigation, even though it may be difficult to expect the hydrophilic effects of rGO.  
Polysulfone (PSf) based membranes are predominantly used in membrane filtration processes because they provide excellent heat resistance, chemical compatibility, and mechanical resistance over a wide pH range [9; 17]. However, polyvinylidene fluoride (PVDF) has also received tremendous attention with respect to its industrial application and, particularly, for its use in wastewater treatment, as it has a high mechanical strength, is thermally stable, is chemically resistant, and is of high purity [4]. However, the inherent hydrophobic characteristic of polymers (such as PSf and PVDF) often result in severe membrane fouling and a decline in permeability, and this has been a barrier for their further development and application in treating water. There have been several research papers reporting the membrane mixed with GO, but no papers have compared GO and rGO and at the same time compare PSf and PVDF membranes. In this study, therefore, PSf and PVDF membranes blended with GO and rGO were fabricated to comparatively investigate any increases in surface hydrophilicity and antifouling properties.