A mussel-induced method to fabricate reduced graphene oxide/halloysite nanotubes membranes for multifunctional applications in water purification and oil/water separation

In this work, a reduced graphene oxide/halloysite nanotubes (RGO/HNTs) membrane was synthesized via polydopamine (PDA) modification and assembly on the surface of commercial cellulose acetate (CA) membrane constituting a PDA/RGO/HNT-CA membrane. The PDA/RGO/HNTs was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and transmission electron microscopy (TEM). In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to detect the surface morphology structure and roughness of composite membranes, respectively. A hydrophilicity experiment demonstrated that the flux of PDA/RGO/HNT membrane was dramatically improved with an increasing HNT ratio and the retention rates of Methylene Blue (MB), Congo Red (CR), Cu2+, and Cr3+ were 99.72%, 99.09%, 99.74% and 99.01%, respectively. The separation rate of oil/water emulsion was about 99.85% for 0.15 g PDA/RGO/HNTs membrane. More importantly, the recycle and anti-fouling tests indicated that the HNTs-modified membrane exhibited the superior anti-fouling capacity after three cycles. Herein, it can be expected that this type of membrane has great potential as a promising candidate in practical water purification.