Fabrication of superhydrophobic/superoleophilic functionalized reduced graphene oxide/polydopamine/PFDT membrane for efficient oil/water separation

Abstract

A superhydrophobic/superoleophilic (SS) reduced graphene oxide-polydopamine functionalized with 1H,1H,2H,2H-perfluorodecanethiol (rGO-PDA-PFDT) membrane was successfully fabricated by a facile and simple two-step method. The surface morphology and chemical composition were thoroughly investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, UV–vis spectrophotometry, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS). The wetting properties were assessed using water contact angle (WCA) measurements. The as-prepared rGO-PDA-PFDT membrane displayed a WCA of about 156°, and the water droplet can leave the surface without hysteresis, indicating a stable Cassie-Baxter state. Using the Cassie-Baxter model, we found that approximately 7% serves as the contact area of the water droplet and the solid surface, and the remaining 93% represents the contact area of the water droplet and air. Organic solvents such as chloroform, hexane, toluene, acetone, and 1-octane wet completely the surface, indicating superoleophilicity. The superhydrophobic/superoleophilic (SS) membrane was highly stable even in harsh environments such as acid and alkaline media. The rGO-PDA-PFDT was filtered on Whatman filter paper to obtain a membrane and was subsequently applied for oil/water separation. The rGO-PDA-PFDT membrane was able to separate chloroform from water owing to its superhydrophobicity and superoleophilicity. Additionally, the membrane can be reused for 10 repetitive separation cycles without any apparent loss of its performance. These properties are expected to promote the application of the rGO-PDA-PFDT membrane in various environmental processes.