Wettability improvement of ceramic membrane by intercalating nano-Al2O3 for oil and water separation

The objective of this study is to investigate the spontaneous wettability response of alumina nanocomposites deposited onto hollow fibre ceramic based membrane. Bare membrane was fabricated from kaolin powder using a phase inversion technique and sintering process. The nanocomposites were synthesized by varying alumina nanoparticles composition via a sol-gel method. A dip-coating approach was used to deposit perfluorooctanoate (PFO) with alumina nanoparticles and poly (diallyl dimethylammonium chloride) (PDDA) on the active layer of the hydrolysed bare membrane to improve on the inefficiency of the conventional oil/water separation materials and easy fouling of the bare ceramic membrane. Both the bare membrane and coated membrane were characterized using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle measurement. The performance of the membrane was tested for oil rejection and oil flux. The results suggest that higher sintering temperature improves the flexural strength of the bare membrane. The oil flux performance showed a decrease from 37.02 L/m2 h to 2.50 L/m2 h when the loadings of alumina nanocomposites (PDADMAC-Al2O3/PFO, PAP) coated onto the bare membrane was increased from 0.1 wt. to 0.6 wt., and in comparison, the oil rejection performance revealed an increase in the oil repellence from 80 to 98%. The oil contact angle was obtained at 125° after the chemical stability test in an acidic medium. The cogent mechanism of oleophobic and hydrophilic character of the coated membrane can be ascribed to the nano-scale hierarchical structure, as a result of alumina intercalated on the PFO. Alumina nanocomposite provides an excellent surface-coating material for ceramic-based hollow fibre membrane for oil-water separation to address the needs of wastewater industries.