Multifunctional iron oxide supported alumina/yttria stabilized zirconia hollow fiber adsorptive membrane for water treatment

Abstract

Ceramic membrane offers high thermal, mechanical and chemical resistance. It also has been regarded as an alternative membrane for water separation application. In this study, a composite aluminium oxide/yttria-stabilized zirconia (Al2O3/YSZ) hollow fiber membrane was fabricated via the combined dry-wet phase inversion spinning method and sintering process. The findings had observed an asymmetrical membrane structure consisting of the finger-like voids and sponge-like voids. The addition of YSZ had improved the mechanical strength of the membrane produced despite the porous structure and thin wall thickness. The findings had concluded that the Al2O3/YSZ hollow fiber membrane prepared using the composite of 0.3 μm YSZ particle and sintered at 1350 oC (HF0.3-1350 membrane) was selected as the substrate for iron oxide (Fe2O3) deposition. This is due to the HF0.3-1350 measured to be having the highest water flux. Next, the deposition of Fe2O3 on the Al2O3/YSZ hollow fiber membrane was carried out using the hydrothermal process. The hydrothermal process is a facile process and the Fe2O3 particles can be simultaneously synthesized and deposited. For the application of an adsorptive membrane for lead (Pb) removal, the Fe2O3 particles were deposited onto the porous structure of the membrane. The performance showed high Pb (II) removal at pH 7, with fast removal within the first 10 min of the filtration process and had reached the equilibrium at 60 min. Moreover, the kinetic isotherm of pristine, F005-24 and F02-24 membrane followed the pseudo-second-order kinetics model. This study proved that the Fe2O3 deposition played an indispensable role in improving the adsorption capability of the pristine membrane towards Pb (II) ions. For the application of oil emulsion separation, the Fe2O3 particles were deposited on the outer surface of the Al2O3/YSZ hollow fiber membrane. Then, depositing at the hydrothermal concentration above 0.2 M, Fe2O3 layer was formed. The findings have shown that the Fe2O3 layer gave increment to the water flux and oil rejection of the membrane. Then, the property of Fe2O3 itself as a photocatalyst gave other functionalities of the membrane for the photocatalytic process. Therein, the stimulated photo-induced separation system was operated for the Fe2O3 supported Al2O3/YSZ hollow fiber membrane to highlight the self-cleaning mechanism of the membrane. The finding recorded was that the flux and oil rejection increases with the light assisted throughout the separation process. Lastly, the polymer coating of UV curable resin (UVR) on the outer membrane surface had preserved the Fe2O3 layer from the delamination. The UVR layer formed had changed the surface properties of the membrane from hydrophilic to hydrophobic. The existence of the UVR layer had highlighted the potential of the hydrophobic UVR-coated ceramic hollow fiber membrane for water separation using the sweeping liquid filtration system. The F02-UVR membrane was able to remove 94% of humic acid with a flux of 46.53 kg/m2.h. The outcome of this study was the multifunctional Fe2O3 supported Al2O3/YSZ hollow fiber adsorptive membrane can be used for the treatment of different water pollutant.