Nanowires versus nanosheets – Effects of NiCo2O4 nanostructures on ceramic membrane permeability and fouling potential

Abstract

Two types of alumina membranes respectively modified by nickel–cobalt oxide (NiCo2O4) nanowires (NW) and nanosheets (NS) on surfaces were prepared and investigated for their filtration performance. The NW and NS surface layers were found to be significantly more hydrophilic and smoother than the pristine ceramic membrane. However, water fluxes of the NW- and NS-surface-modified membranes were significantly lower than that of the pristine membrane, due to the pore blocking by the NW/NS layers. Nevertheless, water flux of NS-modified alumina membrane was 50% lower than that of the NW-modified with a membrane resistance of 40% higher, because the NS structure was collapsed under the dead-end filtration pressure and had further blocked the pores evidenced by studies using scanning electron microscopy. Both membranes exhibited similar organic fouling potentials, determined by the resistance to the formation of alginate or serum albumin layer on the membrane surfaces. Resistances caused by carbohydrate fouling were found to be nearly twice that caused by protein fouling, due to the reduction in hydrophobic-hydrophobic surface interactions. The NW-modified alumina membrane showed the lowest biofilm formation determined by the number of live cells on the membrane surface, since the fibrous surfaces had prevented cells from attachment. The results in the present study demonstrated that the NW modification was more suitable for water filtration due to better structure stability, lower fouling potential and membrane resistance.