For ideal membrane fitting for diff

For ideal membrane fitting for different applications, it is necessary to design it with gradual pore sizes from the outer side to the inner side.To make gradual decrease in the open pore sizes and to improve the antibacterial activities of the membrane surface, nanosized materials having higher surface area and antibacterial activity should be coated
on the membrane support. In the present study, as indicated before, the final fabricated ceramic membrane composed mainly of alumina sub-
strate coated with synthesized anatase nano wire. This means that the cross-section of membrane consists of three layers; namely, the first layer is the ceramic support (alumina), the second layer is the inter-mediate or interface layer and the top separation layer which is the functional layer containing TiO 2 nano wires. Therefore, the interface offinal membrane consists of Al 2 O 3 from support and TiO 2 derived from the top layer due to the diffusion through porous materials. On the
other hand, the fabricated sintered porous alumina support has about 58% open porosity and 18 MPa cold crashing strength which are sui-table properties for such kind of membranes. In this work, scanning electron microscope was used to investigate the microstructure, pore shape and pore size of the fabricated membrane. Fig. 8 shows SEM
micrographs of fabricated membrane after heat treatment at 550 °C. Different microstructure features are exhibited in these micrographs.
The microstructure of membrane cross section is show in Fig. 8a. In this microstructure, only two layers are clearly appeared. The top layer is
similar to aligned oriented TiO 2 nano wires while the bottom layer is the porous alumina substrate. The bottom layer has a homogenous
microstructure with relatively different grain sizes and pore size ran- ging from 5.84 to 13.8 µm as calculated from the microstructure image(Fig. 8b). The microstructure of the interface layer is more homogenous and exhibit comparable grain size and pore sizes (Fig. 8c). Their sizes are ranging between 1.42–5.29 µm. On the other side, the micro-structure of top layer exhibit randomly oriented TiO 2 nano wires homogenously distributed on the substrate surface. Their pore sizes are in the nano range. This means that the membrane has a gradual change in pore size as well as layer thickness from one layer to other for
achieving nanofiltration process.