An Optimum Routine for Surface Modification of Ceramic Supports to Facilitate Deposition of Defect-Free Overlaying Micro and Meso (Nano) Porous Membrane

In this work, a simple and effective way to modify the support surface is developed and a nanostructure ceramic support to facilitate deposition of a defect-free overlying micro and meso (nano) porous membrane is obtained. To achieve high performance nanocomposite membranes, average pore size of outer surface of support was reduced by dip-coating in submicron and nano ?-alumina slurries. In this respect, the effects of several parameters such as: solid content, dipping time, vacuum pressure, heating rate and number of coated layers on microstructure of the fabricated layers were investigated. The obtained results showed that the optimum routine for this technique was twice coating of 5wt% submicron slurry without applying vacuum followed by vacuum dip-coating of 5wt% submicron and 1wt% nano alumina slurry. Pore size of the unmodified membrane support was calculated using permeance data and the obtained result was 540 nm. After twice modification with submicron alumina slurry without vacuum, average pore size of surface decreases significantly. More surface modification by vacuum dip-coating of alumina submicron and nano particles slurries results in decreasing of average pore size of intermediate layers to nanometric scale ( < 100 nm), respectively. The obtained results are confirmed by mercury porosimetry measurements.