Melded ceramic membranes: A novel fabrication method for ultrathin alumina membranes of high performance

Abstract

Conventional ceramic membranes are usually fabricated on porous ceramic substrates, using a repetitive coating-sintering process to form a multilayered structure. This results in lengthy fabrication periods and high fabrication costs. In this work, we developed a novel fabrication process, melding, by combining vacuum infiltration and pore tuning techniques to directly construct the ceramic membrane layer within the porous ceramic substrate. By careful selection of powder sizes, the detrimental penetration effect can be modified into a benefit, forming an ultrathin membrane layer with thickness less than 1.45 µm after sintering at 1200 • C. Compared favorably with dip-coated ceramic membranes, the melded ceramic membrane had much smaller nominal pore sizes (0.19 vs 0.31 µm), but much higher water permeance (>60%). The melded ceramic membrane also had the highest rejection (98.5%) toward 125 nm polystyrene latex suspensions (2 ppm), highest sustained oil removal efficiency (>90%) under oilin-water emulsion (200 ppm) filtration, and the least irreversible fouling (<8.6%). The melding process also significantly reduced the raw powders required, leading to an 86% reduction in material costs, as compared to the multilayered ceramic membranes.