A low-cost alumina-mullite composite hollow fiber ceramic membrane fabricated via phase-inversion and sintering method

With abundant bauxite mineral as starting material, a low-cost alumina-mullite composite hollow fiber ceramic membrane (HFCM) was fabricated via phase-inversion method followed by high temperature sintering. Process parameters, including bore fluid flow rate and air-gap distance, which affect structure and properties of the HFCM were systematically explored. A low bore fluid flow rate would lead to the deformation of inner walls of the HFCM as a result of insufficient solidification, while a large air-gap distance would induce the distortion of finger-like voids. Effects of sintering on the microstructure, pore size distribution, nitrogen gas flux and mechanical properties were investigated in details. Acid-base titration was first proposed to quantitatively determine concentration of surface active sites of membrane surface after sintering. An increase in sintering temperature leads to significantly enhancing strength but almost linearly reduces concentration of active surface hydroxyl sites. Compared with its alumina counterpart, this low-cost composite membrane can be sintered at lower sintering temperature, and exhibits higher mechanical strength and active surface hydroxyl site concentration.