Preparation and characterization of a self-supporting inorganic membrane based on metakaolin-based geopolymers

This paper is focused on a new self-supporting inorganic membrane prepared by a one-time cast molding process with geopolymer paste. This new preparation method has the advantages of easy fabrication, free sintering and low cost compared with the conventional inorganic membrane preparation methods. This work explores the influence of the H2O/Na2O molar ratio on the strength and porous structure of the inorganic membrane. A linear relationship between the permeated water flux and the membrane thickness or operating pressure was observed after a filtration test. By optimizing processing parameters, this study obtained an inorganic membrane (with the H2O/Na2O molar ratio of 18) between the ultrafiltration membrane and the microfiltration membrane with a high compressive strength of 20 MPa, a pore size distribution of 20 to 100 nm, a rejection rate of 100% for nano-Al2O3 particles and a permeated water flux of 185 kg/m2h when the operating pressure was 0.3 MPa and the membrane thickness was 5.0 mm. This membrane will be a good choice for the field of water treatment with membranes.