Preparation of metakaolin-based geopolymer membrane and its application in black liquor treatment

In recent years, inorganic membrane filtration technology has become the most promising treatment option for treating papermaking black liquor and recovering lignin from black liquor. However, the preparation of most inorganic membranes requires sintering or high-cost raw materials, which leads to high cost in the application of black liquor treatment and lignin recovery. For this reason, in this study, a no-sintering, low-cost metakaolin-based geopolymer membranes (MGM) was prepared at room temperature using steel mesh with good ductility and processability as the substrate. The effects of slag doping on the mechanical properties, microstructure and separation properties of MGM were investigated. The results concluded that when the mass ratio of slag to metakaolin is 1:10 (MGM-10), the membrane has the best comprehensive performance. The compressive strength and pure water flux of MGM-10 were 23.94 MPa and 286.62 kg m−2 h−1, respectively. In the application of black liquor treatment and lignin separation and recovery from black liquor, MGM-10 showed excellent separation performance by removing 96% of TSS, 91.75% of COD and 98.97% of BL from black liquor after primary filtration. Compared with ceramic membranes prepared by sintering, MGM has cheaper raw materials and lower energy consumption, which is more promising for industrial scale applications.