CuO and ZnO doped SiO2 ceramic membranes prepared via sol-gel method for enhanced CO2/N2 separation

To reduce carbon emissions in flue gas and enhance CO 2 permeation and separation performance, this study innovatively used Cu(NO 3 ) 2 ·3H 2 O and Zn(NO 3 ) 2 ·6H 2 O as precursors for CuO and ZnO. By employing the sol-gel method combined with high-temperature sintering technology, CuO/SiO 2 , ZnO/SiO 2 , and CuO-ZnO/SiO 2 membranes were successfully prepared.The fitting result of the Freundlich model (R 2 =0.996) confirms that the CuO/SiO 2 membrane material has heterogeneous physical adsorption sites, which are beneficial for CO 2 capture. At 0.35 MPa, the apparent permeation activation energy (E a ) of CO 2 for the CuO/SiO 2 membrane is the lowest, approximately 0.65 kJ·mol -1 . In terms of CO 2 permeance and CO 2 /N 2 permselectivity, the performance ranking of the membranes is as follows: CuO/SiO 2 membrane>CuO-ZnO/SiO 2 membrane>ZnO/SiO 2 membrane. Under the conditions of 0.35 MPa and 200 °C, the CO 2 permeance and CO 2 /N 2 permselectivity of the CuO/SiO 2 membrane is approximately 2.21×10 -7 mol·m -2 ·Pa -1 ·s -1 and 12.7, respectively, which is increased about 10 times and 6 times than that of the SiO 2 membrane. Additionally, the CuO/SiO 2 membrane maintains good CO 2 separation efficiency during steam treatment and subsequent regeneration processes. These findings provide new insights for research on improving the CO 2 /N 2 separation performance of SiO 2 ceramic composite membranes.