Synthesis of mesoporous sodalite from coal-fired slag for CO2 capture

Sodalite (SOD) is a type of zeolite molecular sieve, which owns the functions of sieving molecules, including adsorption, ion exchange and catalysis. In this work, coal-fired slag (CFS) is de-hybridized to increase the content of SiO2 in the CFS to 76.5 %, and then the de-hybridized CFS is used as raw material to prepare the SOD by alkali fusion hydrothermal synthesis. The optimum preparation conditions are confirmed at the slag to alkali ratio of 1: 1.0, solid to liquid ratio of 1:3.5, hydrothermal temperature of 180 °C, and hydrothermal time of 12 h, which can produce high crystallinity CFS-based SOD with uniform morphology. After that, the adsorption capacity of CO2 on the SOD was determined at 1.87 cm3/g, which was 38 times higher than the adsorption capacity for N2, so that the SOD presented high selective adsorption capability for CO2/N2 mixture. This study provides a strategy for the resource utilization of solid waste and the preparation of low-cost high-performance adsorbents.