Synthesis of zeolite molecular sieve 13X from coal-fired slag for efficient room temperature CO2 adsorption

Coal-fired slag (CFS) was used to successfully synthesize zeolite molecular sieve (ZMS) 13X by the alkali fusion hydrothermal method for efficient room-temperature CO2 adsorption. The optimum synthesis conditions of ZMS 13X were confirmed using the single-factor and Box-Behnken methods. With a specific surface area of 585.67 m2·g−1, the resultant ZMS 13X is a mesoporous material with good CO2 adsorption selectivity and cyclic performance. At 25 °C and 1 bar, the initial CO2 adsorption amount presented 3.69 mmol·g−1 and still maintained 3.37 mmol·g−1 of CO2 adsorption amount after 10 cycles. The Langmuir isotherm model can well describe the CO2 adsorption process of ZMS 13X as an entropy-decreasing physical adsorption process with the intermolecular interaction of van der Waals forces. Therefore, this work proposes a new strategy for the low-cost synthesis of ZMS 13 from the CFS solid waste for efficient room-temperature CO2 capture.