Synthesis of mesoporous magnesium silicate from coal gangue for efficient CO2 adsorption at room temperature

Abstract

Solid adsorbents are widely investigated for CO2 capture, but some of them show low cycle stability and high synthesis cost. In this work, coal gangue (CG) as the raw material reacts with MgCl2 by the stirring way to synthesize mesoporous magnesium silicate (MMS) for efficient CO2 adsorption at room temperature. Meanwhile, the optimal synthesis condition of MMS was finally confirmed on the basis of single factor and response surface strategies: pH = 10.00, 1: 1 of Mg/Si molar ratio, 80 °C of the reaction temperature, and 2 h of reaction time. Under this condition, the as-synthesized MMS presented 1.02 mmol/g of CO2 adsorption amount at 25 °C, which adsorbed 33 times more CO2 than N2. The MMS owns a 373.00 m2/g of specific surface area and mesoporous structure. The adsorption thermodynamics and cycle performance of CO2 were discussed. After 10 cycles, the adsorption amount of MMS still maintained to 86 % of the initial value. The adsorption is exothermic and spontaneous physical process. The MMS was shown to have high CO2 adsorption capacity and selectivity. This work presents an application potential for the efficient utilization of CG and the development of CO2 adsorbents.