Preparation of nano-sized Mg-doped copper silicate materials using coal gangue as the raw material and its characterization for CO 2 adsorption

This work presents a simple method for the preparation of the Mg-doped nanocomposite copper silicates (Mgx-Cu1−x-SiO3) (x=0.25, 0.5, 0.75 and 0.9) using coal gangue waste as the silicon source for CO2 capture at low temperature. The as-prepared Mgx-Cu1−x-SiO3 was systemically characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller surface area analysis (BET). The results suggest that all Mgx-Cu1−x-SiO3 possess large surface areas, micropores and mesoporous structures composed of the agglomerates of small nanoparticles. They exhibit high CO2 adsorption capacity at 298.15 K under 1 bar, and that of Mg0.9-Cu0.1-SiO3 was the highest with the value of 16.73 cm3/g. The Freundlich isotherm model fits the CO2 adsorption isotherm well. Thermodynamic analysis indicates that the CO2 adsorption on Mg0.9-Cu0.1-SiO3 is exothermic (ΔH°<0), chaotic (ΔS°<0), and spontaneous (ΔG°<0). This work highlights the low-temperature adsorption behavior of silicate materials on CO2, which can provide some research basis for the utilization of silica in coal gangue.