Syntheses of four novel silicate-based nanomaterials from coal gangue for the capture of CO2

As one of the most important approaches to reduce CO 2 emission from various combustion processes, CO 2 adsorption capture is facing several many challenges, including high adsorbent cost, high energy cost, and low CO 2 selectivity. In this work, four novel silicate-based nanomaterials (SBNMs), including magnesium silicate (MgSiO 3 ), manganese silicate (MnSiO 3 ), copper silicate (CuSiO 3 ) and zirconium silicate (ZrSiO 4 ), were fabricated via hydrothermal method with SiO 3 2− extracted from coal gangue (CG) for the adsorption capture of CO 2 . Under the optimum conditions, the SiO 3 2− extraction ratio from the CG reached to 77.69%. The extracted SiO 3 2− was used to synthesize SBNMs with high surface area and high thermal stability, which were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and nitrogen adsorption/desorption isotherms technologies. These as-obtained SBNMs exhibited CO 2 adsorption capability of (7.82–17.93) cm 3 /g at 25 °C under 1 atm, respectively. The CO 2 adsorption data were successfully fitted with Freundlich model, and the adsorption processes were obvious chemically favored, spontaneous and exothermic according to thermodynamic parameters, including Q st , Δ G ads , Δ H ads and Δ S ads . Significantly, all SBNMs showed a excellent cycle performance and strong selectivity toward CO 2 over N 2 . The aim of this work is to provide a new method of utilization of coal gangue waste and a low-cost, and highly selective CO 2 adsorbents.