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

Abstract As one of the most important approaches to reduce CO2 emission from various combustion processes, CO2 adsorption capture is facing several many challenges, including high adsorbent cost, high energy cost, and low CO2 selectivity. In this work, four novel silicate-based nanomaterials (SBNMs), including magnesium silicate (MgSiO3), manganese silicate (MnSiO3), copper silicate (CuSiO3) and zirconium silicate (ZrSiO4), were fabricated via hydrothermal method with SiO32− extracted from coal gangue (CG) for the adsorption capture of CO2. Under the optimum conditions, the SiO32− extraction ratio from the CG reached to 77.69%. The extracted SiO32− 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 CO2 adsorption capability of (7.82–17.93) cm3/g at 25 °C under 1 atm, respectively. The CO2 adsorption data were successfully fitted with Freundlich model, and the adsorption processes were obvious chemically favored, spontaneous and exothermic according to thermodynamic parameters, including Qst, ΔGads, ΔHads and ΔSads. Significantly, all SBNMs showed a excellent cycle performance and strong selectivity toward CO2 over N2. The aim of this work is to provide a new method of utilization of coal gangue waste and a low-cost, and highly selective CO2 adsorbents.