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

• SiO 3 2− from coal gangue to prepare four nano-materials for CO 2 adsorption. • A high SiO 3 2− leaching rate of 77.69% from coal gangue. • Optimal preparing conditions for nano-materials by surface response analysis. • Four nanomaterials with high capability for recycle CO 2 capture with high selectivity. 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) cm3/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 Qst, 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. [ABSTRACT FROM AUTHOR]