Preparation and characterization of a novel porous silicate material from coal gangue

• An innovative approach was developed to prepare the porous silicate material from coal gangue.
• The preparation method exhibited features of simple process and easily-obtained raw materials.
• The optimum thermal and chemical activation conditions on SiO32− leaching were confirmed.
• The optimum preparation conditions on the porous silicate material were confirmed.
• The porous silicate material showed strong adsorption capability towards CO2.

A novel porous silicate material (PSM) derived from coal gangue was successfully prepared and characterized by N2 adsorption–desorption isotherms, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction measurements. The preparation procedure involved two steps: (1) SiO32− leaching from coal gangue by both activation and chemical approaches, and (2) preparation of the PSM by reaction of the leachate with Ca(OH)2. It was found that the maximum SiO32− leaching yield was achieved at calcination temperature of 1000 °C, reaction temperature of 106 °C for 2 h, NaOH concentration of 25%, and the ratio of coal gangue to alkali of 0.5:1. The PSM was then easily prepared from the SiO32− leaching at 98 °C for 2 h with a Ca/Si ratio of 1.2:1 and the pH value of 12.70. The spectroscopic results showed that the PSM was mainly composed C, Ca, O, Si and Na, in the form of Ca2+, Na+, SiO32−, and CO32− ions. Some adsorbed water and/or surface water was observed. The adsorption behavior revealed that the CO2 adsorbed amount on PSM was 36.69 mg g−1 at 293.15 k and ambient pressure with a pure CO2 flow rate of 120 mL min−1 during 90 min.

SEM image of the PSM and TEM images of the PSM.Figure optionsDownload as PowerPoint slide