Insight into the synergism of residual carbon and slag particles in coal gasification fine slag on porous composites preparation for CO2 capture

Coal gasification fine slag (FS), as a by-product of coal gasification process, contains residual carbon (RC) and slag particles (SP). The two components can be used as raw materials to prepare porous materials. Whereas, during simultaneous utilization of RC and SP, their synergistic mechanism remains unclear. The research on the mechanism is beneficial for synthesis of the high performance CO2 adsorbent. Herein, FS was treated by chemical activation followed by hydrothermal treatment to prepare porous composite material (FS-25-HA-HT) which had high surface area of 2194 m2/g and pore volume of 2.095 cm3/g. After chemical activation, the SP could be completely dissolved in alkali solution within around 20 min. The adsorption of porous carbon in alkali solution and strong electrostatic attraction from oxygen groups with the Si, Al-containing groups led to the increase of the concentration of Si (9825 ppm) and Al (2986 ppm) in subnatant during hydrothermal treatment. Thus, the aluminosilicate could deposit on the surface of porous carbon and pile up to form new crystal layer, which could increase the surface area and the CO2 adsorption capacity. The adsorbent met both high uptake (5.32 mmol/g at 0 °C) and fast adsorption kinetics (adsorption equilibrium time of 3 min.). The clarification of synergism during simultaneous utilization of RC and SP offers new routes to prepare high performance adsorbent.